In this game, experience counts.
In 1977, a type of H1N1 virus, commonly known as the “Russian flu,” spread across the world, infecting people under 25 at much higher rates than their elders, who had been exposed to similar viruses in the ’40s and ’50s. In the first documented American outbreak, 70 percent of the students fell ill at a high school in Cheyenne, Wyoming, while their teachers proved immune.
It is likely that there are several factors at play here, but there is historical precedent for this sort of thing. If the swine flu circulating today is similar in certain ways to a previous strain, old people who came across it already will have an immunological advantage.
“Results among adults suggest that some degree of preexisting immunity to the novel H1N1 strains exists, especially among adults aged >60 years,” they wrote. “One possible explanation is that some adults in this age group have had previous exposure, either through infection or vaccination, to an influenza A (H1N1) virus that is genetically and antigenically more closely related to the novel influenza A (H1N1) virus than are contemporary seasonal H1N1 strains.”