Fig. 2

Cohort description based on the ever-positive principle, i.e. anti-N sero-positivity remains for all rounds after sero-conversion, independently of other blood results or if missing. A Change of serological status of participants: only infected (anti-N ever positive and stated to be non-vaccinated in the questionnaire), naïve (anti-N and anti-S always negative), vaccinated (only anti-S ever positive), infected & vaccinated (in previous round only anti-S positive, or stated to be vaccinated in the questionnaire), infected without information on vaccination (infected, undefined vaccination) and non-responders/missing. B Observed responder behaviours. Left legend: number of participants. Right legend: number of missing rounds. Bottom legend: number of missing samples per round