Daijiworld Media Network - Philadelphia

Philadelphia, Mar 15: A new study suggests that younger adults and children would derive greater benefits from H5N1 vaccines, even if they are not specifically designed for the currently circulating strain in birds and cattle.

Researchers from the University of Pennsylvania found that past exposure to seasonal flu viruses, especially H1N1 and H3N2, triggers cross-reactive immunity against the H5N1 avian influenza virus.

Published in Nature Medicine, the study revealed that older adults who were first exposed to flu viruses before 1968 possess higher levels of antibodies that can bind to the H5N1 virus.

“Early childhood influenza exposures can elicit immune responses that last a lifetime,” said Prof. Scott Hensley, highlighting that while these antibodies may not prevent infections, they could help mitigate severe disease in the event of an H5N1 pandemic.

The latest H5N1 strain, clade 2.3.4.4b, has spread among cattle but does not efficiently infect human upper airway cells. However, mutations from widespread circulation in mammals could enhance human transmissibility, raising concerns about a potential outbreak.

The study, which analysed blood samples from over 150 individuals born between 1927 and 2016, found that those born before 1968 had stronger immune responses to H5N1. In contrast, young children with limited exposure to seasonal flu viruses showed lower levels of protective antibodies.

Hensley cautioned that if an H5N1 pandemic occurs, all age groups will be vulnerable, but children may face the highest disease burden. “If this is the case, children should be prioritised for H5N1 vaccinations,” he asserted.