Demographic Characteristics and Status of Vaccinated Individuals with a History of COVID-19 Infection Pre- or Post-Vaccination: A Descriptive Study of a Nationally Representative Sample in Saudi Arabia

Background: Saudi Arabia expedited the approval of some COVID-19 vaccines and launched mass vaccination campaigns. The aim of this study was to describe the demographics of vaccinated COVID-19 cases and compare the mortality rates of COVID-19 cases who were infected post-vaccination in Saudi Arabia.

Methods: This was a retrospective cohort study. We retrieved data for COVID-19 cases who were infected pre- or post-vaccination and had received at least one injection of the Oxford-AstraZeneca or Pfizer-BioNTech vaccine from 4 December 2020 to 15 October 2021.

Results: The number of patients who were infected and had received at least one dose of a COVID-19 vaccine was 281,744. Approximately 45% of subjects were infected post-vaccination, and 75% of subjects had received the Pfizer-BioNTech vaccine. Only 0.342% of the patients who were infected post-vaccination died, and 447 patients were admitted to ICUs. Most of the patients who were infected with COVID-19 post-vaccination and were admitted to ICUs (69.84%) had received only one dose of the vaccine (p < 0.0001). The mean time to infection for patients who had received one and two doses of the Oxford-AstraZeneca vaccine were 27 and 8 days longer than their counterparts who had received one and two doses of Pfizer-BioNTech vaccine, respectively. No difference in the odds of mortality between the Pfizer-BioNTech and Oxford-AstraZeneca vaccines was found (OR = 1.121, 95% CI = [0.907-1.386], p-value = 0.291). Patients who had received two doses of the vaccine had significantly lower odds of mortality compared to those who had received one dose (p < 0.0001).

Conclusions: Vaccines are vital in combating the COVID-19 pandemic. The results of this study show no difference between the Pfizer-BioNTech and Oxford-AstraZeneca vaccines in the rate of mortality. However, the number of vaccine doses was significantly associated with a lower risk of mortality. Future studies should examine the effectiveness of different COVID-19 vaccines using real-world data and more robust designs.