Yellow Fever

Colombia's Yellow Fever Outbreak Threatens Urban Centers

Karen McClorey Hackett — Sat, 19 Apr 2025 10:14:40 +0000

Reviewer:

The ongoing outbreak of Yellow Fever in the Republic of Colombia has been progressively expanding in South America, particularly in regions such as the Amazon basin, the Magdalena River, and departments like Meta.

Furthermore, Yellow Fever (YF) outbreaks have been reported in areas where the disease had not historically occurred, including the municipality of Neira in Caldas, which is situated in the coffee-growing region.

Since September 2024, 75 YF cases and 34 deaths have been confirmed in Colombia, representing a fatality rate of 45%.

In 2025, YF cases are distributed in nine departments: Tolima (59 cases), Putumayo (7), Nariño (2), Caquetá (2), Huila, Vaupés, Cauca, Meta, and Caldas (1).

The total number of confirmed YF-related deaths in Tolima is 23.

"A new case has arrived in the municipality of Chaparral, and here we know we have a focus in the east, south, and north, but we have the solution at our fingertips, and that is vaccination," said Health Secretary Katherine Rengifo Hernández, in a media release on April 15, 2025.

"There are educational checkpoints in place, accompanied by law enforcement, following the directives of our governor."

Although urban transmission of yellow fever has not been reported in Colombia since 1929, there is a potential risk of re-emergence.

Urban areas located below 2,200 meters are at risk of being affected by virus-transmitting mosquitoes. However, with climate change, the range of mosquitoes is expanding.

For example, Bogotá, the Distrito Capital, has approximately 8 million residents and is located at an elevation of just 2,640 meters.

To alert residents and visitors, Columbia's National Government declared a YF public health emergency on April 17, 2025. The measure aims to protect the population's lives, contain the spread of the virus, and mitigate its potential impact on public health.

The Government's urgent call to citizens to get vaccinated against yellow fever was reiterated.

Since September 2024, the National Government has intensified its vaccination strategy. The age range for immunization has been expanded, starting at 9 months of age and including people over 59 years of age, with mass mobilizations in the affected municipalities.

And Health Promotion Entities were instructed to form and operate vaccination teams in coordination with the public and private networks in all affected territories.

According to the U.S. Centers for Disease Control and Prevention (CDC), yellow fever is a viral disease transmitted by the bite of infected mosquitoes. In the first 24 hours, symptoms such as fever, headache, and malaise may manifest. In the following 72 hours, symptoms often intensify with gastrointestinal symptoms such as vomiting, diarrhea, and abdominal pain.

Starting on the fifth day, signs such as jaundice (yellowing of the skin and eyes) and bleeding may appear, which can lead to death in unvaccinated individuals.

To alert the millions of international travelers who visit South America each year, the CDC issued a Level 2 Travel Health Advisory on April 15, 2025, highlighting areas in Bolivia, Brazil, Colombia, and Peru.

The CDC stated that travelers to these areas should get vaccinated at least ten days before traveling abroad.

As of April 19, 2025, the YF-VAX (Stamaril) vaccine is commercially available at travel clinics and pharmacies in the United States. And vaccination certificates, for entry into designated countries, are issued upon completion.

Sub Title:

Yellow Fever vaccination services offered at travel clinics and pharmacies in 2025

References:

Columbia National Government declares a national health emergency due to an increase in yellow fever cases.

YF - Level 2 - Practice Enhanced Precautions

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US CDC Yellow Fever Advisory April 15, 2025

Children May Need More Than One Yellow Fever Vaccination

Karen McClorey Hackett — Thu, 10 Apr 2025 19:54:21 +0000

Reviewer:

Robert Carlson, MD

In 2013, the World Health Organization (WHO) withdrew its recommendation for the yellow fever (YF) vaccine booster doses. However, new research supports the Brazilian National Immunization Program's recommendation for a booster dose of the vaccine at four years of age.

This vaccination policy change is vital for the Federative Republic of Brazil as it combats the spread of this severe mosquito-transmitted virus.

To assess the duration of vaccine-induced immunity, Plos Neglected Tropical Diseases published research on April 9, 2025, of a study cohort involving adults and children in an area in northeastern Brazil without wild-type YF virus circulation, but with a high incidence of other mosquito-transmitted orthoflavivirus, such as Zika.

This phase IV, uncontrolled cohort study was carried out in three municipalities in northeastern Brazil.

The 17DD strain of the (YF-VAX, Stamaril) vaccine was administered to children aged 9 months to 4 years and adults aged 18 to 50 years. Blood samples were collected for antibody titration before vaccination, 30–45 days after vaccination, and one year post-vaccination.

This study showed that YF seroconversion rates 30–45 days after vaccination increased with age, reaching 99% in adults. However, 10% of infants did not have detectable antibodies.

These findings are the first to examine a cohort of vaccinees with serological follow-up in an area without YF viral circulation.

In summary, these researchers wrote, 'Current recommendations assuming lifelong protection from a single dose of the YF vaccine do not appear to provide sufficient protection in high-risk areas, particularly where infants are the primary target for vaccination.'

These findings align with a previous cross-sectional study, which found that 76.4% of children were seropositive between 9 and 23 months after vaccination. In addition to showing lower seroconversion rates, children aged 9–12 months had significantly lower antibody titers over time, with seropositivity dropping below 60% four years after vaccination.

