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Incidence of symptomatic PCR-positive results (coprimary outcome) and incidence of all PCR-positive results (secondary outcome)
(A) Incidence of symptomatic PCR-positive results in students and staff by study group. (B) Incidence of all PCR-positive results in students and staff by study group. Weekly incidence is shown per 100 000 at risk. The shaded area is the mean rate plus or minus 1 SE using a negative binomial model to account for overdispersion (θ=0·28).
