Vaccinated HCWs with no prior COVID infection (n = 9), asymptomatic recent infection (n = 10), and frequent recent infection (n = 15) were recruited from a longitudinal HCW cohort study. Blood was taken and exposed to SARS-CoV-2 antigens to measure the immune response. 2/8

What to expect? Upon primary infection, a delayed but robust response is expected. The virus could propagate more and a strong response is needed. Upon acquisition of immunity, the response is fast, less time for viral propagation, and a reduced response is needed. 3/8