RESUMO
Inactivated SARS-CoV-2 vaccine (CoronaVac) is commonly used in national immunization programs. However, the immune response significantly declines within a few months. Our study assessed the immune response against SARS-CoV-2 after receiving booster shots of BNT162b2 or ChAdOx1 among health care workers who previously received CoronaVac as their primary immunization. Fifty-six participants who received ChAdOx1 and forty-two participants who received BNT162b2 were enrolled into this study, which evaluated immune responses, including anti-SARS-CoV-2 spike total antibodies (Elecsys®), surrogated viral neutralization test (sVNT) to ancestral strain (cPass™; GenScript), five variants of concern (Alpha, Beta, Gamma, Delta, and Omicron) (Luminex; multiplex sVNT) and the ELISpot with spike (S1 and S2) peptide pool against the ancestral SARS-CoV-2 strain. The samples were analyzed at baseline, 4, and 12 weeks after primary immunization, as well as 4 and 12 weeks after receiving the booster. This study showed a significant increase in anti-SARS-CoV-2 spike total antibodies, sVNT, and T-cell immune response after the booster, including against the Omicron variant. Immune responses rapidly decreased in the booster group at 12 weeks after booster but were still higher than post-primary vaccination. A fourth dose or a second booster should be recommended, particularly in health care workers.
RESUMO
BACKGROUND: Inactivated SARS-CoV-2 (CoronaVac®, Sinovac, or SV) and ChAdOx1 nCoV-19 (Vaxzevria®, Oxford-Astra Zeneca, or AZ) vaccines have been administered to the health care workers (HCWs). OBJECTIVE: To determine the short-term immune response after the SV and AZ vaccinations in HCWs. METHODS: In this prospective cohort study, HCWs who completed a 2-dose regimen of the SV or AZ were included. Immune response was evaluated by surrogate viral neutralization test (sVNT) and anti-SARS-CoV-2 total antibody. Blood samples were analyzed at 4 and 12 weeks after the complete vaccination. The primary outcome was the seroconversion rate at 4-weeks after complete immunization. RESULTS: Overall, 185 HCWs with a median (IQR) age of 40.5 (30.3-55.8) years (94 HCWs in the SV group and 91 in the AZ group) were included. At 4 weeks after completing the SV vaccination, 60.6% (95%CI: 50.0-70.6%) had seroconversion evaluated by sVNT (≥ 68% inhibition), comparable to the patients recovered from mild COVID-19 infection (69.0%), with a rapid reduction to 12.2% (95%CI: 6.3-20.8) at 12 weeks. In contrast, 85.7% (95%CI: 76.8-92.2%) HCWs who completed two doses of the AZ for 4 weeks had seroconversion, comparable to the COVID-19 pneumonia patients (92.5%), with a reduction to 39.2% (95%CI: 28.4-50.9%) at 12 weeks. When using the anti-SARS-CoV-2 total antibody level (≥ 132 U/ml) criteria, only 71.3% HCWs in the SV group had seroconversion, compared to 100% in the AZ group at 4 weeks. CONCLUSIONS: A rapid decline of short-term immune response in the HCWs after the SV vaccination indicates the need for a vaccine booster, particularly during the ongoing spreading of the SARS-CoV-2 variants of concern.
