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

Efficacy of nirimatilvir treatment in preventing mortality and hospitalization due to COVID-19 in high-risk patients while increasing Omicron

In late 2021, there was a global resurgence of coronavirus disease 2019 (COVID-19) due to the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant Omicron. Omicron had overtaken the Delta variant by the end of December 2021. By early January, Omicron had spread widely throughout the world, even in places with high levels of pre-existing immunity.

Study: Oral Nirmatrelvir and severe Covid-19 outcomes while increasing Omicron. Image Credit: Cryptographer / Shutterstock


On December 22, 2021, the Food and Drug Administration (FDA) granted emergency use authorization (EUA) for the oral antiviral nirmatilvir to treat mild to moderate COVID-19 in patients at increased risk of developing severe disease. A typical nirmatelvir regimen consists of five consecutive days of treatment following a positive diagnosis of COVID-19. The FDA based the EUA based on the randomized, double-blind, placebo-controlled evaluation of protease inhibition of COVID-19 in the High-Risk Patients Trial (EPIC-HR), which looked at nirmatrelvir treatment in non-hospitalized, high-risk, asymptomatic COVID-19 patients. 19.

In a recent study published in search field* Preprint server, researchers evaluated the effectiveness of nirmatrelvir in preventing COVID-19-related death and hospitalization in high-risk patients.

about studying

This study used data from computerized medical records for the Comprehensive Health Services (CHS), a large healthcare institution 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 the drug was given to CHS patients. Patients diagnosed with COVID-19 by February 24, 2022 were eligible to participate in the study.

the findings

A total of 109,213 individuals fulfilled the study inclusion criteria. The average age of the study participants was 60, with 39% of the participants. Obesity, diabetes and smoking were the most common co-morbidities. 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 nirimatilvir. Participants 65 years of age or older who had recently been diagnosed with cancer had significantly higher uptake. Participants who did not have COVID-19 immunization and members of the Arab minority group significantly underestimated intake.

The author presented results for the age groups over 65 and under 65 separately because testing for the interaction of nimatelvir with other variables showed significant differences according to age group.

Hospital admissions associated with COVID-19 occurred in 343 out of 1,435 treated patients and 334 out of 64,959 untreated patients out of 66,394 patients aged 40–64 years. COVID-19-related hospitalizations occurred in 776 out of 42,819 patients age 65 and older, 14 of 2,504 treated patients, and 762 out of 40,315 untreated patients. Low levels of immunity to COVID-19 and previous hospitalizations were features most associated with a higher rate of COVID-19-related hospitalizations in both age groups. In the 40-64 age group, immunosuppression was strongly associated with hospitalization.

Hospital admissions associated with COVID-19 were reported in 182 of 20,531 patients with no prior immunity and 161 of 45,863 patients with prior immunity in patients aged 40 to 64 years. 39,513 patients with pre-existing immunity were among the participants aged 65 and over.


During the Omicron variant mutation, the drug nirmatrelvir was associated with a significant decrease in COVID-19 hospital admissions and death rates in people aged 65 and older. Although this was an observational study, the results and the apparent potential for severe COVID-19 prevention could help decision makers allocate a limited supply of those for whom nirmatrelvir has been shown to be successful.

*Important note

Research Square publishes primary scientific reports that have not been peer-reviewed, and therefore should not be considered conclusive or guide clinical practice/health-related behaviour, or treated as established information.

2022-06-02 13:13:00

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