Objective: Various types and combinations of vaccines have been utilized at different time intervals due to the variable availability of vaccines in many countries during the Coronavirus Disease 2019 (COVID-19) pandemic. Most current vaccine administrations involve a series of primary doses followed by a homologous booster dose. This study aimed to examine the antibody levels after the BNT162b2 or CoronaVac vaccine was administered as a booster dose to volunteers who received two doses of CoronaVac and to identify the ideal vaccination combination.
Materials and Methods: This cross-sectional study included 254 participants. The groups consisted of volunteers who received two doses of CoronaVac, those who received two doses of BNT162b2, those who received two doses of CoronaVac plus one dose of BNT162b2, and finally, those who received three doses of CoronaVac. Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) specific spike (S) Immunoglobulin G (IgG) levels were measured by electrochemiluminescence method on Roche COBAS 8000 series using Anti-SARS-CoV-2 S kit.
Results: Antibody levels after three doses of CoronaVac were found to be lower compared to after two doses of CoronaVac + one dose BNT162b2 (p<0.001). IgG responses after three doses of the CoronaVac vaccine (two primary + one booster dose) were lower than those after two doses of BNT162b2 (p<0.001).
Conclusion: The use of a heterogeneous booster dose due to problems in vaccine supply may be a good alternative to the homologous approaches applied so far.