According to the U.S. Centers for Disease Control and Prevention (CDC), yellow fever vaccination is recommended for people aged nine months or older who are traveling to or living in areas at risk for the YF virus, such as Brazil and Colombia.

The 17D yellow fever vaccine was initially approved for human use in 1938, and about 850 million doses have been distributed..

In the United States, the YF-VAX® vaccine is commercially available at travel clinics and pharmacies in April 2025.

Sub Title:

Yellow Fever vaccination services offered in the United States in 2025

Reference:

Immunogenicity of a single dose of the 17DD yellow fever vaccine in a cohort of adults and children

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US CDC 2025

Yellow Fever Fatality Rate Increases 20%

Donald Hackett — Wed, 12 Mar 2025 17:44:50 +0000

Reviewer:

Robert Carlson, MD

Over the past few centuries, yellow fever outbreaks have led to numerous cases and related fatalities. While the World Health Organization says most severe yellow fever (YF) cases have a fatality rate of around 39%, recent data from South America indicates an unfortunate increase in deaths.

Since 2024, the Republic of Colombia has faced an active YF outbreak. As of February 21, 2025, 40 cases have been confirmed (17 in 2025), with 19 related deaths, representing a case fatality rate (CFR) of 47%.

As of mid-March 2025, Columbia's YF outbreak remains active in the departments of Tolima, Caquetá, Huila, Nariño, Putumayo, and Vaupés.

Throughout South America, between the last months of 2024 and the first weeks of 2025, the Pan American Health Organization (PAHO) reported 61 cases of YF, 30 of which resulted in death, for a CFR of 49%.

These increased CFRs are similar to those reported between 2022 and 2023 in Bolivia, Brazil, Colombia, and Peru.

According to the PAHO, one factor in the approximate 20% increase in CFR is the expanded geography of YF-transmitting mosquitos.

The PAHO recently issued an epidemiological alert regarding a change in the geographic distribution of the YF disease. All cases had a history of exposure in areas at risk for the YF virus, such as wild and wooded areas, in the context of work activities that included agriculture, and had no documented vaccination history.

Another factor is that these new areas are unprepared to diagnose and treat YF infection before the infection worsens.

"A single case of yellow fever can constitute an outbreak, as it can spread rapidly. Therefore, one of the ways this disease is monitored is by observing how it behaves in nature. When non-human primates begin to become infected and die, this alerts us to the activity and potential spread of the virus, and allows us to anticipate epidemics in humans," explained Jairo Méndez Rico, Regional Advisor for Viral Diseases at PAHO's Department of Health Emergencies in a media release on March 11, 2025.

Various studies have determined that mosquito-borne diseases such as YF, chikungunya, dengue, and malaria are expanding their range and re-emerging in areas where they had subsided for decades. The extent to which climate change influences the population at risk of mosquito-borne diseases varies across altitudes.

In March 2025, the PAHO and the U.S. CDC continue encouraging everyone visiting a yellow fever endemic area to be protected by vaccination. YF vaccines have been found safe and effective and are commercially available at certified travel clinics and pharmacies in the United States.

Sub Title:

Yellow Fever outbreak in Columbia's Tolima, Caquetá, Huila, Nariño, Putumayo, Vaupés Departments

References:

PAHO strengthens integrated epizootic and vector surveillance of yellow fever in Colombia

Estimating case fatality risk of severe Yellow Fever cases: systematic literature review and meta-analysis

Projecting the risk of mosquito-borne diseases in a warmer and more populated world

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Can Fractional Yellow Fever Vaccinations Decrease Deaths in the Americas

Karen McClorey Hackett — Fri, 21 Feb 2025 10:09:57 +0000

Reviewer:

Robert Carlson, MD

While the Yellow fever vaccine has been found highly effective when administered as a single dose, researchers have continued to examine the minimum dose requirements for seroconversion.

These researchers say the potential advantages of offering fractional doses are increased vaccinations and reduced under-vaccination, which have become a measurable health concern in the Region of the Americas over the past few years.

For example, 61 human cases of yellow fever were confirmed in the Region of the Americas in 2024, of which 30 were fatal (case fatality ratio, 50%).

According to a new study, fractional dosing can protect people similarly to a full dose.

On February 19, 2025, the NEJM published an Orginal Article that concluded that Institut Pasteur de Dakar 17D-204 yellow fever vaccination fractional dose of 500 IU was noninferior to the standard dose of 13,803 IU for producing seroconversion within 28 days.

Noninferiority was shown if the lower boundary of the 95% confidence interval for the difference in the incidence of seroconversion between the fractional dose and the standard dose was higher than -10 percentage points.

Previously, The Lancet Infectious Diseases published an Opinion on April 28, 2023, saying fractional dose yellow vaccination in an emergency or reactive mass vaccination campaign has become essential in stretching the limited vaccine stockpile over a much larger population.

The Lancet also published results from a clinical study in January 2021 (updated Feb. 2022), concluding, 'Fractional doses of all WHO-prequalified yellow fever vaccines were non-inferior to the standard dose in inducing seroconversion 28 days after vaccination, with no major safety concerns. These results support using fractional dosage in the general adult population for outbreak response in a vaccine shortage.'

Moreover, the WHO's initial position on fractional yellow fever vaccine was set out in the 2013 position paper.

According to the Pan American Health Organization (PAHO) rapid risk assessment on February 14, 2025, yellow fever under vaccinations remains a public health concern.

