The Effect of COVID-19 Vaccines on Hospital Admission and Severity of Symptoms Among COVID-19 Patients in Saudi Arabia, 2021.

Introduction Following the World Health Organization (WHO) declaration of coronavirus disease 2019 (COVID-19) as a pandemic, Saudi Arabia took unpreceded precautions to prevent and control the spread of the severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) infection. It is one of the first countries in the world to grant the authorization to use the Pfizer-BioNTech vaccine. This study aimed to assess the effect of one dose of COVID-19 vaccines (Pfizer-BioNTech, Manhattan, New York City and Oxford-AstraZeneca, Cambridge, United Kingdom) among the Saudi population regarding symptom severity, hospital admission rate, and death. Methods An observational retrospective cohort study was conducted using data from COVID-19 surveillance records at King Abdulaziz Medical City (KAMC), Saudi Arabia, from January to May 2021. All confirmed COVID-19 patients who had positive tests by reverse transcription polymerase chain reaction (RT-PCR) assay of a nasopharyngeal swab were included in the study. Patients diagnosed outside KAMC and cases below 18 years old were excluded from the study. The research was approved by King Abdullah International Medical Research Center (NRJ21J/303/12). Multivariable logistic regression was conducted to estimate the odds of hospitalization among vaccinated and unvaccinated patients. Results A total of 1058 cases were included in the analysis. Two hundred sixty-five (265; 25%) patients were vaccinated with one dose of either Pfizer-BioNTech or Oxford Astra-Zeneca, and 793 (75%) were unvaccinated. The median age was 34 (IQR 25-51), primarily Saudi (94.6%) and male (59.5%). The odds of being vaccinated (CI: 1.284-2.882, P 0.002) were 1.924 times greater for males than females. Young patients below 40 had 1.997 times higher odds (CI: 1.238-3.222, P 0.004) of being vaccinated than patients above 60. The hospital admission rate was low among both groups (12.9%); however, it was significantly lower among the vaccinated group (2.3%) as compared to the unvaccinated (16.5%). The results showed significant differences in symptom severity among the groups. For vaccinated, only one patient (0.4%) died, one patient was admitted to the ICU, and one patient (0.4%) was admitted to the hospital isolation ward. On the contrary, among the unvaccinated group, 19 patients (2.4%) died, 17 patients (2.1%) were admitted to the ICU, and 114 patients (14.4%) were admitted to the hospital isolation ward. Conclusion This study demonstrates that one dose of COVID-19 vaccines, either Pfizer-BioNTech or Oxford-AstraZeneca, reduced the probability of death by 2% and hospital admission by 15% before the spread of the Delta variant (B.1.617). For generalizable results, nationwide studies using national surveillance data are recommended to assess multiple doses efficacy on different variants of the SARS-CoV-2 infection.