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0 0.5 1 1.5 2+ Hospitalization 51% Improvement Relative Risk Paxlovid for COVID-19  Shah et al.  EARLY TREATMENT Is early treatment with paxlovid beneficial for COVID-19? Retrospective 699,848 patients in the USA Lower hospitalization with paxlovid (p<0.000001) Confounding by health-seeking and additional untracked treatments and measures may substantially overestimate efficacy Shah et al., American J. Transplantation, Jan 2023 Favors paxlovid Favors control

Paxlovid associated with decreased hospitalization rate among adults with COVID-19 — United States, April–September 2022

Shah et al., American Journal of Transplantation, doi:10.1016/j.ajt.2022.12.004
Jan 2023  
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Retrospective 699,848 outpatients with COVID-19 showing lower hospitalization with paxlovid.
Confounding by treatment propensity. This study analyzes a population where only a fraction of eligible patients received the treatment. Patients receiving treatment may be more likely to follow other recommendations, more likely to receive additional care, and more likely to use additional treatments that are not tracked in the data (e.g., nasal/oral hygiene, (B), vitamin D (C), etc.) — either because the physician recommending paxlovid also recommended them, or because the patient seeking out paxlovid is more likely to be familiar with the efficacy of additional treatments and more likely to take the time to use them. Malden et al. confirm significant bias in the use of paxlovid, showing that treated patients are more likely to be from affluent neighborhoods, be more health-conscious, and have better access to care. Therefore, these kind of studies may overestimate the efficacy of treatments.
Confounding by contraindication. Hoertel et al. find that over 50% of patients that died had a contraindication for the use of Paxlovid Hoertel. Retrospective studies that do not exclude contraindicated patients may significantly overestimate efficacy.
Black box warning. The FDA notes that "severe, life-threatening, and/or fatal adverse reactions due to drug interactions have been reported in patients treated with paxlovid" FDA.
This study is excluded in the after exclusion results of meta analysis: only a fraction of eligible patients received treatment and these patients may be more likely to follow other recommendations, receive additional care, and more more likely to use additional untracked treatments such as vitamin D and nasal/oral hygiene.
risk of hospitalization, 51.0% lower, HR 0.49, p < 0.001, adjusted per study, multivariable, Cox proportional hazards, RR approximated with OR.
Effect extraction follows pre-specified rules prioritizing more serious outcomes. Submit updates
Shah et al., 31 Jan 2023, retrospective, USA, peer-reviewed, 11 authors. Contact:
This PaperPaxlovidAll
Report from the CDC: MMWR Paxlovid associated with decreased hospitalization rate among adults with COVID-19 -United States, April-September 2022
MD Melisa M Shah, Brendan Joyce, MBBS Ian D Plumb, MS Sam Sahakian, PhD Leora R Feldstein, Eric Barkley, MSP Mason Paccione, PhD Joseph Deckert, MPH Danessa Sandmann, MD Jacqueline L Gerhart, MD Melissa Briggs Hagen
What is already known about this topic? Nirmatrelvir-ritonavir (Paxlovid) is an outpatient antiviral medication recommended for adults with mild-to-moderate COVID-19 who have elevated risk of severe illness. What is added by this report? Among U.S. adults diagnosed with COVID-19, including those with previous infection or vaccination, persons who were prescribed Paxlovid within 5 days of diagnosis had a 51% lower hospitalization rate within 30 days after diagnosis than those who were not prescribed Paxlovid. What are the implications for public health practice? Paxlovid should be offered to eligible adults irrespective of vaccination status, especially in groups with the highest risk for severe COVID-19 outcomes, such as