Vaccine News

In recent years, Argentina has seen a significant rise in Zika virus infections. Both Argentina and its South American neighbor, Brazil, face challenges in diagnosing Zika infections and distinguishing them from Dengue fever, another disease transmitted by mosquitoes.

According to the Pan American Health Organization (PAHO), current efforts focus on improving the sensitivity of surveillance systems. In Argentina, Zika is detected mainly through passive surveillance systems that identify cases in people seeking medical care.

This detection process is not a guarantee that the Zika virus is not in circulation.

This makes it challenging to monitor the increasing number of Zika cases, which can lead to severe congenital disabilities, including microcephaly. This happens because an infected pregnant woman can spread the virus to her unborn baby.

As of December 12, 2025, the PAHO reported Argentina has confirmed 1,045 Zika cases this year.

This data compares with 564 reported in 2024.

Buenos Aires, the capital of Argentina, with over 3 million residents, and an international traveler's favorite, has seen a significant rise in Zika cases in 2025, with hundreds reported by the Health Ministry.

While the U.S. CDC has not issued a Travel Health Notice in 2025 focused on Zika outbreaks in Argentina, the PAHO and other organizations caution all visitors to reduce their risk of infection.

In the near term, a Zika prevention vaccine may be approved. Until then, beware of mosquito bites!

Connecticut's health department today reported its first measles case since 2021. This patient is an unvaccinated resident of Fairfield County, located just northeast of New York and home to about 950,000 people.

The Connecticut Department of Public Health (DPH) reported on December 11, 2025, that this child recently travelled internationally and began showing symptoms of measles several days later.

"The single best way to protect your children and yourself from measles is to be vaccinated," said DPH Commissioner Manisha Juthani, MD, in a press release.

"One dose of measles vaccine is about 93 percent effective, while two doses are about 97 percent effective. We must ensure we continue to protect those who matter most – children and other vulnerable people – from vaccine-preventable illnesses through on-time vaccination."

According to the 2024-2025 Statewide School Immunization Survey, 98.2% of Connecticut students had received two doses of MMR by kindergarten entry. Connecticut's MMR vaccination rate is one of the highest in the U.S.

MMR vaccination services are generally offered at clinics and pharmacies in the United States.

As schools and colleges begin their winter vaccinations in December 2025, many students are heading south to warmer weather.

One of the most popular destinations this year is the Republic of Costa Rica.

While the U.S. Centers for Disease Control and Prevention (CDC) highlights that routine vaccines, such as measles, are needed before traveling abroad, several mosquito-transmitted viruses are currently infecting people in Costa Rica.

The positive news is that fewer infections are being confirmed in this Central American country.

Moreover, infection risks vary by city, such as San Juan, in the central mountains, or at the beach.

On December 5, 2025, the Costa Rica Health Department's Boletín Epidemiológico N° 46 confirmed recent cases of Chikungunya, Dengue, Malaria, and Zika virus infections.

So far in 2025, eight cases of Chikungunya have been reported. Last year, over 40 cases were reported.

Over 5,400 Dengue cases were reported in 2025. About 31,200 cases were reported in 2024.

And 12 cases of Malaria had been reported in Costa Rica. In 2024, 200 cases were reported.

Furthermore, the seldon discussed, but very serious Zika virus has caused 11 cases, far fewer than the 32 reported in 2024.

Regarding accessing preventive vaccines before a trip to Costa Rica, a travel consultant is best suited to answer questions, as some vaccines are available globally but not in the United States. Other vaccines, such as those for Zika, are still in clinical trials in late 2025.

In the U.S., travel clinics such as PassportHealth commercially offer consulting sessions for international travelers.

The World Health Organization (WHO) today published a Disease Outbreak News (586) titled "Seasonal influenza Global situation." In the Northern Hemisphere, influenza activity has increased since October 2025, with influenza A viruses predominant among the viruses detected globally.

As of December 10, 2025, the WHO stated that early estimates suggest the influenza vaccine continues to protect against hospital attendance in both children and adults. However, its effectiveness against clinical disease during the current season remains uncertain.

