Short-Term Change in IgG Antibody Elicited by Omicron BA.5 Infection and Inhaled Ad5-nCoV Vaccine Among Healthcare...

Little is known about the immune response induced by the SARS-CoV-2 Omicron BA.5 variants or the inhaled adenovirus vector vaccine. In this study, we investigated the short-term profile of antireceptor-binding-domain IgG antibody responses elicited by either the virus or the vaccine.

A cohort of healthcare workers who were infected with Omicron BA.5 or who received the inhaled adenovirus vector vaccine was identified between August and December 2022. Blood samples were collected twice to detect IgG antibodies against the receptor-binding domain of the SARS-CoV-2 spike protein. Baseline characteristics were obtained through questionnaires. Multivariate linear mixed-effect models were applied to assess the changes in IgG antibody levels between the two laboratory test time points, adjusting for baseline covariates.

Among 1146 identified healthcare workers, a total of 419 healthcare workers with known infection status who provided informed consent were eligible for inclusion in the study. The study participants were mostly female (71.8%), had received three doses of intramuscularly injected inactivated vaccine before follow-up (93.8%), and had no comorbidities (94.3%). We estimated that the IgG level increased by 5.1% per week over the 2 months following Omicron BA.5 infection. No significant change in IgG antibody levels in the short term was observed within 1 month after receiving the inhaled adenovirus vector vaccine.

These findings suggested that the inhaled adenovirus vector vaccine may provide modest protection against Omicron BA.5 infection in the healthcare worker population.