In January 2025, the flu epidemic remains a pressing public health concern, particularly impacting vulnerable populations and the unvaccinated. Research reveals that a person’s birth year and initial flu exposure significantly influence lifelong immunity. A study highlights that individuals born before 1968 exhibit stronger resistance to certain flu strains, while those born afterward are better protected against others. This phenomenon, termed ‘immunological imprinting,’ underscores the importance of vaccination and preventive measures to protect at-risk groups during outbreaks.
The Ongoing Flu Epidemic and Its Impact
This January 2025, the flu epidemic continues to significantly affect the population, with hospitals witnessing a spike in severe cases, particularly among vulnerable groups and those who are unvaccinated. Understanding the intricacies of immunity against this ever-evolving virus has become crucial in navigating this public health crisis.
How Year of Birth Influences Flu Resistance
Recent research sheds light on how the year of your birth, along with your initial exposure to the flu virus, can shape your resistance to the illness over your lifetime. A compelling study from researchers at the universities of Arizona and California, published in the journal Science, underscores this relationship. Dr. Gérald Kierzek, the medical director at Doctissimo, elaborates on these important findings.
The study emphasizes the differences in ‘anti-flu protection’ for individuals born before or after 1968. It specifically examined two avian type A viruses, H5N1 and H7N9, both notorious for causing severe illness and fatalities in humans. By analyzing data on severe cases tied to these strains, researchers identified a notable correlation: the flu strain to which a person was first exposed during childhood influences their future immunity against new strains.
Dr. Kierzek notes, “Individuals born prior to 1968 appear to have heightened protection against certain group 1 flu viruses (like H5N1 and H1N1) while being more susceptible to group 2 viruses (such as H3N2 and H7N9). Conversely, those born post-1968 are generally better shielded from group 2 viruses but are more at risk for group 1 viruses.” This phenomenon is attributed to a mutation in the HA (hemagglutinin) antigens of flu viruses that occurred in 1968, marking a significant shift in dominant flu strains.
The impact of initial flu exposure, known as ‘immunological imprinting’ or ‘antigenic imprinting,’ hinges entirely on the first encounter with the flu virus during childhood. Researchers assert that this initial exposure, often occurring before the age of five, leaves a lasting imprint on the immune system. Dr. Kierzek explains, “Antigenic imprinting indicates that the first flu virus we encounter in childhood permanently influences our immune response.” To illustrate this concept, researchers liken flu antigens to lollipops of various colors and flavors.
Michael Worobey, one of the study’s authors, elaborates: “If your first exposure was to a flu virus resembling an ‘orange lollipop,’ encountering a different subtype later in life with similar ‘orange’ characteristics will likely provide cross-protection, lowering your risk of severe illness. However, if your initial experience was with a ‘blue lollipop,’ that protection won’t apply.” Despite these correlations, no year of birth guarantees complete immunity against the flu. Dr. Kierzek emphasizes, “This ‘protection’ related to your birth year is not absolute; vaccination is still highly recommended, particularly for vulnerable and elderly individuals. As we age, the presence of other health conditions and weakened immune systems (immunosenescence) can heighten vulnerability.” During an epidemic, it’s crucial to utilize strategies such as vaccination, practicing good hygiene, wearing masks, and frequent handwashing to help mitigate the spread of the flu and safeguard at-risk populations.