At present, the vaccine compatibility of the H3N2 subtype influenza virus has further improved compared to previous years, and the compatibility of the H1N1 and B influenza viruses is even higher. ”On November 10th, at a press conference held by the National Bureau of Disease Control and Prevention, Wang Dayan, a researcher at the Institute of Viral Disease Control and Prevention of the Chinese Center for Disease Control and Prevention, answered a question from a Science and Technology Daily reporter about the preventive effect of influenza vaccines, stating that the proportion of epidemic strains with antigenicity similar to vaccine strains exceeded 95%.

In response to the misconception among a small portion of the public that the flu virus is constantly mutating and cannot be prevented even with vaccination, Wang Dayan made it clear that although the flu virus is prone to mutation, the flu vaccine will be updated annually to match the current season's epidemic strains.

How can we increase the similarity between vaccine strains and epidemic strains to enhance the protective effect of vaccines? Wang Dayan introduced that the World Health Organization recommends influenza vaccine strains to the northern and southern hemispheres each year based on the influenza strains monitored worldwide for use in influenza vaccine production. The Chinese Center for Disease Control and Prevention monitors the epidemic intensity, pathogen changes, and trends of influenza through epidemiological and pathogen monitoring, providing scientific basis for vaccine strain screening and vaccine immunization strategy formulation.

Recently, the Chinese Center for Disease Control and Prevention released the "Technical Guidelines for Influenza Vaccination in China (2025-2026)". Compared with last year's influenza vaccine, the strain of influenza A H3N2 vaccine has been updated.

The influenza virus will constantly mutate, and antigen drift will occur during the transmission of the influenza virus, resulting in differences in the main epidemic strains during each influenza season compared to the previous year. Therefore, even if you received the flu vaccine last year, you still need to get vaccinated again before this year's flu season.

The flu vaccine, which seems to be administered repeatedly every year, actually contains vaccine components that are adjusted and updated every year, "said Zhang Ying, chief physician of the Tianjin Center for Disease Control and Prevention. The flu vaccine has better protection against seasonal viruses every year.

In addition, the antibodies produced after influenza vaccination usually decrease after 6-8 months, and the protective effect will also weaken accordingly. Zhang Ying said that the immune protection of influenza vaccine is time sensitive, and it is best to be vaccinated before the peak of influenza to provide sufficient time for the immune system to produce protective antibodies and exert the best protective effect during the peak of influenza. In fact, there are multiple peaks in the influenza virus epidemic process, so getting vaccinated during the entire influenza season is beneficial.

Wang Dayan stated that the overall prevalence of influenza in China is currently at a moderate level, with the A H3N2 subtype accounting for over 95%. There are also a small number of A H1N1 and B influenza viruses circulating simultaneously, and the proportion of different types and subtypes varies in different regions. Influenza activity is higher in southern provinces than in the north.

With the spread of the flu, many people believe that they have already contracted the flu and do not need to be vaccinated. Regarding this, Zhang Ying explained that even after contracting the flu, it is still necessary to receive the flu vaccine. Because the influenza virus family is very large, multiple subtypes of influenza viruses often circulate simultaneously or alternately during the same influenza season. One infection only produces antibodies to a specific subtype, and there is a lack of effective cross immunity between different subtypes of influenza viruses. Even if you get the flu once, there is still a risk of contracting other subtypes of flu viruses.

Jiao Zhenquan, Director of the Monitoring and Early Warning Department of the National Bureau of Disease Control and Prevention, emphasized that winter and spring are the high-risk periods for acute respiratory infectious diseases such as influenza in China. Recently, influenza activity has significantly increased and is expected to continue for some time. Relevant departments will strengthen prevention and control measures for key populations and institutions, and mobilize key populations such as the elderly, patients with underlying diseases, children, and medical staff to actively receive influenza, pneumococcal, and other vaccines; At the same time, during the high incidence period of respiratory infectious diseases, establish a dual notification mechanism for epidemic risks, strengthen the handling of clustered influenza like cases, reduce the risk of disease transmission, and prevent the spread of the epidemic.