COVID-19 Pharmaceuticals

The Implications of Pfizer’s New Antiviral COVID-19 Pill, Paxlovid

Donna Mahboubi—McMaster Health Sciences 2026

Chances are you’ve heard mentions of a COVID-19 pill, but you may be wondering, “What actually is it?” There are many emerging treatments for COVID-19 meant for people who are already infected with the virus, including treatments taken orally. These treatments differ from vaccinations because they actively treat the virus whereas vaccines are used as a preventative measure to avoid getting infected in the first place. Similarly to the COVID-19 vaccines, however, Pfizer is one of the first to hop onto the COVID-19 pill train, having created the first FDA-approved oral treatment for COVID-19, Paxlovid (1).

What exactly is Paxlovid?

Paxlovid is the combination of two nirmatrelvir pills and one ritonavir pill, all taken twice a day over the span of five days (2). Nirmatrelvir, a drug created by Pfizer, is the drug in Paxlovid that contains Paxlovid’s antiviral properties, limiting the replication of the virus (2). Ritonavir, an existing drug typically used in the treatment of HIV/AIDS among other things, allows nirmatrelvir to remain in the body at higher concentrations for longer periods of time; it does this by being a CYP, cytochrome P450, inhibitor (3). CYPs are enzymes that are involved in the termination of many drugs, including nirmatrelvir, so inhibiting them enhances and prolongs the antiviral properties of nirmatrelvir. It is recommended that Paxlovid is taken within five days of symptom onset (1).



Nirmatrelvir and ritonavir clearly work together to create a powerhouse of a COVID-19 treatment that demonstrates immense benefits. A nearly five-month-long clinical trial conducted by Pfizer, which concluded in December 2021, showed an 89% decrease in severe illness and death when the drug was taken within three days of symptom onset as compared to a placebo (4). This trial, called EPIC-HR was done on adults who present a high risk of COVID-19 progressing to a severe illness. In the same trial, 0.7% of patients who received Paxlovid were hospitalized as opposed to 6.5% who received the placebo being hospitalized or dying (4). In a second trial, EPIC-SR, done on adults at a more standard risk, hospitalization was reduced by 70% as compared to the placebo (4).

However, Paxlovid is not perfect. It’s not recommended for certain populations such as those with severe kidney or liver impairments (1). A lack of research also makes it difficult to prescribe to certain populations such as people under 40 kilograms, pregnant or lactating people, and those on drugs that could have potentially dangerous interactions with Paxlovid (5).

Implications and the Future

Paxlovid has not only paved the way for other COVID-19 antiviral pills, but also for other forms of COVID-19 treatments. These include antiviral-type treatments, such as the oral treatments Paxlovid and Molnupiravir, and the intravenous treatment Remdesivir (6). Monoclonal antibodies are another form of COVID-19 treatment that improve the immune system’s response to the virus as opposed to targeting the actual virus itself. Bebtelovimab is a monoclonal antibody that combats COVID-19 through intravenous injection (6). Paxlovid is just the beginning, and the creation of new COVID-19 treatments can improve the accessibility of a treatment for those who can not take Paxlovid for a multitude of reasons or in situations where Paxlovid is not available.


The accessibility of Paxlovid has actually been a large issue. This is in part due to the lack of transparency that producers of Paxlovid have demonstrated, particularly in the realm of costs and remaining supply. The lack of transparency has led to challenges in lower-income countries receiving the treatments, resulting in the WHO declaring its concerns regarding Paxlovid accessibility (5). The COVID-19 pandemic has already led to great global divides, and Paxlovid’s limited accessibility gives it the potential to further increase disparities within global health.

Although the future of COVID-19 treatments and the potentially negative implications of Paxlovid are greatly unknown, its introduction into the world of healthcare is quite beneficial and exciting. Paxlovid has opened up a new realm of research within the topic of COVID-19 and has provided an amazing opportunity for collaboration to lead to many incredible discoveries!


  1. Louisiana Department of Health. FDA authorizes first antiviral pills for COVID-19 [Internet]. [cited 2022 Nov 28]. Available from:
  1. Yeboah N, Nijjar H, Piper D. How does Pfizer’s COVID-19 pill work, and who will get it? | CBC News [Internet]. CBC. 2022 [cited 2022 Nov 28]. Available from:
  1. NIH. Paxlovid Drug-Drug Interactions | COVID-19 Treatment Guidelines [Internet]. [cited 2022 Nov 28]. Available from:–paxlovid-/paxlovid-drug-drug-interactions/
  1. Pfizer. 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 [Internet]. [cited 2022 Nov 28]. Available from:
  1. Jerving S. WHO recommends Pfizer’s COVID-19 pill, but poor nations may lack access [Internet]. Devex. 2022 [cited 2022 Nov 28]. Available from:
  1. CDC. COVID-19 and Your Health [Internet]. Centers for Disease Control and Prevention. 2020 [cited 2022 Nov 28]. Available from:
  1. CBC News. How do I get the COVID-19 medication Paxlovid? | CBC News [Internet]. CBC. 2022 [cited 2023 Jan 11]. Available from:
  1. CDC. COVID-19 and Your Health [Internet]. Centers for Disease Control and Prevention. 2020 [cited 2023 Jan 11]. Available from:

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