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

In a recently published study in the Journal of Infection and Public Healthresearchers conducted a retrospective study of all cases of coronavirus disease 2019 (COVID-19) 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 features of COVID-19 patients during the third wave of the pandemic, when the omicron variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was prevalent.

background

The KSA had managed to largely contain the spread of SARS-CoV-2 within the country through widespread vaccination programs. With the advent of Omicron, daily reported cases in the KSA increased to 4000/day from less than 100/day in previous months.

Although Omicron caused fewer severe infections, fewer hospitalizations, intensive care unit (ICU) admissions, and greatly reduced mortality compared to Delta, there was an urgent need to assess its impact on the general population.

About the study

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

For statistical analysis, they first summarized the data in numbers and percentages. They compared categorical data using a chi-square test, including admitted and non-admitted patients, and sex-based data to other covariates.

Binary logistic regression analysis helped the researchers model multiple covariates with admission status and sex. In addition, they constructed a boxplot of SARS-CoV-2 reverse transcriptase polymerase chain reaction (RT-PCR) cycle thresholds (CT) with COVID-19 vaccine doses. Finally, the team used a Kaplan-Meier curve analysis to determine the days from the last COVID-19 vaccine to the subsequent emergence of SARS-CoV-2 infection.

study results

The final study analysis included 400 Omicron-infected patients, 55% of whom were men and the remainder were women. The most common pre-existing conditions were diabetes mellitus and high blood pressure, at 10.5% and 7.5%, respectively. The most striking feature of the Omicron wave was the significantly lower hospitalization rate (only 14%) compared to previous pandemic waves. Only 3.5% and 2% of 400 Omicron-infected patients required intensive care and mechanical ventilation, respectively.

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

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

More Omicron-infected than Delta-infected patients suffered from sore throat regardless of vaccination status (70.5% vs. 60.8%). Interestingly, these patients also had odynophagia; However, anosmia, a pathognomonic symptom of previous SARS-CoV-2 variants, was significantly low in Omicron-infected patients.

In male and female patients, the median time to SARS-CoV-2 infection since last vaccination was 131.60 days. The average CT value was higher in recipients of two or three doses of vaccine than in recipients of one dose of 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 vaccination.

Conclusions

The current study has remarkably illustrated the epidemiological and clinical characteristics of COVID-19 patients during the Omicron wave in KSA. They had milder disease and required fewer hospitalizations and fewer ICU admissions. Since most patients had received COVID-19 vaccines, the importance of COVID-19 vaccination in limiting disease severity and reducing the need for hospitalization was demonstrated.