New Study Examines Why Some Fare Better with the Flu Than Others

A new study examines why some individuals are able to fight off the flu better than others. The answer, in part, may lead back to childhood.

Scientists believe the first flu strain we encounter in childhood-and the sequence of the strains we encounter throughout life-may have an effect on our body’s response to the flu virus, according to a study published in PLOS Pathogens.¹

Scientists from UCLA and the University of Arizona discovered that individuals who were first exposed to H1N1 were less likely to be hospitalized if they encountered that same strain again later in life than those who were first exposed to H3N2.

Those who were first exposed to H3N2 fared better against H3N2 over time than those who first encountered H1N1, according to the findings.¹

James Lloyd-Smith, PhD, a senior author of the study and professor of ecology and evolutionary biology at UCLA, believes this is because the 2 strains come from 2 separate branches of the influenza “family tree.”²

“Our findings emphasize that childhood exposures can imprint a lifelong immunological bias toward particular influenza subtypes, and that these cohort-specific biases shape epidemic age distributions,” the authors wrote.² “As a consequence, newer and less ‘senior’ antibody responses acquired later in life do not provide the same strength of protection as responses imprinted in childhood.”

Although H2N2 is a close relative of H1N1, the scientists also found that those who were exposed to H2N2 first as a child did not have greater immunologic protection against H1N1 later.

 “Our immune system often struggles to recognize and defend against closely-related strains of seasonal flu, even though these are essentially the genetic sisters and brothers of strains that circulated just a few years ago,” lead author Katelyn Gostic said in the release.²

To conduct the latest study, scientists used health records from the Arizona Department of Health Services. The records included those from hospitals and private physicians.

Influenza viruses continue to affect millions each year. According to the CDC, there have been an estimated 34 million to 49 million cases of influenza in the United States from October 2019 to February 2020.³

During that same time period, there have been between 20,000 and 52,000 flu-related deaths.³

Researchers hope that by factoring in which subtype of flu is circulating, they may be able to predict which age groups will be more severely impacted and better prepare a response.

References:

1. Lloyd-Smith JO, Gostic KM, Bridge R, et al. Childhood immune imprinting to influenza A shapes birth year-specific risk during seasonal H1N1 and H3N2 epidemics. PLOS Pathogens. 2019. Doi: https://doi.org/10.1371/journal.ppat.1008109

2. First childhood flu helps explain why virus hits some people harder than others [news release]. UCLA’s website. https://newsroom.ucla.edu/releases/why-flu-hits-some-people-harder-than-others.

3. CDC. 2019-2020 US Flu Season: Preliminary Burden Estimates. CDC’s website. https://www.cdc.gov/flu/about/burden/preliminary-in-season-estimates.htm.