ABSTRACT
SARS-CoV-2 Omicron subvariant BA.2 is increasing in some areas of the world and it is important to assess how well current vaccines may protect against this infection. BioNTech Pfizer (BNT162b2) and CoronaVac are widely used COVID-19 vaccines globally. We determined the 50% plaque reduction neutralization test (PRNT50) and PRNT90 antibody titres to BA.2 virus in sera (twenty each collected 3-5 weeks after third dose) from cohorts vaccinated with three doses of BNT162b2, three doses of CoronaVac, two doses of CoronaVac followed by a third dose of BNT162b2 and those convalescent from SARS-CoV-2 (ancestral virus) (143-196 days after infection). We compared the PRNT titres to BA.2 with titres to BA.1 and ancestral virus. We demonstrate that PRNT50 and PRNT90 antibody titres to BA.2 are markedly reduced compared with those to ancestral virus and reduced as much as was observed for BA.1 virus. Those vaccinated with three doses of BNT162b2 or vaccinated with two doses of CoronaVac and a third dose of BNT162b2 develop PRNT antibody titres above the protective threshold from symptomatic infection. Those vaccinated with three doses of CoronaVac fail to achieve protective levels of PRNT50 antibody to BA.2 subvariant of Omicron 3-5 weeks after vaccination.