In 1976 I was working in the Gulf Country around Cape York, in an aboriginal community of about 300 people. The Health Department sent around a team and vaccinated about 100 of them against flu. Six were dead within 24 hours or so and they weren't all old people, one man being in his early twenties. They threw the bodies in trucks to take to the coast where autopsies were done. It appeared they had died from heart attacks.