Patients who received nirmatrelvir plus ritonavir (Paxlovid) had lower risk of both hospitalization within 14 days and death within 28 days compared with patients who did not receive the treatment.
The use of nirmatrelvir plus ritonavir further (Paxlovid) reduces the already low risk of hospitalization among older vaccinated patients who contract COVID-19, found researchers of a new study published in Annals of Internal Medicine.
The observational retrospective study adds insight into the use of nirmatrelvir plus ritonavir among patients who are vaccinated against COVID-19. Although recommended for patients regardless of vaccination status when it received emergency use authorization at the end of 2021, the treatment was only studied in unvaccinated patients in the Evaluation of Protease Inhibition for COVID-19 in High-Risk Patients (EPIC-HR) trial.
“Emerging data involving the initial Omicron variants show a potential benefit of nirmatrelvir plus ritonavir regardless of vaccination status, but only a small proportion of the eligible patient populations in these studies were treated,” explained the researchers. “A better understanding of the clinical effectiveness of nirmatrelvir plus ritonavir is needed to inform individual and public health decisions, particularly among vaccinated persons infected by Omicron strains.”
The researchers analyzed outcomes from among more than 44,000 patients aged 50 or older with COVID-19 who were not hospitalized, 28.1% of which received nirmatrelvir plus ritonavir.
Patients who received nirmatrelvir plus ritonavir had lower risk of both hospitalization within 14 days (adjusted risk ratio [aRR], 0.60; 95% CI, 0.44-0.81) and death within 28 days (aRR, 0.29; 95% CI, 0.12-0.71) compared with patients who did not receive the treatment. Hospitalization or death occurred in 0.55% (n = 69) of patients who received nirmatrelvir plus ritonavir compared with 0.97% (n = 310) of patients who did not receive the treatment.
“This study confirms the effectiveness of nirmatrelvir plus ritonavir in preventing hospitalization and death among vaccinated and unvaccinated persons aged 50 years or older with COVID-19,” reflected the researchers. “Although these data suggest its clinical impact may be reduced in the context of high levels of prior immunity and consequent lower risk, the estimated 40% reduction in hospitalization and 71% reduction in death could have large population benefits if nirmatrelvir plus ritonavir is used widely.”
Patients who received the combination treatment were more likely to be older, have higher comorbidity scores, be fully vaccinated, and have a recent receipt of a vaccine dose. Reductions in hospitalizations and death seen with nirmatrelvir plus ritonavir were consistent among subgroups, including age groups, comorbidity scores, and body mass index.
Notably, the treatment combination yielded increased protection in patients not fully vaccinated and in patients who received their latest dose more than 20 weeks prior. There was an 81% risk reduction in a subgroup of incompletely vaccinated patients. The researchers noted that the large risk reduction seen among unvaccinated patients was similar to the findings from the EPIC-HR trial.
Dryden-Peterson S, Kim A, Kim A, et al. Nirmatrelvir plus ritonavir for early COVID-19 in a large U.S. health system. Ann Intern Med. Published online December 13, 2022. doi:10.7326/M22-2141