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

Answer) Flu is the common name of Influenza. it is caused by three kinds of RNA viruses;

• Influenzavirus A
• Influenzavirus B
• Influenzavirus C

Influenza viruses are the RNA viruses, so their genome is frequently mutated which give rise to different serotypes of similar influenza viruses. the human body has certain innate immunity against the viruses. but, due to frequent mutation arising in the viral genome prevents the permanent immunity against that virus. in short, the body may not produce permanent immunity against that virus because of frequent mutations in the viral genome.'

Vaccines are prepared by the pharmaceutical companies against the most prevalent serotype of those viruses which is more prevalent in those years of vaccination. higher authorities of the United States and Europe issues the guidelines for "which is more prevalent serotype of flu viruses" in those years. based on the serotype, vaccines are developed. these vaccines are either attenuated serotypes of those viruses or their antigenic proteins. natural immunity is generated inside the body in the form of antibodies against these serotypes. such that those persons become immune to that flu virus.