Procedures
RBD
VIRUS, PLAQUE
Participants received the assigned intervention (ie, intramuscular administration of one dose of CoronaVac or BNT162b2), during the enrolment and vaccination visit (day 0) at the community vaccination centre. CoronaVac is a Vero cell-based, aluminium hydroxide-adjuvanted, β-propiolactone-inactivated monovalent vaccine, and each 0·5 mL dose includes 600 SU of inactivated SARS-CoV-2. BNT162b2 is a nucleoside-modified mRNA monovalent vaccine encoding the trimerised SARS-CoV-2 spike glycoprotein formulated in lipid nanoparticles, and each 0·3 mL dose contains 30 μg of mRNA. Both vaccines were of the ancestral virus formulation. We collected 20 mL blood samples immediately before vaccination and scheduled follow-up blood draws at 28 days, 182 days, and 365 days after vaccination. In a voluntary subset of participants (Details of serological testing, including our in-house ELISA for the receptor binding domain (RBD) of the spike protein, a surrogate virus neutralisation test (sVNT; GenScript, Piscataway, NJ, USA) and a plaque reduction neutralisation test (PRNT), have been described in our earlier studies.