LAMP1 and cytomegalovirus infection: Unlike the ChAdOx1 S-D cohort, only CMV-seropositive participants had an increase in CD107a expression at day 14 following ChAdOx1 vaccination (P = 0.0072), and there was a positive association between CMV infection and NK cell CD107a expression after ChAdOx1 vaccination (fixed effects analysis, P = 0.015 when accounting for time point and CMV serostatus; Figure 4C).