Antibody Response after a Booster COVID-19 Vaccine Mixing in Vietnam

Background: The booster vaccine is essential for maintaining the antibody against the severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) virus. This study sought to evaluate the antibody response after booster coronavirus disease 2019 (COVID-19) vaccines and compare the immunogenic by different vaccine combination strategies. Methods: A cross-sectional study in Hanoi, Vietnam was conducted on 679 adult participants who received two doses of vaccines with any combination of AstraZeneca, Pfizer, and Moderna during the COVID-19 vaccination campaign in 2021. The SARS-CoV-2 S1/S2 Immunoglobulin G (IgG) antibody concentrations were measured by the LIAISON SARS-CoV-2 S1/S2 IgG and presented as arbitrary units. Results: We found that the median (interquartile range (IQR)) of IgG level among those who completed two doses of Moderna and Pfizer was 484.55 (284.80) AU/mL and 349.00 (362.50) AU/mL, respectively. Meanwhile, the counterpart of AstraZeneca was 110.00 (128.10) AU/mL. Mixing two doses of AstraZeneca-Pfizer has higher odds of having high IgG level than two doses of Pfizer (Odds Ratios (OR) = 2.94, 95% Confidence Intervals (CI): 1.57-5.51), AstraZeneca (OR = 28.50, 95% CI: 15.00-54.14). Conclusions: We found that the matching two doses of mRNA vaccines are more immunogenic as compared to the DNA vector vaccines. Furthermore, mixing AstraZeneca-Pfizer has higher antibody quantities as compared to matching vaccines, while lower the rate of advert events.