Post-COVID-19 Vaccination Infection Among Adults in Saudi Arabia: A Cross-Sectional Study

Background: While vaccines were one of the most effective tools to combat the COVID-19 pandemic, breakthrough infections have been reported.

Aim of the work: We aim to evaluate the effectiveness of Pfizer and AstraZeneca vaccines in preventing breakthrough infection, as well as to determine the possible risk factors and outcomes of post-vaccination infection.

Methods: This is a cross-sectional study using self-reported data of adult Saudi residents, including Saudi and non-Saudi people who received at least two doses of either Pfizer or AstraZeneca vaccines. Based on the presence of COVID-19 symptoms that were confirmed by PCR, the participants were classified into three groups: (1) those with evidence of infection before vaccination, (2) those who had infection after vaccination, and (3) those who had infection before and after vaccination. For further evaluation, we compared the severity and outcomes in the participants who were infected before and after vaccination.

Results: The study included 694 participants: 69.1% received three doses of the vaccine, and 71.1% of them were vaccinated with the Pfizer vaccine. COVID-19 infection was reported in 48.3% of the total subjects, with a higher infection rate (17.8%) after vaccination compared to 12.5% before vaccination. Additionally, 18.32% of participants experienced infection both before and after vaccination. Out of the total 694 participants, 137 (19.7%) had breakthrough infections. Pfizer vaccine was more prevalent among the non-infected group (74.25% vs. 65.5%), while AstraZeneca vaccine was more prevalent among the infected group (6.4% vs. 5.9% (p<0.039). Diabetes was significantly higher among the infected group (16.9% vs. 8.1%, p=0.001, OR=2.29, 95% CI=1.42-3.68). Among those who were infected before and after vaccination, 71.9% reported less severe symptoms after vaccination.

Conclusion: Breakthrough infections may occur after vaccination; however, vaccines are overall effective in preventing severe symptoms. Pfizer vaccine appeared to be more effective in preventing COVID-19 infection. The presence of comorbidities, including diabetes, may increase the risk of infection.