Study: Oral Nirmatrelvir and Severe Covid-19 Outcomes During the Omicron Surge. Image Credit: Cryptographer/Shutterstock

Efficacy of nirmatrelvirus therapy in preventing COVID-19 mortality and hospitalizations in high-risk patients during Omicron growth

At the end of 2021, there was a worldwide recovery of coronavirus disease 2019 (COVID-19) due to the occurrence of highly transmissible acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant Omicron. Omicron surpassed the Delta variant by the end of December 2021. At the beginning of January, Omicron spread considerably around the world, even in places with a high level of pre-existing immunity.

Study: Oral Nirmatrelvir and Severe Covid-19 Results during the Omicron Wave. Image credit: Cryptografer / Shutterstock


In December 2021, the Food and Drug Administration (FDA) granted an emergency use authorization (EUA) for the oral antiviral drug nirmatrelvir for the treatment of mild to moderate COVID-19 in patients at increased risk of developing a serious illness. A typical regimen for nirmatrelvir consists of five consecutive days of treatment after a positive diagnosis of COVID-19. The FDA EUA was based on a randomized, double-blind, placebo-controlled protease inhibition trial for COVID-19 in high-risk patients (EPIC-HR), which addressed nirmatrelvirus treatment in non-hospitalized, high-risk, symptomatic adults with COVID-19.

In a recent study published on Research Square* prepress server, researchers evaluated how effective nirmatrelvir is in preventing COVID-19-related deaths and hospitalizations in high-risk patients.

About the studio

The study used data from Clalit Health Services (CHS), a large medical facility that serves about half of Israel’s population, including nearly two-thirds of the elderly. The trial began on January 9, 2022 and ended on March 10, 2022, the first day that treatment was given to patients with kennels. Patients diagnosed with COVID-19 by February 24, 2022 were eligible.


A total of 109,213 individuals met the criteria for inclusion in the study. The mean age of study participants was 60 years, with 39% of participants. The most common comorbid conditions were obesity, diabetes and smoking. COVID-19 immunity was present in 78% of patients, acquired by either previous infection, vaccination, or hybrid immunity.

During the study period, 3,939 patients in the general population received at least one dose of nirmatrelvir. Participants aged 65 and over and those recently diagnosed with cancer had a significantly higher income. Participants without prior vaccination against COVID-19 and members of the Arab minority group had significantly reduced absorption.

The author presents the results for age groups over 65 and under 65 separately, because testing the interaction of nirmatrelvir with other variables showed significant differences by age groups.

COVID-19-related hospitalizations occurred in 343 of 1,435 treated patients and 334 of 64,959 untreated patients among 66,394 patients aged 40 to 64 years. COVID-19-related hospitalizations occurred in 776 of 42,8159 patients and more patients, 2,504 treated patients, and 762 of 40,315 untreated patients. Decreased immunity to COVID-19 and previous hospitalizations were the characteristics most significantly associated with a high incidence of COVID-19-related hospitalizations in both age groups. In the age range of 40-64 years, immunosuppression was strongly associated with hospitalizations.

COVID-19-related hospitalizations were reported in 182 of 20,531 patients with prior immunity and 161 of 45,863 patients with prior immunity in patients aged 40 to 64 years. COVID-19-related hospitalizations were reported in 273 of 3,306 patients with prior immunity and 503 patients with prior immunity and 39,513 patients with prior immunity among participants aged 65 and over.


During the increase in Omicron, nirmatrelvirus treatment was associated with a significant decrease in COVID-19 hospitalizations and mortality in people aged 65 and over. Although an observational study, the findings and apparent potential for major COVID-19 disease prevention could help decision-makers to allocate limited supplies to those for whom nirmatrelvir has proven successful.

* Important notice

Research Square publishes preliminary scientific reports that are not peer-reviewed and should therefore not be considered conclusive, leading clinical practice / health-related behavior, nor should it be treated as validated information.

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