Homologous or heterologous COVID-19 vaccine schemes: comparison of immune responses and side effects.

Real-life data are needed regarding the appropriate time and selection of vaccination strategies, homologous or heterologous. We aimed to compare neutralizing antibody levels and side effects in different vaccination schemes. The study included 310 Health Care Workers (HCWs) vaccinated with 5 different schemes. Antispike/RBD IgG levels were measured between 28 and 60 days after the last dose. Side effects in participants were recorded, and pharmacovigilance records were reviewed from the outpatient vaccine clinic. Mean age of the participants was 38 ± 11 years of whom 226 (72.9%) were female, and 84 (27.1%) were male. After booster doses, increasing antibody levels were detected in all groups. Mean antibody levels were detected to be statistically lower in 3 doses of inactivated vaccines group. The side effects were no significant difference between groups. Booster dose administration with mRNA vaccines stands out as the most accurate strategy for those at risk of contracting severe COVID-19 and HCWs caring for this population.