Between 2014 and 2023, yellow fever vaccine coverage declined in about half of the countries with yellow fever endemic areas in the Americas. Six countries had less than 80% coverage: Argentina, Bolivia, Brazil, Panama, Peru, and Venezuela.

This under-vaccination rate is associated with the increase of yellow fever cases in late 2024 and the beginning of 2025 in endemic countries of the Americans, such as Brazil and Columbia.

PAHO says the overall risk of this event in the Americas Region, especially in endemic countries, is classified as ¨High¨ with a ¨High¨ level of confidence based on the available information.

Regardless of the vaccine's dosage, the PAHO and the U.S. Centers for Disease Control and Prevention recommend international travelers be fully protected against the mosquito-transmitted Yellow fever virus before visiting endemic areas in 2025.

In the United States, travel clinics and pharmacies offer the U.S. FDA-approved yellow fever vaccine YF-VAX.

Sub Title:

Yellow Fever Vaccine Fractional Dosage Found Protective

References:

Low-Dose Yellow Fever Vaccine in Adults in Africa

Public Health Risk Assessment related to yellow fever: implications for the Americas Region

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WHO 2025

Arriving at Juan Santamaria International Airport Has Enhanced Requirements

Karen McClorey Hackett — Sat, 08 Feb 2025 11:21:08 +0000

Reviewer:

Robert Carlson, MD

Arriving at the Republic of Costa Rica's Juan Santamaria International Airport (SJO) may include a few arrival requirements for Spring Break 2025. Last year, over 2 million people visited Costa Rica's beaches and mountains, many traveling from the United States.

As of February 8, 2025, the Costa Rican Ministry of Health and the U.S. Embassy in San Jose recently issued travel advisories to inform visitors of some changes.

Beginning in 2025, Costa Rica's Ministry of Health has enforced an expanded yellow fever vaccination requirement for all travelers from designated high-risk countries arriving at SJO. This enhancement is designed to bolster the country's public health defenses against the potential spread of the mosquito-transmitted yellow fever virus.

This yellow fever certificate (ICVP) requirement policy was first implemented in 2007, was enhanced on October 16, 2024, and became effective on January 11, 2025.

According to the Health Ministry, foreigners who arrive in Costa Rica and do not present the ICVP for either YF-VAX or Stamaril vaccination to the SJO immigration authority may not be allowed to enter the Central American country.

Countries now considered at risk and for which yellow fever ICVP is required include, but are not limited to, Bolivia, Brazil, Colombia, Ecuador, Guyana, French Guiana, Paraguay, Peru, Suriname, Venezuela, Trinidad and Tobago, and certain countries in Africa.

Since the YF vaccine is not part of the mandatory Costa Rican vaccination schedule, it must be purchased commercially at pharmacies or travel clinics.

In addition to YF, Costa Rica recommends that visitors protect themselves against the Chikungunya, Dengue, and Zika viruses.

Local chikungunya cases were confirmed throughout 2024 and already in 2025.

To prevent disease, Valneva SE's IXCHIQ® chikungunya vaccine has been approved and is available in numerous countries this year.

Furthermore, the U.S. Embassy recently announced travel incident reports have occurred near the SJO airport.

As of February 5, 2025, the Embassy recommends that visitors use caution when frequenting this area. If confronted on a trip to or from SJO, do not stop; continue progressing forward and contact 911 when it is safe.

Previously, the U.S. State Department issued a Level 2: Exercise Increased Caution Travel Advisory for Costa Rica, which states that visitors should exercise increased caution due to various civil unrest targeting tourists.

The local Embassy says that whether you reside in Costa Rica or are visiting for a week, you should enroll in our Smart Traveler Enrollment Program so that we can better assist you in an emergency.

Sub Title:

Costa Rica recommends yellow fever vaccination in 2025

References:

An amendment to Ministerial Resolution No. DM-CB-3109-2018 of July 20, 2018

Alert: Caution Traveling Near Juan Santamaria International Airport

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Juan Santamaria International Airport 2025

Yellow Fever Outbreak Alert Issued for the Americas

Karen McClorey Hackett — Tue, 04 Feb 2025 18:58:38 +0000

Reviewer:

Robert Carlson, MD

With the unexpected increase in human cases of yellow fever in the Americas region between the end of 2024 and the beginning of 2025, the Pan American Health Organization / World Health Organization (PAHO/WHO) issued an Epidemiological Alert.

Today, these health agencies stated, 'The risk of (continued) yellow fever outbreaks is high in the Americas Region.'

As of February 3, 2025, this Alert revealed that between epidemiological week (EW) 1 and EW 4 of 2025, 17 confirmed human cases of yellow fever (YF) had been reported in three countries in the Region, seven of which were fatal.

These cases have been reported in Brazil, Colombia, and Peru.

Additionally, Guyana has reported three laboratory-confirmed cases in 2025.

Furthermore, if projections are fulfilled, this YF outbreak may impact countries such as Argentina and Paraguay.

Last year, 61 human cases of yellow fever were confirmed in the Americas Region, of which 30 were fatal.

The PAHO/WHO calls on Member States with areas at risk to take the necessary actions to ensure that travelers visiting places where yellow fever outbreaks occur and vaccination is recommended are appropriately informed on how to prevent this mosquito-transmitted disease.

The PAHO/WHO wrote, 'It is essential that countries achieve vaccination coverage of at least 95% in populations in at-risk areas, in a homogeneous manner, and that health authorities ensure that they have a strategic reserve inventory that allows them to maintain routine vaccination and, at the same time, respond effectively to possible outbreaks.

