Breakthrough Infection Influenced SARS-CoV-2 IgG Antibody Titer in a Group of Healthcare Providers

Background: The phenomenon of breakthrough infection during the COVID-19 pandemic has raised concerns regarding the efficacy of the vaccinations and healthcare providers are exposed to instances on a regular basis for professional reasons, putting them at risk. This study was aimed to look into the SARS-CoV-2 IgG status among the healthcare providers, reported with breakthrough infections. Methods: The study involved 78 healthcare providers (e.g., doctors, nurses, Lab personnel, support staffs) from a tertiary care hospital in Dhaka city. Blood samples were collected from participants who had received at least one dose of a COVID-19 vaccine, regardless of the incidence of breakthrough infection. SARS-CoV-2 IgG antibody level was estimated using an Enzyme-Linked Immunosorbent Assay (ELISA). Result: Out of the 78 participants, 31 had experienced breakthrough infection. The mean (±SD) SARS-CoV-2 specific IgG antibody level was 13.42±10.68×104 BAU/ mL. SARS-CoV-2 IgG antibody levels of the infected subjects were significantly higher than those without breakthrough infections (p=0.024). The highest IgG levels was observed in participants who received three vaccine doses (15.71±11.36×104 BAU/mL), followed by two doses (9.48±8.09×104 BAU/mL) and one dose (5.91±2.27×104 BAU/mL). Participants who experienced breakthrough infections after receiving the third dose demonstrated significantly higher IgG levels (p=0.035). Conclusion: Healthcare providers studied demonstrated substantial number of participants developing breakthrough infection and those had significantly higher level of endpoint SARS-CoV-2 IgG antibody. A dose dependent antibody response following vaccination could not be excluded.