Significant increase in anti-SARS-CoV-2 antibodies after administration of heterologous mRNA-based vaccine booster in individuals receiving two doses of inactivated COVID-19 vaccine: A single-center study in healthcare workers in Jakarta, Indonesia

Background
Vaccine plays an important role in breaking SARS-CoV-2 transmission and accelerating the path to pandemic recovery. Currently, there is still limited data on heterologous COVID-19 booster vaccination efficacy and effectiveness in Indonesia.
Methods
Antibody response was retrospectively analyzed from 156 serum collected from healthcare workers that have received mRNA-1273 vaccine as the booster against SARS-CoV-2. These individuals had previously received the full two doses of inactivated anti-SARS-CoV-2 vaccine. Serological analysis was performed to measure total antibody, as well as IgA and IgG antibodies specific to spike (S) protein using ECLIA and ELISA methods.
Results
A significant increase in total, IgA, and IgG antibody titers was reported in vaccine receiving a third heterologous booster dose of mRNA-based COVID-19 vaccine following two doses of inactivated type.
Conclusion
The third heterologous booster dose of vaccine may be beneficial to individuals with or without previous history of SARS-CoV-2 infection.