SLIP recommends vaccination or revaccination of at-risk groups during the development of vaccines adapted against H3N2 subclade K influenza.

High-risk patients who have not been vaccinated in 2025, recommend vaccination to prevent death.

The Latin American Society of Pediatric Infectious Diseases (SLAIDE) has prepared a guide containing vaccination measures and general recommendations.

Together with slip information

Vaccination remains the best public health intervention to reduce the clinical impact of the disease caused by the variant (subclade K) of the H3N2 influenza virus worldwide, highlighted the South American Society of Pediatric Infectology (SLIP), in publishing a guide to vaccination recommendations in the transition period from December 2025 to March 2026, when vaccines are available.

In general, they called for optimizing vaccination coverage for high-risk groups and people traveling to exposed areas, ideally two weeks before travel.

In the document, Epidemiological alert regarding the current variant of the H3N2 virus, they explain that subtype K is a genetic variant, which is a normal stage in the evolutionary process of the virus, which provides greater invasion power (acceptance) and an exception to the immune system.

"This is not a new pandemic, a new virus or a more serious or deadly flu. GISAID global data show that it originated in the United States and is found in more than 40 countries, including on every continent, although South America is the last affected region."

Slipe points out that "this variant of the influenza A virus (H3N2) is characterized by 7-9 escape mutations in hemagglutinin (HA) (K2N, N158D, I160K, T328A, Q173R, S378N, T135K, K189R) and S144R of the antibody."

However, "the current vaccine induces a durable immune response, specifically preventing hospitalization, severe pneumonia, and death."

Immunization Guide

La Slipe has shared vaccination guidelines for the transition from December 2025 to March 2026, pending the 2026 vaccine in the Southern Hemisphere (April).

In the case of normal-risk patients previously vaccinated in 2025, it is recommended that they not be revaccinated now because "they have basic protection against severity. An additional dose of an outdated vaccine does not significantly improve prevention of Clade K. 2 infection."

In the case of high-risk patients vaccinated in 2025, revaccination should be considered (travel to high-risk areas, patients with an interval more than six months.

"Current vaccines, although imperfect against mild infections, are highly effective in avoiding intensive care unit admissions. Manage existing vaccines for survival and plan mandatory boosters with up-to-date vaccines as soon as possible (2026).

The use of masks in closed spaces, respiratory etiquette, social distancing and hand washing are effective and preventive measures, Slipp said.

In addition, people returning to the country from areas with confirmed circulation of subclade K are advised to do so. When they have respiratory symptoms, they should wear a mask, isolate themselves and inform health services of their travel history.

We call for intensive epidemiological surveillance of acute respiratory infections and early detection and immediate notification of clusters and outbreaks, especially in closed populations (detention centers, shelters, nursing homes).

The promise of timely treatment: "Rapid diagnosis at the onset of symptoms is important, so that you can start treatment within 48 hours, for the full effectiveness of antiviral drugs and drugs that are available under different commercial names in the country, some of which are available in many countries (oseltamivir, zanamivir, baloxavir and peramivir)."

International and regional situation

La Slipe explained that currently most cases occur in Europe, Canada, America and Mexico, because these countries are in winter, which contributes to the spread of respiratory diseases.

Latin American countries such as Peru, Costa Rica, Brazil, Chile, Argentina and Panama have confirmed the identification of new strains, where in the last week the circulation of influenza B, influenza A(H1N1) pdm09 and to some extent seasonal influenza A(H3N2) has been recorded again with other respiratory viruses. Syncytial virus (RSV) and SARS-CoV-2.

"However, given the international air and sea traffic characteristic of Latin America, especially in the busiest cities such as São Paulo, Bogotá, Lima, Buenos Aires, Panama and Santiago de Chile, as well as in strategic ports such as Panama, Santos, Colon, Callao and Buenos Aires, it is unlikely that aircraft will not support either from the territory where passengers will fly. The expansion of this option and contribute to the spread of the disease."

Slipe does not rule out that this option will spread to other Latin American countries, since "real-time genomic sequencing is not routinely implemented in all countries of the region".

According to information from Slipe