Your year of birth may predict how likely you are to catch the flu later in life, says new research published in the journal Science.
Flu viruses acquired during one’s childhood make an imprint on the immune system – and that imprint can translate to health benefits many years later, report researchers from the University of California and the University of Arizona.
“Strains circulating during an individual’s childhood confer long-term protection against” viruses in later years, write the researchers.
Their discovery may have important implications for the health of the population in the face of future flu pandemics, and it could reshape how the medical community views childhood vaccines.
“These findings challenge the current paradigm, where the entire population would be immunologically defenseless in a pandemic caused by a novel influenza virus,” said Katelyn Gostic, a UCLA doctoral student and the lead author.
“Our results suggest it should be possible to forecast age distributions of severe infection in future pandemics, and to predict the potential for novel influenza viruses from different genetic groups to cause major outbreaks in the human population,” added Gostic.
Studying Flu Strains Across Generations
To gain their findings, the research team analyzed the health and demographic data of all known patients affected by two strains of avian flu – H5N1 and H7N9.
They noted that the two strains tended to affect different age groups. More H5N1 infections occur in children and young adults, while H7N9 more frequently affects older adults.
The researchers also pinpointed a moment in time – 1968 – that serves as something of a dividing line between age groups and whether they’re more likely to be infected by the H5N1 or H7N9 strain of avian flu. The so-called Hong Kong flu pandemic occurred that year and ushered in new strains that had unique similarities to the H7N9 strain.
Knowing that, the researchers found that people born in 1968 or after showed greater immunity to the H7N9 strain, while those born prior to 1968 were protected against the H5N1 strain.
“Our findings show clearly that this ‘childhood imprinting’ gives strong protection against severe infection or death from two major strains of avian influenza,” said James Lloyd-Smith, a UCLA professor of ecology and evolutionary biology. “These results will help us quantify the risk of particular emerging influenza viruses sparking a major outbreak.”
As flu strains mutate, a related change takes place among the human population at a wide level, explain the researchers. “When this community of related pathogens undergoes major shifts, as during influenza pandemics, the landscape of population immunity changes accordingly,” they write.
Understanding how the population adapts to changes in the ever-evolving strains of influenza may be instrumental in creating new and improved medical interventions.
“This approach opens new frontiers in the nascent field of quantitative risk assessment for emerging pathogens,” Lloyd-Smith said. “All of the focus has been on studying properties of the viruses and ecological circumstances that drive spillover. Those factors are definitely crucial, but it turns out we can learn a lot about flu pandemic risk from information about humans, which we’ve already got.”