1973. The Antibody Neutralization Level after a BNT162b2 Vaccine Booster in Korean Healthcare Workers

Abstract Background We compared neutralizing antibodies in healthy healthcare workers against two different coronavirus 2019 disease (Covid-19) vaccines, a messenger RNA (mRNA)-based vaccine (BNT162b2) and a genetically modified organism (virus vector) vaccine (ChAdOx1), to obtain immunity. In our cohort, we tried to compare the level of neutralizing antibody production after a BNT162b2 vaccine booster and to analyze the level of neutralizing antibody titers for delta and omicron variant. Methods On November 23 to 25, 2021 and December 23 to 24, 2021, a total of 2,133 HCWs at Soonchunhyang University Bucheon Hospital had been vaccinated with BNT162b2 (Pfizer-BioNTech). Among the 115 HCWs who participated in the preceding study, all participants had no history of Covid-19 infection or suspected symptoms at the time of registration. We collected blood samples from participants four weeks after a third dose. All blood samples were analyzed using the commercial virus neutralization test kit (Genscript Biotech Corporation, Piscataway, NJ, USA). Results Titers were measured 2 months after the initial vaccination and before the booster of the BNT162b2 vaccine (i.e. 6 months after the initial vaccination), and 4 weeks after the booster. Neutralizing antibody level measured by percentage inhibition of surrogate virus neutralization test (sVNT) readings at negative control (unvaccinated) and 4 weeks after booster vaccination. BNT/BNT/BNT group was defined as a booster dose with BNT162b2 (Pfizer) after two doses of BNT162b2 vaccine (Pfizer) 3 weeks apart. ChA/ChA/BNT group was defined as a booster dose with BNT162b2 (Pfizer) after two doses of ChAdOx1 vaccine (AstraZeneca/Oxford) 12 weeks apart. Conclusion We found that the neutralizing antibody levels against omicron variant were higher among those who received a booster dose of the BNT162b2 vaccine. Disclosures All Authors: No reported disclosures.