COVID-19 shots weren’t studied in large numbers of people with weak immune systems. But limited data and experience with flu and pneumonia vaccines suggest they won’t work as well as they do in others. That means people with weakened immune systems should keep taking precautions like wearing masks and avoiding large crowds.
“It’s prudent to use all the precautions you were using before you were vaccinated,” said Dr. Ajit Limaye, a transplant expert at University of Washington Medicine in Seattle.