Sample size
SECONDARY
A sample size of 800 pupils and 400 staff at each school level (primary and secondary schools) was calculated to estimate the seroprevalence with a margin of error of 2.3% for pupils and 3.0% for staff, assuming a seroprevalence of 6% among pupils and 10% among staff and a cluster design effect of two. All participants were recruited during the first data collection period (December 2020/January 2021).