"This report from PAHO and WHO serves as a reminder to travelers planning a visit to South America in 2025 of the importance of vaccinating against yellow fever because infection can lead to death in up to 60% of cases," stated Jeri Beales, MSN, RN.

"Thankfully, the yellow fever vaccine has proven highly effective, although some people with certain health conditions may not be eligible for vaccination."

"Keep in mind, if you plan to transit between multiple countries while in South America, the yellow fever vaccine may be required, and you need to bring the official yellow fever vaccination record with you, added Beales, the leader of Destination Health Clinic, a Boston-area travel health provider specializing in health education and vaccination for international travelers.

In February 2025, certified travel clinics and pharmacies in the United States will offer yellow fever vaccines to international travelers visiting these countries.

Moreover, Brazil's Ministry of Health recently warned international travelers about a potential need for a yellow fever vaccine booster dose.

Sub Title:

Travelers visiting yellow fever outbreak countries should consider vaccination in 2025

Reference:

Yellow fever in the Americas Region - 3 February 2025

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Yellow Fever Vaccine Boosters Suggested When Visiting Sao Paulo

Karen McClorey Hackett — Mon, 03 Feb 2025 16:27:45 +0000

Reviewer:

Robert Carlson, MD

The Ministry of Health of the Federative Republic of Brazil recently warned international travelers about an increase in the transmission of the yellow fever virus, which is expected to continue until May 2025.

As of February 2, 2025, this yellow fever (YF) warning is particularly relevant for the Brazilian states of São Paulo, Minas Gerais, Roraima, and Tocantins.

This travel alert is essential for São Paulo, which welcomed over 2.2 million tourists last year and may account for most of Brazil's yellow fever cases in 2025.

The São Paulo State Health Department is investigating suspected and confirmed yellow fever outbreaks in the city of Ribeirão Preto.

The Health Ministry wrote, 'People planning to travel to areas where yellow fever is transmitted or to rural and forested regions should check their vaccination records."

"Those who have not yet been vaccinated or received a fractional dose in 2018 should seek out a health unit at least ten days before traveling to get immunized and avoid exposure to the virus without protection.'

To combat future yellow fever cases and fatalities, Brazil's Ministry of Health has decided to increase the distribution of the yellow fever vaccine (Stamaril) in 2025. Sao Paulo state will receive two million doses, with an additional 800,000 doses by the beginning of February.

In 2024, the Ministry of Health distributed 20,882,790 vaccine doses throughout Brazil.

Last year, the Pan American Health Organization confirmed over 50 yellow fever cases, including 24 deaths, in the Region of the Americas.

In 2017, the U.S. CDC expanded its vaccination (YF-Vax) recommendations for travelers to Brazil in response to a large YF outbreak in the country's eastern states.

In 2025, the CDC says travelers older than 9 months going to the state of São Paulo, including the city of São Paulo and all coastal islands, consider vaccination.

"If traveling from the U.S. to Brazil, Yellow Fever is not required for entry. However, if you visit other countries after leaving Brazil, the vaccine may be required for entry," Duellyn Pandis, DNP, APRN, FNP-C, informed Vax-Before-Travel News.

"The YF vaccine is considered a lifetime vaccine, but the CDC and other health ministries encourage a booster after 10 years if traveling to an area with high YF activity, such as São Paulo."

"It's recommended to get vaccinated before you travel to an endemic country region country requirements,' added Pandis, President of Passport Health-Tampa.

The CDC also recommends that visitors to Brazil speak with a travel vaccine expert about chikungunya and typhoid vaccination options, especially those staying with friends or relatives or visiting smaller cities or rural areas. Furthermore, several regions in Brazil are reporting cases of Oropouche.

Sub Title:

Yellow fever travel alert Issued for São Paulo, Minas Gerais, Roraima and Tocantins

References:

Brazil technical note - Yellow fever 2025

Brazil Ministry of Health issues alert for increase in yellow fever

US CDC 2025

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Brazil Ministry of Health Feb. 2, 2025

Yellow Fever and Pneumococcal Conjugate Vaccines Mix Well

Karen McClorey Hackett — Thu, 16 Jan 2025 16:56:37 +0000

Reviewer:

Robert Carlson, MD

When international travelers plan to visit a country that requires proof of yellow fever (YF) vaccination, other vaccines may be administered at travel clinics to protect the person from disease.

Because booster doses of pneumococcal conjugate vaccine (PCV) may be given at a similar time to yellow fever vaccine, researchers believed it essential to assess the immune response to YF when co-administered with PCV.

An early release of a study published in the journal Vaccine (Volume 47), February 15, 2025, showed no evidence of the non-inferiority of the seroresponse to the YF vaccine when co-administered with PCV13.

The levels of YF NA attaining seroprotection (NT ≥1:8) were high (85%+) in all groups. PCV13, co-administered with the YF vaccine, does not affect the seroresponse to the YF vaccine.

In 2024, the World Health Organization (WHO) confirmed the yellow fever virus had become endemic in tropical areas of Africa and countries in the Region of the Americas. And 194 WHO member countries have introduced the YF vaccine into their routine Essential Programme on Immunization programs.

For example, Costa Rica recently expanded its proof of vaccination requirements.

In this Central American country, the YF vaccine is given as a single dose, generally at 9 months of age. It is often co-administered with the measles/rubella vaccine and the oral polio vaccine.

