They are necessary for Pfizer and Moderna ...
First, know that if you are fully vaccinated, the CDC said you continue to be protected from infection and especially against serious illness. All the COVID-19 vaccine shots authorized by the FDA continue to be “highly effective in reducing risk of severe disease, hospitalization, and death,” according to the CDC.
However, recent studies — such as one from Israel and another from the UK — suggest that the effectiveness of COVID-19 vaccines may decrease after six or eight months and a booster shot may be needed to maintain high levels of protection against breakthrough COVID infections.