older adults and those with multiple underlying health conditions. Nirmatrelvir-ritonavir (Paxlovid), an oral antiviral treatment, is authorized for adults with mild-to-moderate COVID-19 who are at increased risk for progression to severe illness. However, real-world evidence on the benefit of Paxlovid, according to vaccination status, age group, and underlying health conditions, is limited. To examine the benefit of Paxlovid in adults aged !18 years in the United States, a large electronic health record (EHR) data set (Cosmos y ) was analyzed to assess the association between receiving a prescription for Paxlovid and hospitalization with a COVID-19 diagnosis in the ensuing 30 days. A Cox proportional hazards model was used to estimate this association, adjusted for demographic characteristics, geographic location, vaccination, previous infection, and number of underlying health conditions. Among 699,848 adults aged !18 years eligible for Paxlovid during April-August 2022, 28.4% received a Paxlovid prescription within 5 days of COVID-19 diagnosis. Being prescribed Paxlovid was associated with a lower hospitalization rate among the overall study population (adjusted hazard ratio [aHR] ¼ 0.49), among those who had received !3 mRNA COVID-19 vaccines (aHR ¼ 0.50), and across age groups (18-49 years: aHR ¼ 0.59; 50-64 years: aHR ¼ 0.40; and !65 years: aHR ¼ 0.53). Paxlovid should be prescribed to eligible adults to reduce the risk of COVID-19-associated hospitalization. Paxlovid is an oral antiviral medication that received Emergency Use Authorization by the Food and Drug Administration on December 22, 2021 (1), for use in patients with mild-to-moderate COVID-19 at high risk for progression to severe illness. Eligibility for Paxlovid includes 1) receipt of a positive SARS-CoV-2 test result (including home antigen test), 2) symptoms consistent with mild-to-moderate COVID-19, 3) symptom onset within the past 5 days, 4) age !18 years (or age !12 years and weight !40 kg), 5) one or more risk factors for progression to severe COVID-19, 6) no known or suspected severe renal or hepatic impairment, 7) no history of clinically significant reactions (e.g., toxic epidermal necrolysis or Stevens-Johnson syndrome) to the active ingredients..
Arbel, Sagy, Hoshen, Nirmatrelvir use and severe Covid-19 outcomes during the Omicron surge, N Engl J Med, doi:10.1056/NEJMoa2204919
Dryden-Peterson, Kim, Kim, Nirmatrelvir plus ritonavir for early COVID-19 and hospitalization in a large US health system, doi:10.1101/2022.06.14.22276393
Ganatra, Dani, Ahmad, Oral nirmatrelvir and ritonavir in nonhospitalized vaccinated patients with coronavirus disease 2019 (COVID-19), Clin Infect Dis, doi:10.1093/cid/ciac673
Hammond, Leister-Tebbe, Gardner, Oral nirmatrelvir for high-risk, nonhospitalized adults with Covid-19, N Engl J Med, doi:10.1056/NEJMoa2118542
Lewnard, Malden, Hong, Effectiveness of nirmatrelvir-ritonavir against hospital admission: a matched cohort study in a large US healthcare system, doi:10.1101/2022.10.02.22280623
Najjar-Debbiny, Gronich, Weber, Effectiveness of Paxlovid in reducing severe coronavirus disease 2019 and mortality in high-risk patients, Clin Infect Dis, doi:10.1093/cid/ciac443
Vangeel, Chiu, Jonghe, Remdesivir, molnupiravir and nirmatrelvir remain active against SARS-CoV-2 Omicron and other variants of concern, Antiviral Res, doi:10.1016/j.antiviral.2022.105252
Wong, Au, Lau, Lau, Cowling et al., Real-world effectiveness of molnupiravir and nirmatrelvir/ritonavir among COVID-19 inpatients during Hong Kong's Omicron BA.2 wave: an observational study, Lancet Infect Dis, doi:10.1016/S1473-3099(22)00507-2
Yek, Warner, Wiltz, Risk factors for severe COVID-19 outcomes among persons aged !18 years who completed a primary COVID-19 vaccination series-465 health care facilities, United States, December 2020-October 2021, MMWR Morb Mortal Wkly Rep, doi:10.15585/mmwr.mm7101a4
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