Antibody response to variants during Omicron outbreak after BNT162b2 booster in Korean healthcare workers

Abstract In South Korea, the booster shot for COVID-19 was carried out amid concerns about the effectiveness of the existing vaccine. The virus neutralization test (sVNT) inhibition (%) score for the wild-type and delta variant significantly and uniformly increased (97%, 98%; p < 0.001) but it was decreased for the omicron after the BNT162b2 booster dose (75%; p < 0.001). In 41 HCWs (39.0%), infected with the omicron, no difference in immunogenicity, adverse events, and effectiveness between homogeneous and heterogeneous boosters were observed. In cohort 2, 58 HCWs included, at the fourth month of the booster dose, sVNT inhibition to omicron was significantly increased in the omicron-infected group (95.13%) compared to the non-omicron-infected (mean of 48.44%; p < 0.001). It is difficult to respond to the current vaccines to the Omicron variant adequately. Developing a variant-response vaccine should be prioritized, especially for the additional vaccination for HCW or previously infected persons.