While some studies have shown no decrease in YF vaccine seroresponse when co-administered with measles/rubella vaccines, other studies have reported a decreased seroresponse against YF vaccines.

This research was supported by the Bill & Melinda Gates Foundation [grant number OPP1138798].

As of January 16, 2025, yellow fever vaccinations with Sanofi Pasteur's YF-VAX® are offered at travel clinics and pharmacies in the United States. Additionally, several next-generation yellow fever vaccine candidates are conducting clinical trials.

Sub Title:

Immunogenicity of yellow fever vaccination co-administered with 13-valent pneumococcal conjugate vaccine produces Positive results

Reference:

Immunogenicity of yellow fever vaccine co-administered with 13-valent pneumococcal conjugate vaccine in rural Gambia: A cluster-

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Hajj 1445 Pilgrims Were Well Protected from Disease

Karen McClorey Hackett — Mon, 07 Oct 2024 18:32:31 +0000

Reviewer:

Robert Carlson, MD

The annual Hajj pilgrimage to the Kingdom of Saudi Arabia (KSA) is the largest religious mass gathering in the world. Over the past two decades, up to 3.2 million pilgrims from more than 180 countries have gathered annually in Saudi Arabia for the Hajj.

These pilgrims arrive in Makkah and Madinah from diverse backgrounds, traveling to a confined geographic area, coupled with the close proximity and interactions among them, heightening the potential for spreading infectious diseases and posing unique challenges for public health management and disease control.

In 2024, the Saudi Ministry of Health remained vigilant in monitoring global disease outbreaks and recommend immunizations and preventive measures for the Hajj.

Published by the Journal of Infection and Public Health, Volume 17, Issue 11, November 2024, this review examines current trends in communicable diseases and their impact, drawing insights from expert perspectives on the required (e.g., meningococcal meningitis, polio, and yellow fever) and recommended vaccinations (influenza, COVID-19) for Hajj 1445 participants.

The updated COVID-19 vaccine is mandatory for local pilgrims and strongly recommended for international visitors. Discussions are ongoing on adapting protocols to address emerging variants.

The timing and strain coverage of influenza vaccination, along with quadrivalent meningococcal vaccination, are also emphasized as critical preventive measures.

Diseases such as cholera and yellow fever are addressed, underscoring the need for rigorous surveillance and targeted vaccination strategies to mitigate the risk of transmission during the Hajj.

The continued identification of novel infectious diseases, such as the Middle East Respiratory Syndrome Coronavirus (MERS-CoV), has also prompted modifications to the annual vaccination requirements for the Hajj pilgrimage.

Recently, the WHO Disease Outbreak News confirmed that five MERS-CoV cases, including four deaths, were reported from KSA in 2024.

This review aims to empower pilgrims and healthcare professionals to make informed decisions regarding public health and disease prevention during this significant event by providing up-to-date information on mandated and recommended vaccinations.

The review, posted online on September 30, 2024, provides a comprehensive overview of the vaccinations required and recommended for Hajj pilgrims, taking into account emerging infectious diseases and disease trends.

Seperately, the U.S. CDC publishes its list of recommended and required vaccinations for the 9,500 Americans performing Hajj.

Sub Title:

Mandatory and recommend vaccinations required when visiting the Kingdom of Saudi Arabia

References:

Hajj vaccination strategies: Preparedness for risk mitigation

Hajj Vaccinations 1445

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2024 World Population Review

Vaccine Certificates Can Curtail Yellow Fever Outbreaks

Karen McClorey Hackett — Thu, 26 Sep 2024 18:18:15 +0000

Reviewer:

Robert Carlson, MD

Since 1970, yellow fever has re-emerged as a public health threat in the Region of the Americas, and the risk of yellow fever outbreaks remains high in 2024.

This mosquito-transmitted, acute viral hemorrhagic disease has become endemic in 13 countries in Central and South America.

It is a substantial health risk to about 32 million visitors to South America this year.

On September 19, 2024, the Pan American Health Organization (PAHO) reported five countries in the Americas had confirmed 38 yellow fever cases, 19 of which were fatal.

Peru is the hardest-hit country, with 18 cases and nine deaths confirmed in various departments this year.

These yellow fever cases were all males between 18 and 83 years of age and had a history of exposure to wild and/or wooded areas due to agricultural work activities.

Unfortunately, these men had no yellow fever vaccination records.

Additionally, the PAHO reported that Bolivia, Brazil (3 cases, two deaths), Colombia, and Guyana are the other South American countries reporting cases in 2024.

Although immunization is one of the most successful public health interventions to prevent this disease, most cases reported during 2024 do not have a history of yellow fever vaccination.

Yellow fever has a unique status in the International Health Regulations (2005), which outline requirements for proof of vaccination for people who travel to specific countries or enter some countries from an area where yellow fever is endemic.

To prevent the importation of disease, many countries require proof of vaccination against yellow fever before issuing a visa, mainly if travelers come from or have visited yellow fever-endemic areas.

The U.S. CDC lists South American countries that are endemic to yellow fever.

The PAHO says countries must guarantee vaccination coverage greater than or equal to 95% in the populations of at-risk areas. Health authorities should ensure that they have a strategic reserve inventory that allows them to maintain routine vaccination and, at the same time, respond to possible outbreaks.

In 2023, over 60 million individuals received vaccinations under the WHO's Eliminate Yellow Fever Epidemics strategy.

