If you look at the pandemic of 1977, when H1N1 or Swine Flu re-emerged after a 20 year absence, there is no shift in age-related mortality pattern. The 1977 “pandemic” is, of course, not considered a true pandemic by experts today, for reasons that are not entierely consistent. It certainly was an antigenic shift and not an antigenic drift. As far as I have been able to follow the current events, the most significant factor seems to have been that most people, who were severely affected, were people with other medical conditions.