Background: The emergence of new
COVID-19 variants of concern coupled with a global inequity in
vaccine access and distribution has prompted many public health authorities to circumvent the
vaccine shortages by altering vaccination protocols and prioritizing persons at high risk. Individuals with previous
COVID-19 infection may not have been prioritized due to existing humoral immunity. Objective: We aimed to study the association between previous
COVID-19 infection and antibody levels after
COVID-19 vaccination. Methods: A serological analysis to measure SARS-CoV-2
immunoglobulin (Ig)G,
IgA, and
neutralizing antibodies was performed on individuals who received one or two doses of either
BNT162b2 or ChAdOx1
vaccines in Kuwait. A Student t-test was performed and followed by generalized linear regression models adjusted for individual characteristics and comorbidities were fitted to compare the average levels of
IgG and
neutralizing antibodies between vaccinated individuals with and without previous
COVID-19 infection. Results: A total of 1,025 individuals were recruited. The mean levels of
IgG,
IgA, and
neutralizing antibodies were higher in vaccinated subjects with previous
COVID-19 infections than in those without previous
infection. Regression analysis showed a steeper slope of decline for
IgG and
neutralizing antibodies in vaccinated individuals without previous
COVID-19 infection compared to those with previous
COVID-19 infection. Conclusion: Previous
COVID-19 infection appeared to elicit robust and sustained levels of SARS-CoV-2
antibodies in vaccinated individuals. Given the inconsistent supply of
COVID-19 vaccines in many countries due to inequities in global distribution, our results suggest that even greater efforts should be made to vaccinate more people, especially individuals without previous
COVID-19 infection.