The U.S. CDC says Sanofi Pasteur's YF-VAX® vaccine is safe and highly effective and is recommended for most travelers aged nine months and older.

Vaccination provides effective immunity within 30 days for 99% of those vaccinated. A single dose can confer sustained immunity and life-long protection without a booster.

"The CDC also recommends that travelers heading to regions experiencing yellow fever outbreaks should consider receiving a booster dose if it has been over ten years since their last vaccination," says Duellyn Pandis, DNP, MS, APRN, FNP-C, Certificate in Travel Health®.

"Certain people should not receive the vaccine, and waivers can be provided," added Pandis, President & CEO of Passport Health-Tampa. "To determine what is best for you, schedule an appointment 4-6 weeks before departure."

YF-Vax is only offered at certified travel vaccine clinics and pharmacies in the U.S.

Note: This news article was updated on Sept. 29, 2024, regarding the U.K. Foreign, Commonwealth & Development Office issuing a 'refrain from visiting Peru' travel advisory regarding health risks.

Sub Title:

Yellow fever vaccination offered at certified travel clinics and pharmacies

Reference:

Yellow fever in the Americas Region -19 September 2024

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PAHO Yellow fever case map Sept. 2024

66 Million People Vaccinated Against Yellow Fever in Africa in 2023

Karen McClorey Hackett — Wed, 03 Apr 2024 19:51:16 +0000

Reviewer:

Robert Carlson, MD

From early 2023 until late February 2024, 13 countries in the WHO African Region reported yellow fever (YF) cases.

Unfortunately, preliminary data suggests that the case fatality rate for yellow fever in these countries is 11%.

According to the World Health Organization, Burkina Faso, Cameroon, the Central African Republic, Chad, the Republic of the Congo, Côte d'Ivoire, the Democratic Republic of the Congo (DRC), Guinea, Niger, South Sudan, Togo, and Uganda continue reporting YF cases in 2024.

And Nigeria's outbreak has become a significant concern.

To alert international travelers, the U.S. Centers for Disease Control and Prevention (CDC) issued a Level 2 Travel Health Advisory on March 28, 2024, confirming yellow fever cases remain elevated in Nigeria after an outbreak was first reported in November 2020.

Since January 2023, several states in Nigeria have reported yellow fever cases (see map).

As of December 2023, the Nigeria Centre for Disease Control reported 600 suspected cases of yellow fever in 36 states and 273 Local Government Areas.

There are no medications to treat or cure yellow fever, so the CDC recommends that travelers to Nigeria avoid these areas unless vaccinated.

According to WorldInfo, Nigeria recorded about 518,000 tourists in 2021, ranking 68th in the world in absolute terms. Abuja is the capital of Nigeria, located in the center of the country, within the Federal Capital Territory, and is home to over 700,000 residents.

Response activities are underway, and mass vaccination campaigns are planned in the affected areas. According to the CDC, visitors should be vaccinated at least ten days before arrival.

The Eliminate Yellow Fever Epidemics secretariat coordinated preventive and reactive efforts during 2023, substantially enhancing vaccination coverage in Africa.

Approximately 62 million people were vaccinated in Africa through preventive and reactive mass vaccination campaigns. Additionally, under catch-up campaigns in Sudan, approximately 4 million individuals received vaccination against yellow fever.

In Africa, the Stamaril® vaccine is generally available. Stamaril is expected to offer protection from yellow fever for at least ten years.

Yellow fever is caused by a virus transmitted through bites of infected mosquitoes.

The urban proliferation of Aedes spp. mosquitoes bite during the day and can significantly amplify disease transmission risks, particularly in densely populated areas.

About 15% of people infected with the yellow fever virus will develop severe illness that can lead to liver disease, bleeding, shock, organ failure, yellowing skin (jaundice), and sometimes death, says the CDC.

In the U.S., various clinics and pharmacies offer Sanofi Pasteur's YF-VAX® vaccine.

Sub Title:

Stamaril yellow fever vaccine protects people for about ten years.

References:

WHO Disease Outbreak News Yellow fever – African Region 2024

CDC Travel Neath Notice - Nigeria - March 2024

Nigeria Centre forDisease Control 2023

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US CDC Travel Alert - Nigeria - March 2024

Yellow Fever Fatalities Reactivate in The Americas

Karen McClorey Hackett — Wed, 27 Mar 2024 17:47:09 +0000

Reviewer:

Robert Carlson, MD

Holly Lutmer PharmD

As international travel rebounds in 2024, the Region of the Americas is expected to receive about 10% more visitors than in 2019. While this is excellent news for the tourism industry, disease outbreaks are also being reported.

In the Americas, there is a high risk of yellow fever outbreaks in 2024.

According to the Pan American Health Organization (PAHO), this mosquito-transmitted viral hemorrhagic disease poses a significant challenge to healthcare professionals. Any delayed recognition of yellow fever's signs and symptoms, which can often be nonspecific and may resemble other acute febrile syndromes, can lead to fatalities.

As of March 19, 2024, there have been seven confirmed cases of yellow fever, including four fatal cases reported in the Region of the Americas this year.

In 2023, four countries in the Region reported 41 confirmed cases of yellow fever, including 23 deaths. These countries include Bolivia (5 cases, including 2 deaths), Brazil (6 cases, including 4 deaths), Colombia (2 cases, including 1 death), and Peru (28 cases, including 16 deaths).

