Pfizer and Moderna Vaccines Likely to Produce Lasting Immunity

The findings add to growing evidence that most people immunized with the mRNA vaccines may not need boosters, so long as the virus and its variants do not evolve much beyond their current forms — which is not guaranteed. People who recovered from Covid-19 before being vaccinated may not need boosters even if the virus makes a significant transformation.

The results suggest that a vast majority of vaccinated people will be protected over the long term — at least, against the existing coronavirus variants. But older adults, people with weak immune systems, and those who take drugs that suppress immunity may need boosters; people who survived Covid-19 and were later immunized may never need them at all.

Exactly how long the protection from mRNA vaccines will last is hard to predict. In the absence of variants that sidestep immunity, in theory, immunity could last a lifetime, experts said. But the virus is clearly evolving.