How effective is Paxlovid for COVID-19?
How effective is Pfizer's COVID-19 pill?
- Final data of a study (ERIC-HR Phase 2/3 ) shows when Paxlovid is taken within 3 days of COVID-19 symptom onset, it successfully decreases the risk of being hospitalized by 89% for patients that are at high risk of COVID-19 progressing to severe illness. When taken within 5 days of symptom onset, Paxlovid reduces the risk of being hospitalized by 88%.
- Paxlovid contains two co-packaged medicines nirmatrelvir (previously known as PF-07321332) and ritonavir.
- Paxlovid contains oral tablets that are best taken at the first sign of symptoms, after a positive Sars-CoV-2 test. It is taken to help decrease the number and severity of symptoms or avoid severe illness which may lead to hospitalization or death.
- On December 22, 2021 the FDA issued an Emergency Use Authorization (EUA) for Paxlovid to be used for treatment of mild-to-moderate COVID-19, in patients who have increased risk of hospitalization or death. Patients must be 12 years or older and weigh at least 40kg (88lb), and have a positive Sars-CoV-2 viral test (the virus that causes COVID-19).
How does Paxlovid work?
- Paxlovid contains co-packaged nirmatrelvir tablets and ritonavir tablets that are taken orally at the first sign of COVID-19 illness, after a positive Sars-CoV-2 viral test.
- Nirmatrelvir works by blocking an enzyme (called SARS-CoV-2-3CL protease) that the coronavirus needs to replicate.
- As the virus can not reproduce itself this reduces the severity of symptoms and so decreases the number of hospitalizations and deaths in high risk patients.
- Ritonavir is an HIV medication that slows the metabolism of nirmatrelvir which helps nirmatrelvir stay in the body longer and a higher concentration, making it more effective.
How do you take Paxlovid?
Paxlovid is prescribed as medicine to be taken at home, for high-risk patients to avoid severe COVID-19 illness, including hospitalization and death. Paxlovid will be one box containing a full five day treatment course with oral nirmatrelvir tablets and ritonavir tablets.
- Paxlovid should be started as soon as possible after a positive Sars-CoV-2 viral test and within 5 days of the first symptoms.
- Nirmatrelvir 300mg (two 150mg tablets) taken twice daily for five days.
- Ritonavir 100mg taken twice daily for five days.
When will it be available?
Paxlovid was issued an Emergency Use Authorization by the FDA on December 22, 2021. Pfizer is expected to start delivery immediately, as it has a supply agreement with the U.S. government that was announced in November 2021.
Does Paxlovid treat Omicron?
- The Omicron variant of COVID-19 was first detected in mid November 2021.
- Recent information from Pfizer indicated that Paxlovid will retain robust antiviral activity against the Omicron variant, as in vitro data confirmed that Paxlovid is a potent inhibitor of the Omicron 3CL protease
- Additional studies the Omicron variant are also underway.
Clinical Trials for Paxlovid.
Patients at HIGH RISK of hospitalization with COVID-19
Paxlovid has an EUA for treating mild to moderate COVID-19, in patients at high risk of severe COVID-19.
Final results from Phase 2/3 ERIC-HR study of the antiviral pill Paxlovid shows it successfully decreases the risk of being hospitalized by 89% for patients that are at high risk of COVID-19 progressing to severe illness. Paxlovid or placebo was taken within 3 days of first COVID-19 symptoms and the results were:
- 0.7% (5 out of 697) of the Paxlovid patients were hospitalized with no deaths.
- 6.5% (44 out of 682) of the placebo patients were hospitalized with 9 deaths.
- Paxlovid patients also had a 10-fold decrease in viral load compared to the placebo group.
Patients at STANDARD RISK of hospitalization with COVID-19
Paxlovid is NOT authorised for COVID-19 patients who have standard risk of hospitalization with COVID-19
Early results from a trial (Phase 2/3 EPIC-SR) looking at Paxlovid use in Covid-19 patients at standard risk of hospitalization, showed a 70% reduction in hospitalization in the Paxlovid patients compared to placebo.
- 0.7% (3 out of 428) of the Paxlovid patients were hospitalized with no deaths.
- 2.4% (10 out of 426) of the placebo patients were hospitalized with no deaths.
- Paxlovid patients also had a 10-fold decrease in viral load compared to the placebo group, which was the same as Phase 2/3 ERIC-HR study.
Can Paxlovid prevent COVID-19?
Post-Exposure Prophylaxis of COVID-19 using Paxlovid
Paxlovid is NOT authorized to be used to prevent COVID-19.
There is an ongoing study (Phase 2/3 EPIC-PEP) looking at how well Paxlovid works at preventing COVID-19 in patients who have been exposed to COVID-19 by a household member. This is an on-going study on COVID-19 post-exposure prophylaxis and results are not yet available.
Click here for more information on: Paxlovid: Uses, Doses, Side Effects and Interactions.
- Paxlovid (nirmatrelvir and ritonavir tablets) has been issued an Emergency Use Authorization for treatment of mild-to-moderate COVID-19 in patients who are at high risk for progression to severe COVID-19, to help reduce the severity of COVID-19 symptoms and also decrease the number of hospitalizations and deaths.
- Pfizer’s Novel COVID-19 Antiviral Treatment Candidate Reduced Risk of Hospitalization or Death by 89% in Interim Analysis of Phase ⅔ EPIC-HR Study [Accessed December 14, 2021] https://www.pfizer.com/news/press-release/press-release-detail/pfizers-novel-covid-19-oral-antiviral-treatment-candidate
- PF-07321332 Early Data suggest Pfizer Pill May Prevent Severe COVID-19 [Accessed December 14, 2021] https://directorsblog.nih.gov/tag/pf-07321332/
- Pfizer Announces Additional Phase 2/3 Study Results Confirming Robust Efficacy of Novel COVID-19 Oral Antiviral Treatment Candidate in Reducing Risk of Hospitalization or Death. [Accessed December 15, 2021] https://www.pfizer.com/news/press-release/press-release-detail/pfizer-announces-additional-phase-23-study-results
- FDA Grants Emergency Use Authorization for Pfizer's Paxlovid Pill as First At-Home COVID-19 Treatment. [Accessed December 23, 2021] https://www.drugs.com/news/fda-oks-pfizer-pill-first-home-covid-102454.html
- Coronavirus (COVID-19) Update: FDA Authorizes First Oral Antiviral for Treatment of COVID-19 [Accessed December 23, 2021] https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-first-oral-antiviral-treatment-covid-19?utm_medium=email&utm_source=govdelivery
- FACT SHEET FOR HEALTHCARE PROVIDERS: EMERGENCY USE AUTHORIZATION FOR PAXLOVID. [Accessed December 23, 2021] https://www.fda.gov/media/155050/download?utm_medium=email&utm_source=govdelivery
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