To reduce the 2024 outbreak, the PAHO/WHO reiterated recommendations such as these:

Since the yellow fever vaccine is sufficient to confer lifelong immunity, universal vaccination in children in endemic countries at 12 months of age,
Administered an approved vaccine (Stamaril®) simultaneously with the measles, rubella, and mumps vaccine,
Endemic countries should vaccinate populations in at-risk areas, reaching at least 95% coverage,
Ensure all visitors to endemic areas are vaccinated at least ten days before arrival,
And have a reserve vaccine inventory in case of outbreaks.

Jeri Beales, MSN RN with Destination Health Travel Clinic near Boston, MA, offered these comments to Precision Vaccinations regarding individuals with travel plans who need the yellow fever vaccine: "The data shared by PAHO reminds travelers and health care providers of the serious and often life-threatening risks of traveling to a yellow fever region without appropriate vaccination."

"All but two countries in South America have some risk of yellow fever disease, but no countries require the vaccine for passengers arriving from the United States."

"This leaves many travelers planning an adventure of a lifetime without realizing they will visit a yellow fever region."

"Speak to your provider's office or travel clinic at least several weeks before your planned trip to check if the yellow fever vaccine is needed."

In the January 22, 2024, issue of The Lancet Global Health, Jenny Schnyder and colleagues presented the results of a systematic review and meta-analysis assessing the long-term immunity provided by a single dose of a licensed yellow fever vaccine in people living in areas both endemic and non-endemic for yellow fever.

The authors wrote that in non-endemic areas, a single dose in adults resulted in high seroprotection rates over time (pooled seroprotection rate 94% [95% CI 86–99]), thus providing life-long protection for travelers.

And in endemic areas, adult vaccination resulted in somewhat lower seroprotection rates (76% [65–85]).

However, the studies from endemic areas were all conducted in Brazil and generally used a higher threshold for the definition of seroprotection, which could explain the differences.

However, lower seroprotection rates were found in children (47%) and in people living with HIV (61%), indicating a potential need for booster vaccination in these groups.

To date, there is no indication of waning protection in populations vaccinated in early childhood. But, the YF-VAX® should not be given to individuals who have experienced a severe allergic reaction to eggs, egg products, or any vaccine component.

In the United States, the YF-VAX vaccine is offered at certified clinics and travel pharmacies.

Sub Title:

Yellow fever vaccination required for many travelers in 2024

References:

Epidemiological Update Yellow fever in the Region of the Americas - 21 March 2024

The life-long protective immunity of yellow fever vaccination: time to review?

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Yellow fever case detection South America map 2024

Yellow Fever Outbreaks Cause 11% Case Fatality Rate

Karen McClorey Hackett — Wed, 20 Mar 2024 19:15:38 +0000

Reviewer:

Robert Carlson, MD

Since the ancient Yellow Fever virus was identified in Africa centuries ago, the continent has reported extensive, deadly outbreaks.

In 2023, this unfortunate trend continued.

The World Health Organization (WHO) today published Disease Outbreak News confirming that the African Region continues to confront Yellow Fever outbreaks.

Since the beginning of 2023, and as of late February 2024, a total of 13 countries in the WHO African Region have documented probable and confirmed cases of yellow Fever.

As of March 20, 2024, the WHO's preliminary data indicates a case fatality rate of 11%.

While the overall risk at the African regional level was re-assessed as moderate and the global risk remains low, active surveillance is required due to the potential for onward transmission through international travel and the presence of the competent vector in neighboring regions.

Yellow Fever is an epidemic-prone mosquito-borne vaccine-preventable disease transmitted to humans by infected mosquitoes, notably Aedes sp. and Haemagogus species.

The urban proliferation of Aedes spp. These mosquitoes bite during the day and can significantly amplify transmission risks, particularly in densely populated areas, leading to swift yellow fever outbreaks.

The WHO-led global Eliminate Yellow Fever Epidemics (EYE) secretariat coordinated preventive and reactive efforts during 2023. Approximately 62 million people have been vaccinated in Africa through vaccination campaigns.

The WHO, the European Medicines Agency, and the Pan American Health Organization say a single yellow fever vaccination can grant life-long protection and promote sustained immunity for about 90% of people vaccinated.

The U.S. CDC says Yellow Fever vaccination is generally not recommended in areas with low potential for virus exposure.

However, vaccination might be considered for a small subset of travelers to these areas who are at increased risk for exposure to the virus because of prolonged travel or heavy exposure to infected mosquitoes.

The CDC says that any traveler's vaccination must consider the traveler's risk of being infected with the virus, country entry requirements, and individual risk factors for serious vaccine-associated adverse events.

"The yellow fever vaccine is a safe and highly effective way to prevent infection from what can be a deadly illness," Jeri Beales, MSN, RN, informed Precision Vaccinations. Beasles provides travelers with health information and vaccinations at Destination Health Travel Clinic near Boston, MA.

"This mosquito illness can spread rapidly between people, especially in urban areas where the mosquito has adapted to live, which is why some countries in Africa require proof of vaccination to enter."

"Children as young as nine months can be protected, and after vaccination, you may experience mild arm soreness, pain at the injection site, and sometimes a low-grade fever."

As of March 20, 2024, the YF-VAX® vaccine is licensed in the U.S. and available at certified travel vaccine clinics and pharmacies.

And the Stamaril® vaccine is available internationally in about 40 countries.

