Comparison of the reactogenicity and immunogenicity of a reduced and standard booster dose of the mRNA COVID-19 vaccine in healthy adults after two doses of inactivated vaccine.

ABSTRACT

The coronavirus disease 2019 (COVID-19) pandemic has been a serious healthcare problem worldwide since December 2019. The third dose of heterologous vaccine was recently approved by World Health Organization. The present study compared the reactogenicity and immunogenicity of the reduced and standard third booster dose of the BNT162b2 and mRNA-1273 vaccine in adults who previously received the two-dose CoronaVac vaccine. Results showed that headache, joint pain, and diarrhea were more frequent in the 15 g-than the 30 g-BNT162b2 groups, whereas joint pain and chilling were more frequent in the 100 g-than the 50 g-mRNA-1273 groups. No significant differences in immunogenicity were detected. These findings demonstrate that the reduced dose of the mRNA vaccines elicited antibody responses against the SARS-CoV-2 delta and omicron variants that were comparable to the standard dose. The reduced dose could be used to increase vaccine coverage in situations of limited global vaccine supply. HighlightsO_LIThe 15 g- and 30 g-BNT162b2, and 50 g- and 100 g-mRNA-1273 booster doses were compared C_LIO_LIBooster vaccination with the mRNA vaccine elicits high Ig and IgG anti-RBD in CoronaVac-vaccinated adults C_LIO_LINo differences were observed in antibody responses after the reduced or standard booster dose of the mRNA vaccine in CoronaVac-vaccinated adults C_LIO_LINeutralizing antibodies against the delta and omicron variants were significantly higher after the booster dose C_LIO_LINeutralizing antibody titers were lower against the omicron variant than the delta variant in all vaccinated adults C_LI