Association of COVID-19 vaccines and antibody response in individuals with prior Coronavirus infection

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) was one of the worst pandemics and viral infections affecting humans across the globe. Many non-pharmaceutical and pharmacological interventions were initiated to prevent the spread of infection and control the disease transmission. Covishield and Covaxin were among the most common vaccines given in India to control the spread of the coronavirus and its variants among the public. To evaluate the efficacy of COVID-19 vaccines in increasing serum and salivary IgA antibody levels and how they are correlated to patients' demographics, medical conditions, and previous history of coronavirus infection in the Udupi district, Karnataka, India. 127 participants who received two doses of the COVID-19 vaccine were recruited. Anti-SARS-CoV-2 IgA antibodies specific to COVID-19 in serum and saliva were measured by ELISA. The mean serum IgA levels were compared at 0-6 months, 6-12 months, and > 12 months. The IgA levels were compared with age, gender, history of COVID-19 infection, timing of vaccination, body mass index, and comorbidities. The mean serum IgA levels in individuals with a history of COVID-19 (12.59 ± 5.67 μg/ml) were higher than those without a history of infection (8.5 ± 7.20 μg/ml). Among those with a history of COVID-19 infection, 8.1% were infected before the vaccination, and 91.9% were infected post-vaccination. Serum IgA levels were lower in participants under 30 years of age (5.27 ± 3.14 μg/mL) compared to participants above 30 years of age (8.93 ± 4.56 μg/mL) (P = 0.001). Antibody levels were influenced by age, presence of comorbidities, and history of coronavirus infection. Individuals with prior COVID-19 infection showed higher serum IgA antibody levels. Serum and salivary IgA levels were even detected in a group of participants with more than 12 months post-vaccination period.