"Super vaccine" is coming! The development of a universal vaccine that can fight multiple influenza viruses is expected to

Influenza (flu for short) is an acute respiratory disease caused by influenza virus and is a Class C infectious disease. Influenza virus is prone to mutation, highly contagious, and the general population is susceptible to it, with a high incidence rate. It is an important public health issue of global concern. It is more common in winter and spring in my country. Most influenza patients usually recover on their own within 3 to 14 days, but severe cases may be life-threatening. According to the World Health Organization, seasonal influenza can cause 3 million to 5 million severe cases and 290,000 to 650,000 deaths worldwide each year.

Flu vaccination is an effective way to prevent influenza virus infection and its serious complications. However, since there are many types of influenza viruses and they are prone to mutation, different flu vaccines are needed every year to cope with the influenza strains prevalent that year. Whether a universal flu vaccine can be developed to prevent all influenza, save medical resources and facilitate the public is the direction that scientists have been working towards.

New research opens up the possibility of developing a broadly protective flu vaccine

Scientists at the University of Pittsburgh School of Medicine have discovered a previously unrecognized class of antibodies in human blood that appear to neutralize multiple forms of influenza viruses. This latest research may be the key to developing vaccines that target seasonal viruses and provide broad protection. The paper, titled "A new class of antibodies that overcomes a steric barrier to cross-group neutralization of influenza viruses," was published in the journal Public Library of Science Biology on December 21.

The research team explained that the flu vaccine can prompt the immune system to produce antibodies. The antibodies can bind to the hemagglutinin viral protein on the outside of the invading flu virus, preventing it from invading human cells. Different antibodies bind to different parts of the hemagglutinin in different ways, but the hemagglutinin itself evolves over time, producing new flu strains that can evade old antibodies. Therefore, pharmaceutical manufacturers provide new flu vaccines every year based on predictions of the main strains.

For this reason, researchers are developing flu vaccines that protect against multiple strains at once, with a focus on antibodies that protect against both H1 and H3 influenza subtypes, which contain multiple strains and are responsible for the most widespread flu infections in people.

In the latest study, Holly Simmons' team found a small change in some H1 strains in the hemagglutinin building block sequence - 133a insertion. Studies have shown that some antibodies that can neutralize H3 can also neutralize H1. But if the hemagglutinin undergoes the above small change, the antibody cannot neutralize H1.

In a series of experiments on patient blood samples, the team also discovered a new class of antibodies that can neutralize some H3 strains and some H1 strains, regardless of whether the 133a insertion is present. Unique molecular features set these antibodies apart from other antibodies that can neutralize both H1 and H3 strains.

The research team pointed out that people need to be vaccinated against influenza virus once a year to keep up with the continuous evolution of the virus. The latest research shows that it is possible for humans to produce a strong antibody response to neutralize different H1N1 and H3N2 viruses, which opens up new ways to design better vaccines to deal with influenza viruses. What are the influenza vaccines currently approved for sale in China?

At present, there are three main types of influenza vaccines approved for marketing in my country, namely trivalent inactivated influenza vaccine (VII3), quadrivalent inactivated influenza vaccine (VII4) and trivalent live attenuated vaccine (LAIV3). Among them, VII3 includes split vaccine and subunit vaccine, VII4 is split vaccine, and LAIV3 is attenuated vaccine. At present, the World Health Organization and the Chinese Center for Disease Control and Prevention's "Technical Guidelines for Influenza Vaccination in China" clearly point out that there is "no priority recommendation" for the type of influenza vaccine. That is, any type of influenza vaccine can provide effective protection, and any type of influenza vaccine can be selected, but the applicable population varies (see Table 1 for details).

Table 1 Applicable populations for the three types of vaccines

Note: VII3 is a trivalent inactivated influenza vaccine; VII4 is a quadrivalent inactivated influenza vaccine; LAIV3 is a trivalent live attenuated vaccine

It should be noted that there is currently no influenza vaccine for infants under 6 months old. People aged ≥ 6 months can voluntarily choose according to their actual situation. It is recommended to vaccinate as much as possible, especially medical staff; vulnerable groups and employees in crowded places such as nursing homes, long-term care institutions and welfare homes; teachers and students in kindergartens, primary and secondary schools, and personnel in prisons and other detention institutions; the elderly over 60 years old, children aged 6 months to 5 years old, caregivers of infants under 6 months old, pregnant women or female patients who may become pregnant during the peak influenza season and have chronic diseases that affect immune function, etc.

Generally, within 2 weeks of receiving the flu vaccine, the body can produce antiviral immunity, and then this protective effect will gradually decay over time. Clinical studies have found that the protective immunity produced after vaccination with inactivated influenza vaccine usually lasts for 6 to 8 months, and significantly decreases after one year. Therefore, the flu vaccine needs to be administered every year, and regardless of whether it was administered in the previous season, it is still recommended to be administered before the flu season arrives.