Nirmatrelvir-Ritonavir Reduces COVID-19 Admissions in Partially-Vaccinated Patients

Results of a study published in Clinical Infectious Diseases show that treatment with nirmatrelvir-ritonavir is associated with reduced risk for COVID-19-related hospitalization among partially-vaccinated high-risk outpatients.

Researchers conducted a retrospective cohort study in Canada between March and October of 2022 to assess whether nirmatrelvir-ritonavir reduces the risk for COVID-19-related hospitalization among high-risk patients. Eligible patients were those who received 1 prescription for nirmatrelvir-ritonavir from community pharmacies. Patients who received treatment were compared against infected individuals who did not receive treatment (controls) via 1:1 nearest neighbor propensity score matching. Poisson regression was used to determine the relative risk (RR) for COVID-19-related hospitalization within 30 days of the index date.

After propensity score matching, the treatment and control groups each consisted of 8402 patients. Among all patients, 57% were aged 60 years and older, 58% were women, 56% were partially vaccinated, and 51% had at least 5 comorbidities.

The researchers found that nirmatrelvir-ritonavir treatment significantly reduced the risk for COVID-19-related hospitalization by 69% (RR, 0.31; 95% CI, 0.28-0.36; P <.001), irrespective of vaccination status.

Further analysis showed that the association between nirmatrelvir-ritonavir and reduced risk for COVID-19-related hospitalization was more significant among patients who were partially vaccinated (RR, 0.04; 95% CI, 0.03-0.06; P <.001). However, receipt of nirmatrelvir-ritonavir had no significant effect on hospitalization risk among patients who were fully vaccinated (RR, 0.93; 95% CI, 0.78-1.09; P =.321).

Similar results were indicated in multivariable analyses.  

Among fully-vaccinated patients who were severely immunocompromised, treatment with nirmatrelvir-ritonavir reduced hospitalization risk by 34% (RR, 0.66; 95% CI, 0.50-0.89; P =.005), irrespective of the time since receipt of the last vaccine dose.

In high-risk patients aged 70 years and older, treatment with nirmatrelvir-ritonavir reduced hospitalization risk by 25% (RR, 0.75; 95% CI, 0.63-0.88; P <.001). Of note, the reduction in hospitalization risk for patients in this group was more significant among those whose received their last vaccine dose more than 6 months prior (RR, 0.50; 95% CI, 0.34-0.74; P <.001).

Study limitations include a potential lack of generalizability to other settings due to the criteria for access to nirmatrelvir-ritonavir treatment. Other limitations include a lack of data on sociodemographic characteristics, COVID-19 severity, and the severity of comorbidities.

According to the researchers, “Nirmatrelvir/ritonavir [is] one of the preferred treatment options for infected outpatients at high risk for severe COVID-19, especially since several alternative options are not able to neutralize certain variants of SARS-CoV-2.”

Disclosures: Multiple authors declared affiliations with pharmaceutical, biotech, and/or device companies. Please see the original reference for a full list of disclosures.

This article originally appeared on Infectious Disease Advisor