In the USA in 1978, they mandated VACCINATION and it resulted in a three fold increase in the reported incidence of whooping cough.
A group of researchers at the National Institutes of Health is trying to develop a vaccine that targets the tail of the hemagglutinin protein, the head of which is a part of the virus that mutates more rapidly with genetic drift. In a study published in Nature Medicine this May, the team reported it was effective in mice and partially effective in ferrets.
Why do you have to get a flu shot every year?
The flu is remarkably good at mutating. That's why it's so good at avoiding our body's defense mechanisms and keeps infecting us year after year.
The influenza virus not only undergoes small, usual changes through a process called antigenic drift; it also undergoes huge genetic changes through something called antigenic shift, where it mutates after passing through a carrier animal like a pig or a bird.
Because these processes alter the strains of flu that are circulating in the population every year, you have to get a new shot every year, too. The US Centers for Disease Control and Prevention analyzes the three or four strains that are most likely to be problematic each year, and then puts them in the annual vaccine.