Comparative Study about the Effectiveness of Certain Vaccines Against SARS-CoV-2 Reinfection among Iraqi Population

Background: With the continuation of the COVID-19 pandemic, some COVID-19 patients have a risk of SARS-CoV-2 reinfection. Viral gene sequencing has found that some of these patients were reinfected by a different and others by the same strains. This has raised concerns about the effectiveness of immunity after infection and the reliability of vaccination. We conducted a survey study to assess the characteristics of patients with reinfection and possible causes .Methods and Results: An online survey study was conducted in October 2021 on Facebook social media. This study included 2413 respondents: 1315 subjects received the BNT162b2 mRNA-based Vaccine (Pfizer/BioNTech), 811 received the ChAdOx1 (AZD1222) adenoviral vector vaccine (Oxford-AstraZeneca), and 287 received the Sinopharm inactivated COVID-10 vaccine (BBIBP-CorV). The Pfizer/BioNTech vaccine appeared to be the most effective (84%) in preventing reinfection compared to the Oxford-AstraZeneca vaccine (79%) and the Sinopharm vaccine (70%) (P<0.0001). The reinfection after the first dose appeared to be proximate between the Pfizer/BioNTech vaccine and the Oxford-AstraZeneca vaccine: 10% and 11%, respectively, while the reinfection after the first dose of the Sinopharm vaccine was highest (18%) (P=0.0005). The reinfection after full dose vaccination appeared to be very low in the Pfizer vaccine (6%) but higher in the Astra Zeneca vaccine (10%), which was proximate to the reinfection after the Sinopharm vaccine (12%) (P=0.000). In addition, subjects with comorbidities had three times the risk of reinfection than those without. Conclusion: Vaccinated patients can be reinfected by SARS-CoV-2, with reinfection rates depending on the vaccine type and comorbidities.