I am a doctor and this is why your year of birth has an impact on your resistance to this virus

While the epidemic of flu current situation continues to strongly affect the population in January 2025, hospitals are facing an increase in serious cases, particularly among people at risk and the unvaccinated. This context recalls the importance of better understanding the mechanisms of immunity to this complex and evolving virus. A recent study offers fascinating insights into the role of the year of birth In resistance to influenza.

The year you were born and your first exposure to the flu virus would influence your resistance to this illness throughout your life. A study led by researchers at the Universities of Arizona and California, published in Sciencehighlights this impact. Dr Gérald Kierzek, medical director at Doctissimoexplains these findings.

Born before or after 1968: different “anti-flu protection”

The study focused on two avian type A viruses, H5N1 and H7N9, known to have caused many serious cases and deaths in humans. When examining data on severe cases and deaths associated with these two strains, researchers discovered a surprising link: The strain of flu that a person was first exposed to as a child would determine which new strains they would be protected against in the future.

According to Dr Gérald Kierzek, “People born before 1968 seem better protected against certain group 1 influenza viruses (H5N1, H1N1) but more vulnerable to group 2 viruses (H3N2, H7N9). It is the exact opposite for people born after 1968 : they are better protected against group 2 viruses, and more vulnerable to group 1 viruses. This phenomenon would be linked to a mutation in the HA (hemagglutinin) antigens of influenza viruses in 1968, a change that marked an important transition in the nature of the dominant strains.

The importance of first exposure to the flu

This effect, called “immunological fingerprint” or “antigenic fingerprint”, depends solely on first exposure to the influenza virus in childhood. According to researchers, this first encounter, often before the age of 5, leaves an indelible mark on the immune system. Dr. Gérald Kierzek specifies: “Antigenic fingerprinting suggests that the first exposure to a flu virus in childhood leaves a permanent mark on our immune system.” Researchers use a metaphor to clarify this mechanism. They compare flu antigens to lollipops of different colors and flavors.

“Let’s say you were first exposed to an ‘orange lollipop’ human flu when you were a child,” explains Michael Worobey, one of the authors of the study. “If later in life you encounter another subtype of flu virus that comes from a bird but whose proteins have a similar ‘orange’ flavor, your chances of dying are quite low due to cross-protection. But if your first flu was a ‘blue lollipop’, this protection will not apply.” However, no year of birth provides absolute protection against the flu. Dr. Kierzek recalls: “This ‘protection’ linked to the year of birth is not absolute and vaccination remains recommended, in particular for people at risk and elderly. With age, other underlying diseases make us vulnerable and the system immune system weakens (immunsenescence). During an epidemic, the vaccine, barrier gestures, wearing a mask and washing hands remain essential tools to limit the spread of influenza and protect populations at risk.

Passionate about women’s news, Agathe has been deciphering the latest trends for aufeminin since 2022. Her favorite areas? Psychology, nutrition and well-being advice, without forgetting the tips…