The WHO added that even if there are some genetic differences between the circulating influenza viruses and the strains included in the vaccines, the seasonal influenza vaccine may still protect against drifted viruses and the other virus strains included in the vaccine.

Vaccination is still expected to protect against severe illness and remains one of the most effective public health measures. WHO continues to monitor global influenza activity and influenza viruses, supports countries in surveillance capacity, and updates guidance as needed.

The WHO and U.S. CDC say vaccinations remain essential for international travelers, especially for people at high risk of influenza complications and their caregivers.

In the United States, recent reports have identified states such as Louisiana that have seen upticks in flu-related cases.

A new educational video takes viewers inside the Global Polio Laboratory Network, the "eyes and ears" of polio eradication. It demonstrates how laboratories around the world detect, confirm, and genetically track polioviruses.

When watching this video, you will learn how organizations like Rotary and the World Health Organization have successfully reduced polio cases in Africa by approximately 99%.

Discover how new laboratories, faster sequencing techniques, and enhanced surveillance are contributing to the effort to eradicate polio.

These insights are crucial for guiding responses to polio outbreaks.

As of December 10, 2025, the U.S. CDC's Travel Health Notice identifies 32 countries where polioviruses have recently been detected, including several in Africa.

The CDC suggests that before any international travel, you make sure you are up to date on your polio vaccines. Adults who previously completed the full routine polio vaccine series may receive a single lifetime booster dose of IPV.

Globally, the nOPV2 polio vaccine has been administered over 2 billion times during the last few years.

In the United States, polio vaccination services are commercailly offered at travel clinics and pharmacies.

The University of Oxford announced today that it has launched the world's first Phase II clinical trial of a Nipah virus vaccine candidate in Bangladesh in partnership with the International Centre for Diarrhoeal Disease Research.

This study is essential, as a vaccine is urgently needed, as the disease can be fatal in up to 75% of cases. 

Funded by the Coalition for Epidemic Preparedness Innovations, this study will assess the safety and immune response of the ChAdOx1 NipahB vaccine in a region where the virus causes recurrent outbreaks.

The ChAdOx NipahB vaccine was manufactured for this clinical trial by the Serum Institute of India Pvt. Ltd., the world's largest vaccine manufacturer.

Professor Brian Angus, Professor of Medical Practice at the Nuffield Department of Medicine, University of Oxford and Chief Investigator of the trial at the Oxford Vaccine Group, commented in a press release on December 9, 2025, "Starting a Phase II trial in a country affected by regular Nipah outbreaks is a critical step in making sure this vaccine is both effective and relevant to the people who need it most."

"It's an essential part of ensuring equitable access to protection against emerging infectious diseases." 

Nipah virus is a deadly disease from the same viral family as measles, the paramyxoviruses.

The World Health Organization recognises it as a research priority due to its pandemic potential. Of the 750 cases recorded since 1998, there have been 415 deaths related to this virus.

First identified after an outbreak in Malaysia, the Nipah virus causes small outbreaks in Bangladesh almost every year. In India, seven outbreaks of the Nipah virus have occurred since 2001, primarily occurring in the southern and eastern regions, according to a study published by the journal Frontiers.

Over the past week, reports of influenza cases have been confirmed across the United States, with a few states reporting outbreaks.

According to the Walgreens Respiratory Illness Index on December 9, 2025, Louisiana, Puerto Rico, Hawaii, and Georgia are the most recent, unfortunate leaders reporting flu outbreaks.

Previously, the latest FluView published by the Centers for Disease Control and Prevention (CDC) reported that 2.9% of visits to healthcare providers in the prior week were for respiratory illnesses, up from 2.5%.

The best data from the CDC is that no influenza-associated pediatric deaths occurred during the 2025-2026 season. Last flu season, 287 pediatric deaths were reported.

With the peak influenza season fast approaching, the CDC encourages most people to get their annual vaccination as soon as possible.