Introduction: Covishield^® (a recombinant, replication-deficient chimpanzee adenovirus vaccine) produces neutralizing antibodies against COVID-19. We aimed to compare the serum anti-spike (S) IgG antibodies between patients with recent breakthrough COVID-19 and recent COVID-19 in unvaccinated. Methodology: We prospectively recruited 60 consecutive adult patients (age 36.8±9.7 years) with and without recent (28-60 days before enrollment) COVID-19 infections. We categorized them into three groups: breakthrough infection (Group I; n=31); vaccinated and without recent COVID-19 (Group II;n=9); and recent COVID-19 in unvaccinated (Group III; n=20). The serum antibody titer was measured in duplicate by EUROIMMUN® Anti-SARS-CoV-2 ELISA kits. Results: All vaccinated received two doses of Covishield^®. Only 5 patients required oxygen during recent COVID-19 infections. Antibody titers were measured 35.1±3.6 days after the recent infection. The antibody titer between men and women was not different. Group I had a significantly higher antibody titer (9.73±1.14) than Group II (8.28±1.27; p<0.01) and Group III (4.63±3.68; p<0.001). The median interval between the last dose of the vaccine and the breakthrough infection was 290 days. The antibody titer and the interval between the recent COVID-19 infection and the estimation of antibodies showed no association. The waning of immunity following vaccination is likely to be the reason for the lower antibody titer in Group I than in Group II. Conclusions: Covishield^® vaccination produces higher antibody titers compared to natural infection. The breakthrough infection in previously vaccinated augments antibody titer.