Post Reply - H2H-H5N1 spread in US

   https://www.nature.com/articles/d41586-024-02170-6

Older populations might be more protected than younger ones because of exposure to ‘matched’ strains during childhood, but an H5N1 pandemic is likely to take a major toll all the same.

Thus, people born before 1968 have tended to escape H5N1’s ravages, because they probably had their first flu infection at a time when the dominant flu virus in circulation matched H5N1. But people born after 1968 eluded the worst of H7N9, because their first encounter with flu was probably with a virus that matched it rather than H5N1. Immunity from a first infection provided 75% protection against severe disease and 80% protection against death with a matching bird-flu virus, the authors found.
If an H5N1 outbreak were to occur, this first-bout effect predicts that older people could once again be largely spared whereas younger people could be more vulnerable, Worobey says. “We should have that somewhere between the back and front of our minds,” he says.