- Influenza is caused by an RNA virus, which tends to mutate more quickly than DNA viruses.
It is necessary to have a new vaccine for influenza every year because the influenza virus is an RNA virus, which tends to mutate more quickly than DNA viruses. Influenza viruses undergo frequent changes in their surface proteins, which are used by the immune system to recognize and fight off the virus. These changes are known as antigenic drift and antigenic shift.
Antigenic drift refers to small, gradual changes that occur in the surface proteins of the virus over time. These changes can accumulate rapidly and result in a virus that is different enough from previous strains that the immune system may not recognize it. As a result, the vaccine from the previous year may not provide effective protection against the new strain.
Antigenic shift, on the other hand, refers to sudden and major changes that occur in the surface proteins of the virus. This can occur when two or more different strains of influenza viruses infect the same host and exchange genetic material, resulting in a new virus with a different surface protein. This type of shift can result in a pandemic if the new virus is highly contagious and there is little pre-existing immunity in the population.
To keep up with the constantly evolving influenza virus, new vaccines are developed each year to provide protection against the strains that are expected to be most prevalent during the upcoming flu season. These vaccines are designed based on surveillance data and predictions about the likely strains to be circulating in the population. Therefore, having a new vaccine each year is essential to providing effective protection against influenza.