Further analyses and sensitivity analyses
We only conducted VE analyses for CoronaVac because few other vaccines were used in the study population. We evaluated VE during the overall study period and separately for the period in which SARS-CoV-2 B.1.617.2 (delta variant) was predominant (1 July 2021 - 1 December 2021), which we defined using WGS data from study samples along with publicly available data from GISAID. We also performed these two analyses excluding participants who had a PCR-confirmed SARS-CoV-2 infection prior to enrolment. In addition, we examined VE since time since vaccination by comparing VE in the period from 14 – 149 days since the second vaccine dose to VE ≥150 days since the second vaccine dose.
We performed two sensitivity analyses. For the first, because reinfection can occur earlier than 90 days, we changed the definition of “time at risk” from 90 days after infection to 60 days after infection. For the second, because individuals may be protected as early as 7 days after their second dose, we defined “fully vaccinated” as 7 days after the second dose rather than 14 days after the second dose.