SARS-CoV-2 IgG Antibody Response after Immunization of Healthcare Workers with Inactivated COVID-19 Vaccine (CoronaVac) at Phyathai 3 Hospital

OBJECTIVES: To evaluate the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) anti-spike Immunoglobulin G (IgG) antibody response after CoronoVac immunization of healthcare workers at Phyathai 3 Hospital. MATERIALS AND METHODS: The descriptive study was performed at Phyathai 3 Hospital between March 2021 and May 2021. Healthcare workers who received two doses (three weeks apart) of the CoronaVac vaccine were included. Blood samples for anti-spike IgG antibodies were taken from each healthcare worker before getting vaccinated and four weeks after completing two doses of the vaccine. RESULT: A total of 88 healthcare workers were enrolled in our study. Fifty-three (60%) of them were female, 84(95%) were physicians, 46(52%) were obese and 33(37.5%) had at least one coexisting condition. The mean age was 45.8 ± 9.3 years. Seven (8%) of participants were older than 60 years of age. All participants did not have IgG antibodies at baseline. Eighty-seven (98.9%) healthcare workers had seroconversion of anti-spike IgG antibodies four weeks after completing two doses of the CoronaVac vaccine. The mean level of anti-spike IgG at four weeks after completing vaccination was 115+/-85 unit/ml (range, 1.77-297.3 unit/ml). Anti-spike IgG levels were significantly higher in females than males ( p = 0.02). Normal-weight participants showed higher anti-spike IgG levels than obese individuals ( p = 0.01). IgG antibody responses tended to decrease with age. The highest IgG levels were observed in the ages of 30-40 years. CONCLUSION: Two doses of the CoronaVac vaccine could induce a 98.9% rate of seroconversion in healthcare workers. Female and normal-weight participants were significantly associated with a higher level of IgG response. Younger adults had a higher immune response than older adults in our setting.