evidence: Immune response to vaccination after COVID-19 [...] To look at this question in a larger group of people, researchers led by Drs. Jonathan Braun, Susan Cheng, and Kimia Sobhani from Cedars-Sinai Medical Center used blood samples donated by healthcare workers at their hospital. The team measured levels of antibodies in the blood before vaccination and then after each of the two vaccine doses. They compared levels in people with prior COVID-19 infection with those who never had the virus. Blood samples were taken between 7 and 21 days after each vaccination. [...] "Overall, individuals who were previously infected with COVID-19 developed an antibody response after a single vaccine dose that was comparable to that seen after a two-dose vaccination course administered to individuals without prior infections," Sobhani says. "It appears that a single booster dose given to previously infected individuals offers the same benefit as two doses given to people without prior infection."