Antibody responses in omicron BF.7-infected patients vaccinated with inactivated SARS-CoV-2

Objective: Our study aimed to investigate antibody responses in omicron BF.7-infected patients after being vaccinated with inactivated SARS-CoV-2.

Methods: Blood serum samples were collected every 2-7 d, 1 w before infection, during the acute infection period and recovery period, and every month after recovery to detect IgG, IgM, IgA, neutralizing antibodies, and neutralizing antibodies against different omicrons in the acute phase.

Results: The levels of IgG, IgA and neutralizing antibodies increased sharply at 6-7 d after infection, and the levels of IgG and neutralizing antibodies peaked rapidly within 1-2 w, lasting for 3-4 w, and the antibody levels gradually decreased at 4-8 w after infection. The level of neutralizing antibodies against the wild-type strain SARS-CoV-2 was much greater than that against the variant strains during the acute infection period.

Conclusion: After being infected with omicron BF.7, the IgG and neutralizing antibodies in inactivated SARS-CoV-2-vaccinated individuals increase sharply 6-7 days after infection, which is earlier than those in the initial WT SARS-CoV-2 infection, and the peak time within 1-2 w is shorter. The levels of IgG, neutralizing antibody, and IgA antibodies are high, and the levels of IgM antibodies are low; however, the neutralizing antibodies are mainly against the wild-type strain of SARS-CoV-2.