This year, another COVID-19 summer surge is noted in the US. In most of the patients, an antiviral drug called Paxloid has been prescribed, the generic name of which is nirmatrelvir-ritonavir.
Nirmatrelvir-ritonavir is currently the only approved oral therapy for COVID-19 and is indicated for the treatment of mild to moderate SARS-CoV-2 infection in adults and pediatric patients ≥12 years of age and weighing ≥40 kg with high risk of progression to severe disease. These include persons aged 50 years or older, especially those aged ≥65 years, but also younger people with any of a long list of comorbidities that predispose to severe COVID-19.
The clinical trials that led to the FDA authorizing emergency use of nirmatrelvir-ritonavir in December 2021 and approving it in May this year were conducted with unvaccinated people who were infected with the now long-gone SARS-CoV-2 Delta variant. This has raised questions over its effectiveness for people who have been vaccinated or who have been infected with sub variants of Delta’s successor Omicron that have been circulating for almost three years.
But recent observational studies suggest nirmatrelvir-ritonavir still protects people at high risk against hospitalization and death from COVID-19. As the number of people with post-acute sequelae of SARS-CoV-2 infection, or long COVID, grows, scientists have been investigating whether nirmatrelvir-ritonavir might be useful in protecting against or treating the condition.
Does It Still Prevent Severe COVID-19?
Scientists from Pfizer, which markets nirmatrelvir-ritonavir, and coauthors recently published a systematic literature review examining that question. They searched for real-world studies reported from December 2021 through March 2023 and identified 18 that met their final selection criteria.
The evidence showed that nirmatrelvir-ritonavir was effective irrespective of age category, underlying high-risk conditions, and vaccination status. Treatment with nirmatrelvir-ritonavir also strongly reduced postinfection risk for all-cause and COVID-19–related mortality both within the first 30 days and in the long run. The greatest associated reduction in postinfection risk was seen for treatment initiated within 5 days of symptom onset, as recommended on the label.
“We remain very confident in Paxlovid’s clinical effectiveness at preventing severe outcomes, including hospitalization and death, from COVID-19 in the patients at high risk of severe disease,” said Kit Longley, a Pfizer spokesperson, in an early August email.
Yet another study published recently came to a somewhat different conclusion.
Indeed, evidence suggested that nirmatrelvir-ritonavir had small but significant efficacy in reducing hospitalization due to COVID-19 and all-cause mortality among individuals with laboratory-confirmed mild to moderate infections, though the evidence is weak, and more studies are needed, concluded the authors.
Reference:
Rubin R. The latest research about Paxlovid: Effectiveness, access, and possible long COVID benefits. JAMA [Internet]. 2024 [cited 2024 Sep 10]; Available from: https://jamanetwork.com/journals/jama/fullarticle/2823578
