Zika Vaccine VLA1601

Zika Seroprevalence of 2.4% in Postpartum Women

Karen McClorey Hackett — Sat, 24 May 2025 10:31:44 +0000

Reviewer:

Over the past decade, the Zika virus has been found in over 50 countries and territories in the Region of the Americas.

As of May 24, 2025, Zika virus (ZIKV) remains a significant public health concern in Brazil, with over 11,500 cases reported this year.

While most people recover from this mosquito-transmitted disease, pregnant women and their unborn children may become infected, leading to serious health issues.

Researchers have stated that understanding population serological status, particularly in pregnant women, is vital for estimating the spread of this virus.

A research article published by the Journal of Medical Virology on May 21, 2025, assessed ZIKV seroprevalence in pregnant women and the transplacental transfer of antibodies to their newborns, crucial for early-life protection.

Effective transplacental transfer of specific ZIKV antibodies from mothers to newborns was observed.

A cross-sectional seroprevalence study was conducted with 601 postpartum women and their newborns in São Paulo city, Brazil, post-ZIKV fever outbreak.

Paired maternal and umbilical blood samples were collected for ZIKV antibody testing. ZIKV neutralizing antibodies (nAbs) were detected in 2.4% of these women.

Maternal and neonatal characteristics were associated with seropositivity for ZIKV and the antibody transfer to neonates. Maternal place of birth, parity, education level, and prenatal Toxoplasmosis serology were identified as risk factors associated with ZIKV infection.

Low seroprevalence of ZIKV antibodies in the study population indicates a high vulnerability to infection by these viruses.

The low ZIKV seroprevalence observed in this study contrasts sharply with higher rates reported in the Northeast of Brazil, with 63% in pregnant women in Salvador (2015–2016) and 30% among Bolivian blood donors (2016–2017).

This study's findings offer a comprehensive understanding of the antibody transfer dynamics in the context of ZIKV infection. This understanding is paramount, as it can potentially inform vaccine development strategies in endemic regions and guide the development of more effective neonatal infection prevention measures.

Published in JAMA Network Open in January 2025, a population-based study of mortality rates among 11.4 million children born with a severe Zika virus infection had a strikingly higher risk of overall and cause-specific mortality.

Young children with congenital Zika syndrome (CZS) had a 13-fold higher risk of death compared with those without CZS. This study found that the cause-specific mortality hazard ratio was 30.28.

The U.S. CDC's updated Yellow Book says healthcare professionals should know how to diagnose, treat, and prevent Zika in international travelers, especially pregnant women.

The CDC writes providers should 'carefully evaluate pregnant women with laboratory evidence of Zika virus infection; closely manage these patients during pregnancy and carefully evaluate live-born infants for clinical features associated with intrauterine infection.'

While an innovative Zika vaccine candidate is conducting clinical trials in 2025, no vaccine has been approved.

Researchers recently estimated that mosquitoes are carrying the Zika virus into new regions, and approximately 1.3 billion people could be affected by Zika by the year 2050.

The Pan American Health Organization writes, 'The decision to travel to a country with a history of Zika circulation should be based on a personal risk assessment, done in conjunction with the traveler's healthcare provider, that accounts for individual risk factors for severe outcomes from the possibility of a Zika infection.'

Sub Title:

Zika infection rates in women and infants vary by geography

Reference:

Seroprevalence and Placental Transfer of Zika and Dengue Virus Antibodies in Postpartum Women in Southeast Brazil

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Pregnant Women Should Not Visit Zika Outbreak Zones in 2025

Karen McClorey Hackett — Thu, 15 May 2025 17:35:24 +0000

Reviewer:

Robert Carlson, MD

Since the Zika virus disease (ZIKV) was first identified in 1947, outbreaks have often occurred in 92 countries around the world, adversely affecting the health of adults, children, and even unborn infants.

According to the World Health Organization (WHO), this mosquito-transmitted virus will continue to be a health risk for years.

Researchers estimate that mosquitoes are carrying the Zika virus into new regions, and approximately 1.3 billion people could be affected by Zika by the year 2050.

And without a Zika preventive vaccine available, outbreaks will continue to impact certain people severely, such as pregnant women, who have an increased risk of congenital malformations, such as microcephaly.

According to a study's results published by eClinicalMedicine on May 8, 2025, the pooled absolute risk of microcephaly at birth for newborns born to ZIKV-infected women ranged from 2.5% to 6.1%, depending on the analytical approach.

This study's data, which included 9568 pregnant individuals and 9608 newborns, indicated that the risk of severe primary microcephaly was significantly higher in ZIKV-positive pregnancies (1.5%, CI 0.8%–2.7%) compared to ZIKV-negative ones (0.3%, CI 0.1%–1.0%), with a relative risk of 4.5 (CI 1.5–13.3) in the one-stage meta-analysis.

These researchers wrote, 'Our findings can support planning actions to provide care to mothers who may become infected during pregnancy and their children. Women of reproductive age should be informed about the risks of Zika infection during pregnancy to support reproductive planning.'

Pregnant individuals should be offered testing and informed about potential risks to make informed decisions. Psychological support should be available, and children born to ZIKV-infected pregnant individuals should receive comprehensive evaluations for early diagnosis and management of congenital Zika manifestations.'

As of May 2025, the U.S. Centers for Disease Control and Prevention (CDC) Yellow Book states that international travelers with suspected Zika infection should be tested with real-time polymerase chain reaction or an NS1 antigen test.

Furthermore, the CDC says the decision to travel to a country with a history of Zika circulation should be based on a personal risk assessment conducted by the woman and her healthcare provider.

The CDC and the PAHO/WHO also issued various Travel Health Advisories, identifying countries reporting Zika cases, such as Argentina, Bolivia, Brazil, Colombia, Guatemala, and even the U.S. Territory of Puerto Rico.

