Effect of Homologous and Heterologous Booster in COVID-19 Vaccination

Abstract

Background: COVID-19 became a global health crisis in early 2020, and the way out of the crisis was the rapid development of vaccines by Sinopharm, Pfizer, and Sputnik, among others, which played a crucial role in controlling the pandemic. Therefore, this study aims to investigate the long-term immune response by measuring the levels of anti-S1 IgG antibodies induced by homologous and heterologous vaccination regimens. Methods: We investigated the titer of the anti-S1 IgG antibody produced for the viral surface antigen 3, 6 months after the second dose, before the third dose, and 1, 3, and 6 months after the third dose. Results: Anti-S1 IgG antibody levels significantly increased three/six months after the second dose and following the booster in individuals without prior COVID-19 infection who received all three homologous vaccine doses. The group that initially responded poorly to Sinopharm showed a significant and sustained increase after receiving the Pfizer booster. Additionally, prior SARS-CoV-2 infection between primary and booster vaccination boosted anti-S1 antibody titers in all individuals, regardless of the vaccine used. The highest vaccine efficacy was observed during the primary vaccination period and declined over time, especially during the omicron-dominant period. Conclusions: The results suggest that while homologous and heterologous booster doses can significantly enhance anti-S1 IgG antibody levels, prior SARS-CoV-2 infection and the type of vaccine administered influence the duration and magnitude of the immune response.

Keywords: COVID-19; Pfizer; Sinopharm; Sputnik vaccine; anti-S1 IgG antibodies.

Figure 1

Marker of humoral immune response, anti-S1 IgG antibodies, after vaccination with (A) three (I–III) doses of Pfizer; (B) three (I–III) doses of Sinopharm; (C) all three (I–III) doses of Sputnik vaccine; and (D) a combination of Sinopharm and Pfizer vaccines (two doses of Sinopharm and third dose of Pfizer, SSP) in individuals with no history of COVID-19. * p < 0.05; *** p < 0.001.

Figure 2

Marker of humoral immune response, anti-S1 IgG antibodies, after vaccination with (A) three (I–III) doses of Pfizer; (B) all three (I–III) doses of Sinopharm; (C) three (I–III) doses of Sputnik vaccine; and (D) a combination Sinopharm and Pfizer vaccines (two doses of Sinopharm and third dose of Pfizer, SSP) in individuals with a history of COVID-19.

Figure 3

Comparison of different vaccines in time points 3 and 6 months after the second (II) dose; before the third (III) dose; and 1, 3, and 6 months after the third dose. Marker of humoral immune response, anti-S1 IgG antibody, during vaccination with all three doses of Pfizer (PPP); all three doses of Sinopharm (SSS); all three doses of Sputnik vaccine (SpSpSp) and a combination of Sinopharm and Pfizer vaccine (two doses of Sinopharm and third dose of Pfizer, SSP) in individuals without (A) and with (B) a history of COVID-19. * p < 0.05; *** p < 0.001.There were no differences among measured time points between groups in subjects with COVID-19 (ANOVA showed no statistical significance among groups) (Figure 3B). In addition, subjects who had COVID-19 had higher baseline values 3 months after the second dose in all groups studied, but again without statistical significance. However, subjects who had received three doses of the Sinopharm vaccine and had a history of COVID-19 had higher antibodies one month after the third dose (p < 0.05). However, the situation reversed after 6 months (Figure 4). In addition, the history of COVID-19 had prolonged the immune response in the SSP group up to 3 months after the second dose (p < 0.05), a difference that was similar before the third dose (p < 0.001).

Figure 4

Comparison of anti-S1 IgG antibody levels in individuals with history/no/of COVID-19 in different time points 3 and 6 months after the second (II) dose; before the third (III) dose; and 1, 3 and 6 months after the third dose during vaccination with all three doses of Pfizer (PPP) (A); all three doses of Sinopharm (SSS) (B); all three doses of Sputnik vaccine (SpSpSp) (C); and a combination of the Sinopharm and Pfizer vaccine (two doses of Sinopharm and third dose of Pfizer, SSP) (D). * p < 0.05; *** p < 0.001.