Great question.
The answer in the link Akshat’s given is good, so I’ll just give you a simplified version if you can’t be bothered to read all that!
As you say, viruses change all the time, that’s so that the antibodies your immune system creates to fight them don’t work any more. It’s difficult to create a vaccine for any virus because they’re always changing, but sometimes the change is only small so vaccines are still effective.
Comments