Mexico Confirms Vaccine Coverage for Influenza A(H3N2) Subclade K

Mexico’s Ministry of Health says the influenza vaccine and antiviral treatments available in the country provide protection against influenza A(H3N2) subclade K, a strain that has expanded internationally and prompted alerts from global health authorities, while officials report only one confirmed case domestically.

David Kershenobich, Ministry of Health said Mexico’s response is focused on prevention through vaccination rather than emergency containment, noting that existing epidemiological data do not point to increased disease severity. The case identified in Mexico involved an 80-year-old patient who received outpatient treatment and recovered without complications. “The vaccine we have in Mexico covers this variant and helps prevent severe cases and hospitalizations,” said Kershenobich, emphasizing vaccination as the most effective strategy to reduce risk.

Influenza A(H3N2) subclade K has drawn international attention after the World Health Organization and the Pan American Health Organization reported a rapid increase in detections across Europe, East Asia and parts of North America. The subclade evolved from related J.2.4 strains and has accumulated genetic changes, including amino acid substitutions in the hemagglutinin protein. WHO has said these changes represent viral evolution rather than a shift toward greater clinical severity, with no significant increases observed in hospitalizations, intensive care admissions or deaths.

The strain became more prominent in Australia and New Zealand beginning in August 2025 and has since been identified in more than 34 countries over the past six months. In the European Union, it accounted for nearly half of reported influenza sequences during an early start to the season, while the United States and Canada have reported steady increases in detections. South America has remained largely unaffected to date, according to PAHO, although health authorities continue to monitor trends.

Against this backdrop, Mexican health officials have sought to reassure the public and business community that the country has sufficient tools to manage seasonal influenza risks. Kershenobich said the influenza vaccine used nationally, Mexinvac, has been administered since 2024 and is fully produced in Mexico. He added that supply levels are sufficient to cover priority populations and that antiviral treatments are also available nationwide.

“Prevention is much better than focusing only on treatment once the disease appears,” said Kershenobich. He noted that overall influenza case numbers in Mexico remain similar to those recorded in 2024, a year in which authorities attribute control of the season to vaccination coverage. As of mid-December, about 50% of the target population had been vaccinated, according to the Ministry of Health.

The ministry has reiterated its call to increase vaccination uptake as winter progresses. Priority groups for the seasonal campaign include children aged six months to five years, adults aged 60 and older, and people with underlying conditions such as diabetes, hypertension, obesity, asthma, chronic kidney disease or illnesses that compromise the immune system. Health authorities are urging eligible individuals to complete their vaccination schedules at health centers and authorized medical units.

In addition to vaccination, Mexico continues routine epidemiological surveillance through the National Epidemiological Surveillance System, including genomic sequencing to detect changes in circulating influenza strains. Officials say this monitoring framework enables the timely identification of the single subclade K case and supports early detection of any broader transmission.

International health agencies have encouraged countries in the Americas to strengthen genomic surveillance and ensure timely access to antiviral treatment as they prepare for the 2025–2026 influenza season. WHO and PAHO have also highlighted the importance of maintaining high vaccination coverage to protect vulnerable populations and reduce pressure on hospital systems, particularly if influenza activity begins earlier or intensifies.

Preliminary data cited by global health authorities suggest that, despite antigenic differences in subclade K, vaccine effectiveness against hospitalization remains comparable to previous influenza seasons. Estimates indicate effectiveness of roughly 70% to 75% in children and 30% to 40% in adults, reinforcing vaccination as a key tool in mitigating severe outcomes.

Mexico’s winter vaccination campaign also includes COVID-19 and pneumococcal vaccines, administered according to eligibility criteria. Health officials say the combined approach is intended to reduce the overall burden of respiratory disease during the winter period and prevent complications among high-risk groups.

The Ministry of Health has said it will continue to provide updates through official channels and maintain permanent epidemiological vigilance. While international monitoring of influenza A(H3N2) subclade K continues, Mexican authorities maintain that current conditions do not indicate elevated public health risk and that existing prevention and treatment measures remain adequate.