Without a vaccine, avoiding mosquito bites is the best disease prevention tactic.

In the future, the most advanced Zika vaccine in clinical development, Valneva SE's VLA1601, may become U.S. FDA-approved.

Sub Title:

Zika infection during pregnancy can cause harm to infants

References:

Adverse fetal and perinatal outcomes associated with Zika virus infection during pregnancy: an individual participant data meta-

Microcephaly Prevalence in Infants Born to Zika Virus-Infected Women: A Systematic Review and Meta-Analysis

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Infant

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PAHO Zika map

South America's Zika Outbreaks Disrupt Summer Vacations

Karen McClorey Hackett — Thu, 03 Apr 2025 17:19:54 +0000

Reviewer:

Robert Carlson, MD

As of early April 2025, there is no active Travel Health Notice from the U.S. CDC to inform international travelers about health risks related to Zika virus outbreaks. This means thousands of travelers are visiting affected countries, unaware of the Zika's resurgence.

Since the peak of Zika in 2016, outbreak media coverage has significantly decreased, leaving travelers uncertain where to plan their next vacation.

To fill this information gap, the UK Travel Health Pro recently identified countries reporting unusually high mosquito-transmitted Zika cases.

By the end of 2024, 90 countries across Africa, Europe, the Americas, Southeast Asia, and the Western Pacific reported locally acquired cases of the Zika virus.

According to the Pan American Health Organization's Zika case dashboard as of April 3, 2025, Argentina, Brazil, and Bolivia are the South American countries with the highest number of Zika virus disease cases. In total, the Americas have reported 6,014 this year.

In Argentina, a total of 497 cases of Zika have been reported in 2025.

In Bolivia, 31 cases of Zika virus disease have been reported.

And in Brazil, a total of 5,517 Zika cases have been reported since the start of 2025. Last year, Brazil reported over 42,000 Zika cases.

Furthermore, the UK has confirmed that an increasing number of returning travelers have been infected with Zika. The most frequently reported country of travel was Thailand, followed by India.

In 2024, 16 Zika virus disease cases were reported in England, Wales, and Northern Ireland, a 100% increase from 2023.

The UK says most people infected with the Zika virus do not develop symptoms.

However, Zika infections in pregnant women can cause congenital Zika Syndrome, such as microcephaly and neurological complications, such as Guillain-Barré Syndrome.

These serious health concerns also apply to returning U.S. travelers, as 18 Zika cases were confirmed in 2024.

A recent discovery published in the journal Nature Communications helps explain why many people develop a weaker immune response to the Zika virus.

Published on March 25, 2025, these researchers identified the effects of Zika on the host T cell response, highlighting the need to factor such differences into the design of anti-flavivirus vaccines.

Since no approved Zika vaccines exist, the CDC and the UK advise travelers visiting Zika-endemic areas to avoid mosquito bites. Moreover, pregnant women are advised to postpone visiting at-risk regions.

This is one Zika vaccine candidate conducting clinical research, indicating another form of prevention is on the horizon.

Valneva SE's VLA1601 is a second-generation purified, inactivated, whole Zika virus vaccine candidate, conducting phase 1 research. Insights from this research are expected later in 2025.

Sub Title:

Zika infections can cause microcephaly and neurological complications, such as Guillain-Barré Syndrome

References:

UKHSA

Nature Communications March 2025

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US CDC Zika Case Map 2024

Most Countries Confirmed Fewer Zika Infections in 2024

Karen McClorey Hackett — Fri, 03 Jan 2025 10:44:43 +0000

Reviewer:

Robert Carlson, MD

Since first impacting people in the Region of America in 2014, the mosquito-transmitted Zika virus has affected many people's health. According to recent reports, most countries in the Americas reported fewer Zika outbreaks in 2024.

Additionally, a second-generation Zika vaccine candidate has progressed in clinical trial development for the first time.

As of January 3, 2024, the Pan American Health Organization (PAHO) confirmed the local transmission of Zika in countries and territories in the Americas region.

The PAHO reported over 41,942 ZIka cases and two related fatalities in the Americas in 2024, with the highest proportion of Zika cases reported in Brazil, Bolivia, and Columbia.

In December 2024, Brazil was the leading country reporting increased Zika cases. Brazil's Ministry of Health indicated over 40,000 cases in 2024, compared to 35,962 in 2023.

In the United States, the U.S. CDC only reported 19 non-congenital Zika cases in U.S. residents (1 imported case in Texas).

And in the U.S. Territories, Puerto Rico has been categorized as having a risk of Zika virus transmission for several years. As of December 2024, 16 Zika cases have been reported, a decrease from 2023, when 43 cases were reported.

Unfortunately, the Zika virus has been reported in several of India's 16 states/union territories, such as Maharashtra, for several years, and 2024 continued this trend.

To alert international travelers, the CDC issued a Level 2—Practice Enhanced Precautions regarding India's ongoing Zika outbreak in August 2024.

The CDC says most people infected with Zika will not have symptoms or mild symptoms, such as fever, rash, headache, joint and muscle pain, and red eyes. However, infection during pregnancy can cause certain birth defects, such as microcephaly.

From a disease prevention perspective, Valneva SE's VLA1601, a purified, inactivated, whole Zika vaccine candidate adsorbed on aluminum hydroxide, is the most advanced vaccine development in 2025.

Topline data from Valneva's phase 1 clinical trial (VLA1601-102) are expected in 2025. The company previously stated that it plans to accelerate vaccine approval discussions with government agencies like the U.S. FDA.

Sub Title:

Zika Cases in Costa Rica and Puerto Rico decreased in 2024

References:

US CDC Zika Cases 2024

Zika Travel Advisory - India

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from Pixabay 2025