Publication date: Aug 01, 2023
Immunity against SARS-CoV-2 infection in vaccinated individuals varies based on the vaccine type, duration after vaccination or infection, and SARS-CoV-2 variant type. We conducted a prospective observational study to evaluate the immunogenicity of a booster vaccination with AZD1222 after two doses of CoronaVac (booster group) compared to individuals who had SARS-CoV-2 infection after receiving two doses of CoronaVac (infection group). We used a surrogate virus neutralization test (sVNT) to evaluate immunity against wild-type and Omicron variant (BA. 1) at 3 and 6 months after infection or booster dose. Of the 89 participants, 41 were in the infection group, and 48 were in the booster group. At 3 months post-infection or booster vaccination, the median (IQR) sVNT against wild-type was 97. 87 % (97. 57-97. 93 %) and 97. 65 % (95. 38-98. 00 %), p = 0. 66, respectively, while the sVNT against Omicron was 18. 8 % (0-47. 10 %) and 24. 46 (11. 69-35. 47 %), p = 0. 72 respectively. At 6 months, the median (IQR) sVNT against wild-type was 97. 68 % (95. 86-97. 92 %) in the infection group, higher than 94. 7 % (95. 38-98. 00 %) in the booster group (p = 0. 03). Results showed no significant difference in immunity against wild-type and Omicron at 3 months between the two groups. However, the infection group exhibited better immunity than the booster group at 6 months.
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