Sub Title:

African Region Yellow Fever outbreaks March 2024

References:

WHO - Disease Outbreak News Yellow fever – African Region March 2024

Yellow Fever: Origin, Epidemiology, Preventive Strategies and Future Prospects

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US CDC yellow fever outbreak map Africa

610,000 Individuals Receiving Yellow Fever Vaccine in South Sudan

Karen McClorey Hackett — Wed, 14 Feb 2024 23:24:53 +0000

Reviewer:

Robert Carlson, MD

In response to the yellow fever outbreak in late 2023, the Republic of South Sudan's Ministry of Health announced today that it has initiated a reactive yellow fever vaccination campaign as a preventive response intervention.

As of February 3, 2024, 48 suspected and two confirmed yellow fever cases were reported from Yambio, Nzara, Tambura, Ibba, Ezo, and Maridi Counties of Western Equatoria State.

"To address the (yellow fever) outbreak, a multidisciplinary team of epidemiologists, public health officers, entomologists, laboratory specialists, and risk communication experts conducted an extensive epidemiological investigation to characterize the extent of the outbreak, identify risk/exposure factors, and implement control and prevention measures," stated Honourable Yolanda Awel Deng, Minister of Health in a press release.

Targeting approximately 610 000 individuals aged nine months to 65 years in Yambio, Tambura Ezo, Ibba, and Maridi, the vaccination campaign utilizes doses secured from the Global emergency yellow fever vaccine stockpile of the International Coordination Group on Vaccine Provision.

Dr Humphrey Karamagi, World Health Organization (WHO) Representative for South Sudan, emphasized on February 13, 2024, "The yellow fever vaccination campaign aligns with the global strategy to Eliminate Yellow Fever Epidemics by 2026."

"This reactive measure aims to protect high-risk populations and act as a bridge towards integrating the yellow fever vaccine into routine immunization systems."

About 80 million yellow vaccine doses are produced annually. In the U.S., the YF-VAX® vaccine is licensed and available in 2024.

According to the WHO, yellow fever is a vaccine-preventable acute viral hemorrhagic disease that poses a significant public health threat. Characterized by symptoms such as fever, headache, jaundice, muscle pain, nausea, vomiting, and fatigue, the disease can lead to severe complications, with approximately half of patients succumbing within 7 to 10 days.

As of February 2024, the WHO says about forty-seven countries in Africa and the Americas are either endemic to or have regions endemic to yellow fever. Upon arrival, various countries require visitors to prove they have been vaccinated against yellow fever.

The U.S. recognized South Sudan as a sovereign, independent state on July 9, 2011, following its secession from Sudan.

Currently, the U.S. Department of State says, 'Do not travel to South Sudan due to crime, kidnapping, and armed conflict, as the U.S. government has limited ability to provide emergency consular services to U.S. citizens in South Sudan.'

Sub Title:

Yellow fever disease is vaccine preventable in 2024

Reference:

South Sudan Launches Yellow Fever Vaccination Campaign

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WHO Africa South Sudan map 2024

Are Yellow Fever Vaccine Boosters Needed

Donald Hackett — Tue, 06 Feb 2024 16:31:11 +0000

Reviewer:

Robert Carlson, MD

Holly Lutmer PharmD

A recently published review aimed to assess the necessity of a booster vaccination based on the long-term immunogenicity of primary yellow fever vaccination.

Overall, these researchers found that most primary vaccine recipients maintain neutralizing antibodies above protective thresholds ten or more years post-vaccination.

In healthy adults in non-endemic settings, who were primarily travelers, this systematic review and meta-analysis observed high rates of seroprotection 10–60 years post-vaccination (overall seroprotection rate 94%).

Published on January 22, 2024, these findings support the International Health Regulations, stating that single-dose yellow fever vaccination provides lifelong protection for travelers.

However, in people living with HIV and young children, booster doses might still be required because lower grades of protection were found.

Additionally, lower protection rates were observed among residents of endemic areas in Brazil.

Furthermore, because the yellow fever vaccine is contraindicated while using immunosuppressive drugs, no advice is provided by guidelines concerning booster vaccination in this situation.

The complete, unedited study is posted at this The Lancet Global Health link.

Jeri Beales MSN, RN, at Destination Health Travel Clinic, a CDC Yellow Fever vaccination site near Boston, MA., spoke with Precision Vaccinations on February 6, 2024, and stated, "This study adds further evidence that a single dose of yellow fever vaccine provides long-term immunity and backs up the decision in 2016 by the International Health Regulation to recommend a one time dose of yellow fever officially."

"Because yellow fever can sometimes become a deadly illness, it does warrant talking to a travel health specialist before your next trip to endemic areas."

Yellow fever is an acute febrile hemorrhagic and mainly zoonotic disease caused by the yellow fever virus, belonging to the genus Flavivirus, says the U.S. CDC.

Yellow fever is endemic in sub-Saharan Africa and South American tropical regions, where outbreaks have been reported, such as in Brazil.

Various countries in these regions require proof of vaccination before arrival.

As of February 6, 2024, the YF-VAX® vaccine is offered in the United States at certified clinics and pharmacies. The U.S. CDC says a yellow fever vaccine booster dose is unnecessary.

Other countries offer various yellow fever vaccines.

Sub Title:

Yellow fever vaccination are required by certain countries in 2024

Reference:

Long-term immunity following yellow fever vaccination: a systematic review and meta-analysis

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Cell Press 2024