The author of the story was telling us that in 1918 they didn’t have any vaccines to treat the infection so they could be protected from whatever virus was spreading. There is something inside our bodies that is called antibodies and what they do is if something that isn’t from your body they will fight back because they know that it isn’t from your body. So again the author was telling us about the past , like what happened and that they just didn’t have anything to cure the vicious influenza.