Question

What virus causes the flu? Why doesn't the body produce permanent immunity against that virus? How does the vaccine against the flu work?

Answer 1

The influenza virus causes the disease flu. This virus has mutation rate in DNA, which forms many different strains. The flu causes an epidemic in affected populations. Also, people get affected several times in their life time.

A body cannot produce immunity against these viruses. Once its produced, the virus gets mutated and the body is not immune against it. The immune response producing during previous infections is not effective in future infections.

Against the flue, the vaccine is prepared of the attenuated virus of three different strains. Each year, the research conducted by WHO provides which strains should compose the vaccine. This is the only strategy to combat the high mutation rate of these virus.