This article was originally published here
Vaccine. April 13, 2022: S0264-410X(22)00438-8. doi: 10.1016/j.vaccine.2022.04.020. Online ahead of print.
BACKGROUND: CoronaVac was administered as the first COVID-19 vaccine for Thai healthcare workers (HCWs) in early 2021 in response to the outbreak of new variants. This study aimed to assess the dynamics of the humoral immune response as well as the short-term side effects resulting from the booster dose of BNT162b2 after completion of a double dose of CoronaVac in Thai healthcare workers.
METHODS: This study was conducted at a university hospital in northern Thailand in August and September 2021. Participants were 50 healthcare workers vaccinated with 2 doses of CoronaVac and were to receive a booster dose of BNT162b2. Anti-SARS-CoV-2 IgG antibody levels and short-term side effects were assessed. Anti-RBD level was determined using Architect SARS-CoV-2 IgG II Quant (Abbott).
RESULT: Of the 50 participants, 37 were women. The median age was 33.0 years. The mean time between the second CoronaVac shot and the BNT162b2 booster shot was 81.7 days (SD = 25.0). The median anti-SARS-CoV-2 IgG antibody level on the date of the booster vaccination, as well as on day 14 and day 28 after the booster was 335.5 AU/ml, 31,613.5 AU/ ml and 20,311.9 AU/ml, respectively. Fourteen days after the booster, 94% of participants had anti-SARS-CoV-2 IgG antibody levels above 50.0 AU/ml. Being a woman, more logarithmic anti-SARS-CoV-2 IgG antibodies before the booster vaccination and a longer interval between the second injection and the booster injection were found to be significantly associated with higher levels of IgG antibodies anti-SARS-CoV-2 at days 14 and 28 post-booster. No serious adverse events were reported.
CONCLUSION: A booster dose of BNT162B2 promoted a high level of anti-SARS-CoV-2 IgG antibodies among healthcare workers who received 2 doses of CoronaVac. The time between the second shot of CoronaVac and the booster shot should be at least three months. No serious adverse effects were observed.