COVID-19 vaccination reduced the severity of the Omicron-driven pandemic wave in Saudi Arabia

By Neha MathurReviewed by Aimee MolineuxOct 14 2022

In a recent study published in the Journal of Infection and Public Health, researchers conducted a retrospective study of all coronavirus disease 2019 (COVID-19) cases from a single hospital in the Kingdom of Saudi Arabia (KSA) between December 25, 2021, and February 30, 2022.

They described the epidemiology and clinical characteristics of COVID-19 patients during the third pandemic wave when the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant was predominant.

Background

The KSA had managed to control the spread of SARS-CoV-2 within the country to a large extent through widespread vaccination programs. With the emergence of Omicron, the daily reported cases in the KSA surged to 4000/day from less than 100/day in the preceding months.

Although compared to Delta, Omicron caused less severe infections, fewer hospitalizations, intensive care unit (ICU) admissions, and much-reduced mortality, there was an urgent need to evaluate its effects in the general population.

About the study

In the present study, researchers reviewed all COVID-19 cases from a single medical center in KSA and gathered data to study the characteristics of patients during the Omicron wave. This data encompassed their demographics, clinical symptoms, pre-existing medical conditions, COVID-19 vaccination status, date of last vaccination, and SARS-CoV-2 infection. Further, the researchers assessed whether or not these COVID-19 patients required hospital or ICU admission.

For statistical analyses, they first summarized data as numbers and percentages. They compared categorical data using a chi-square test, including admitted and non-admitted patients and gender-based data with other covariates.

A binary logistic regression analysis helped the researchers model multiple covariates with admission status and gender. Furthermore, they constructed a Boxplot of the cycle threshold (CT) values of SARS-CoV-2 reverse transcriptase-polymerase chain reaction (RT-PCR) with COVID-19 vaccine doses. Finally, the team used Kaplan-Meier curve analysis to determine the days from the last COVID-19 vaccine to the subsequent occurrence of SARS-CoV-2 infection.

Study findings

The final study analysis covered 400 Omicron-infected patients, of which 55% were males, and the remaining were females. The most common pre-existing medical conditions were diabetes mellitus and hypertension, 10.5% and 7.5%. The most striking feature of the Omicron wave was the significantly lower hospitalization rate (only 14%) compared to prior pandemic waves. Only 3.5% and 2% of 400 Omicron-infected patients required ICU admission and mechanical ventilation, respectively.

Further, it was inversely related to the number of COVID-19 vaccine doses. In a binary logistic analysis, while hospital admission was significantly associated with headache and sore throat, fever and diabetes mellitus were inversely associated with hospital admission.

The most common symptoms observed in the study of patients infected with Omicron were sore throat, cough, fever, and headache, observed in 39.8%, 39.5%, 33%, and 30.5% of patients, respectively. The clinical presentation and comorbidities did not change with the patient's gender during the Omicron-driven pandemic wave. However, the occurrence of sore throat in a binary logistic regression showed a higher rate among males with an OR of 2.014.

Regardless of the vaccination status, more Omicron-infected than Delta-infected patients experienced sore throats (70.5% vs. 60.8%). Intriguingly, these patients also had odynophagia; however, anosmia, a pathognomonic symptom of previous SARS-CoV-2 variants, was markedly low in Omicron-infected patients.

Across male and female patients, the average time to SARS-CoV-2 infection from the last vaccination was 131.60 days. The average CT value was higher in the recipients of two or three vaccine doses than the recipient of one dose of the COVID-19 vaccine; however, this difference did not reach a statistical difference.

The observed differences during different COVID-19 pandemic waves likely reflected differences in the study population or the interaction between the factors and the vaccination.

Conclusions

The current study remarkably depicted the epidemiological and clinical characteristics of COVID-19 patients during the Omicron wave in KSA. They had a milder disease and required less hospitalization and less ICU admission. Since most patients had received COVID-19 vaccines, it showed the importance of COVID-19 vaccination in limiting disease severity and decreasing the need for hospitalization.