A recent study suggests that younger adults and children will benefit the most from H5N1 vaccines, even those that are not specifically tailored to the current circulating strains of the virus in birds and cattle. The study, conducted by researchers from the University of Pennsylvania, found that prior exposure to certain types of seasonal influenza viruses can promote cross-reactive immunity against the H5N1 avian influenza virus.
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The study, published in Nature Medicine, shows that older adults who were exposed to seasonal flu viruses circulating before 1968 had higher levels of antibodies capable of binding to the H5N1 avian flu virus. This discovery highlights the importance of early childhood influenza exposures, which can trigger immune responses that last throughout a person’s life.
How Childhood Influenza Exposures Aid H5N1 Immunity
Scott Hensley, a Professor of Microbiology at the University of Pennsylvania, explained that antibody responses primed by earlier strains of influenza, such as H1N1 and H3N2, can cross-react to the current H5N1 virus circulating today. Although most of these cross-reactive antibodies cannot prevent infections, they could help limit disease severity in the event of an H5N1 pandemic.
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The study tested blood samples from over 150 people born between 1927 and 2016, focusing on antibodies targeting the stalk proteins of various influenza viruses, including H5N1. The results revealed that older adults exposed to seasonal flu viruses earlier in life had higher levels of antibodies that could effectively bind to the H5N1 virus. In contrast, children who had not been exposed to seasonal flu viruses displayed low levels of antibodies capable of fighting the H5N1 strain.
H5N1 Vaccine Prioritization for Children
While older adults seem to have some protection due to prior influenza exposures, the study suggests that children may face the highest disease burden in the event of an H5N1 pandemic. Hensley emphasized that all age groups would likely be highly susceptible to the virus. However, he stressed that children should be prioritized for H5N1 vaccinations if the virus starts spreading among humans, as they would be most vulnerable.
Understanding the Current Threat of H5N1
H5N1 viruses have been circulating in birds for many years, but a new strain—clade 2.3.4.4b H5N1—has recently emerged and spread among cattle. While this current H5N1 strain does not easily bind to receptors in the human upper airway, widespread circulation in mammals could lead to mutations that help the virus infect human airway cells, increasing the potential for human-to-human transmission.
Importance of Early Vaccination for Children
This study sheds light on the importance of prioritizing younger individuals, especially children, for H5N1 vaccinations, particularly if the virus evolves to become more transmissible among humans. Early childhood exposure to seasonal flu viruses plays a crucial role in shaping the immune response, and ensuring that children receive the proper vaccinations could help mitigate the impact of a potential H5N1 pandemic.
Key Takeaways:
- Younger adults and children are more likely to benefit from H5N1 vaccines, especially in the event of a pandemic.
- Prior exposures to seasonal influenza viruses can trigger immunity against H5N1.
- Older adults have some immunity due to exposure to earlier flu strains, but children are at higher risk in case of an H5N1 outbreak.
- The study stresses that children should be prioritized for H5N1 vaccinations to limit the disease’s spread and severity.
