H5N1 Danger: Why Kids and Young Adults Are at Highest Risk!

New Delhi: Younger adults and children would benefit the most from H5N1 vaccines, even if they are not specifically designed for the current strain circulating in birds and cattle, according to a new study.

Researchers from the University of Pennsylvania in the US found that prior exposure to certain seasonal influenza viruses helps develop cross-reactive immunity against the H5N1 avian flu virus.

Antibody Responses and Early Exposure

The study, published in Nature Medicine, revealed that older adults exposed to seasonal flu viruses before 1968 were more likely to have antibodies capable of binding to H5N1.

“We know that early childhood influenza exposures can elicit immune responses that last a lifetime,” said Scott Hensley, Professor of Microbiology at the University of Pennsylvania.

He further explained, “We found that antibody responses primed by H1N1 and H3N2 viruses decades ago can cross-react with H5N1 avian viruses circulating today. While most of these cross-reactive antibodies cannot prevent infections, they will likely limit disease severity if an H5N1 pandemic occurs.”

The Threat of H5N1 Mutations

H5N1 viruses have been circulating in birds for years, but a newer strain—clade 2.3.4.4b H5N1—has recently spread among cattle. While this strain does not easily bind to receptors in the human upper airway, mutations due to widespread circulation in mammals could enhance its ability to infect human airway cells and increase transmission.

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If these mutations occur, H5N1 could potentially begin spreading from human to human.

Vaccine Implications and Study Findings

Current influenza vaccines primarily generate antibodies that target hemagglutinin proteins, preventing infections.

In their study, researchers tested blood samples from over 150 individuals born between 1927 and 2016. They found that people born before 1968, who were likely first exposed to H1N1 or H2N2 in childhood, had higher levels of antibodies binding to the stalk of the H5N1 virus.

Additionally, birth year was closely linked to the number of H5N1-fighting antibodies in the bloodstream. Young children with no prior exposure to seasonal flu viruses had low levels of these antibodies.

Prioritizing Children for Vaccination

Scott Hensley emphasized that in the event of an H5N1 pandemic, all age groups would likely be highly susceptible, but children could face the highest disease burden.

“If this is the case, children should be prioritized for H5N1 vaccinations,” he said.