Do people who have had COVID-19 need a second vaccine shot?

A new study suggests that there is a strong boost to the immunity of everyone who receives the first dose of an mRNA vaccine, including those who have previously had a SARS-CoV-2 infection. However, only people who have never had a SARS-CoV-2 infection appeared to benefit from the second dose. The scientists tracked not only antibody responses to vaccination but also the creation of memory B cells, which provide longer lasting immunity against infection. People who experienced particularly negative side effects from the vaccine — such as fever, headache, and muscle pain — had stronger immune responses.