Pasadena, CA—COVID-19 patients who received Paxlovid on the day of their positive test reduced their risk of hospitalization or death from the infection 90%, according to a new Kaiser Permanente study. Effectiveness was somewhat lower with delays, the study noted.

In an article published in Lancet Infectious Disease, researchers confirmed the benefit of Paxlovid (nirmatrelvir-ritonavir) as an early-stage treatment to prevent hospitalization for people with mild-to-moderate COVID-19, regardless of prior immunity or age.

“Among Kaiser Permanente members in Southern California who tested positive for coronavirus infection, receiving Paxlovid within 5 days of the start of COVID-19 symptoms was associated with substantial reductions in the risk of hospital admission or death,” explained senior author Sara Tartof, PhD, an epidemiologist with the Kaiser Permanente Southern California Department of Research & Evaluation. “These findings are even more notable because in this population with high levels of vaccination, we still see additional benefits of this treatment.”

Background information in the articles pointed out that, in the United States, oral nirmatrelvir-ritonavir is authorized for use by patients aged 12 years or older with mild-to-moderate SARS-CoV-2 infection who are at risk for progression to severe COVID-19, including hospitalization. The Kaiser Permanente authors advised, however, that effectiveness under current real-world prescribing practices in outpatient settings was not known.

To remedy that, the researchers conducted matched observational cohort study of nonhospitalized cases with SARS-CoV-2 infection; they compared outcomes among patients who received or did not receive nirmatrelvir-ritonavir within the Kaiser Permanente Southern California healthcare system.

For the study, cases were matched on:

• Testing date
• Age
• Sex
• Clinical status (including care received, presence or absence of acute COVID-19 symptoms at testing, and time from symptom onset to testing)
• History of vaccination
• Charlson comorbidity index
• Prior-year healthcare utilization
• BMI.

In addition to the primary analysis focusing on hospital admission or death within 30 days after a positive test, the secondary analyses evaluated effectiveness against ICU admission, mechanical ventilation, or death within 60 days after a positive test.

The participants included in the analysis were 7,274 nirmatrelvir-ritonavir recipients and 126,152 nonrecipients with positive results from SARS-CoV-2 tests undertaken in outpatient settings between April 8, 2022, and October 7, 2022. The majority (85.6% and 6.3%) had received 2+ and 3+ COVID-19 vaccine doses, respectively. Most (83.6%) of the patients were symptomatic at the point of testing, with 75.2% of treatment recipients and 67.1% of nonrecipients testing within 0 to 5 days after symptom onset.

The results indicated that effectiveness in preventing hospital admission or death within 30 days after a positive test was 79.6% for cases dispensed nirmatrelvir-ritonavir within 0 to 5 days after symptom onset. More specifically:

• Within the subgroup of patients who were dispensed Paxlovid on the day of their positive COVID-19 test, effectiveness was 90%.
• Effectiveness dropped to 44% for patients who received Paxlovid 6 or more days after symptom onset or for cases not experiencing acute clinical symptoms.
• Overall, for patients who received Paxlovid at any time within their clinical course, effectiveness was 54%.

As for the secondary outcome, effectiveness in preventing ICU admission, mechanical ventilation, or death within 60 days after a positive COVID-19 test was 89% for patients who were dispensed Paxlovid 0 to 5 days after symptom onset and 84% for people who received Paxlovid treatment at any time.

“In a setting with high levels of COVID-19 vaccine and booster uptake, receipt of nirmatrelvir-ritonavir 0-5 days after symptom onset was associated with substantial reductions in risk of hospital admission or death within 30 days after a positive outpatient SARS-CoV-2 test,” the authors concluded.

The content contained in this article is for informational purposes only. The content is not intended to be a substitute for professional advice. Reliance on any information provided in this article is solely at your own risk.

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