News - 10 November 2021

Paxlovid: Pfizer drug has 89% efficacy against Covid-19

Preliminary results from an experimental study of Pfizer’s new drug for Covid-19 are very promising, with an 89% efficacy rate in reducing the risk of hospitalisation and death. This follows a product from Merck that will reduce risk among patients predisposed to a severe form of Covid-19.


During ongoing clinical trials of Paxlovid, the drug has been shown to reduce the risk of hospitalisation or death in adults at risk of severe Covid-19 by almost 90%. These positive test results prompted Pfizer to stop the experimental studies ahead of schedule and begin efforts to register the drug under a special procedure. The results of the trials are to be submitted to the US Food and Drug Administration, which will decide whether the formulation will be eligible for the accelerated drug approval programme.

Paxlovid clinical trials

The clinical trials were conducted on a group of more than 1,200 patients who had at least one factor that increased the risk of severe Covid-19. These factors included obesity and advanced age. The trials aimed to examine patients who had mild to moderate Covid-19 infection for their risk of hospitalisation and death.


Study participants were divided into several groups that received the drug or placebo within three or more days of the onset of symptoms of Covid-19 infection. Among patients taking Paxlovid within three days of the onset of symptoms, only 0.8 per cent were hospitalised. Furthermore, none of these participants died within 28 days of administration. In contrast, in the group that received a placebo, 7% of patients were hospitalised and seven of them died. Similar results were observed in the groups of people who received the drug a few days later after the onset of symptoms. Approximately 1% of those who took Paxlovid was admitted to hospitals, and 6.7% of those in the placebo group were admitted to hospitals. Deaths occurred only in the placebo group, and 10 people died as a result of the infection.

Antiviral drugs

It is important to remember that the effectiveness of antiviral drugs depends on the timing of their administration. The patient must receive the drugs as soon as possible so that the infection cannot develop. Paxlovid is a drug from the group of protease inhibitors and works by blocking the enzyme that allows the virus to multiply. The drug, developed by Pfizer, has to be administered twice a day, and patients have to take three tablets of the product at a time.


Another antiviral drug is Molnupiravir from Merck. The product is a ribonucleoside analogue that builds into the genetic material of the virus and prevents it from further replication. The task of this drug is therefore to introduce errors into the genetic code of the virus. The drug was approved in the UK last week, and research by a form of Merck shows that it reduces the risk of hospitalisation or death for adults at risk of severe Covid-19 by 50%.

Efficacy and availability of the Paxlovid drug

As Annaliesa Anderson, representing Pfizer, explained to Reuters, the high efficacy of the drug, given even five days after the onset of the disease, can dramatically reduce the number of hospitalisations. Implementing the treatment at an early stage of the disease will allow faster treatment, which in turn will be associated with benefits from a public health point of view. As Pfizer CEO Albert Bourla adds, based on the data collected, the new drug will alleviate Covid-19 infections and could prevent 9 out of 10 hospitalisations.


For now, the company is not giving details of side effects but admits that they occurred in 20% of subjects, both in the group taking the drug and in the group receiving a placebo.


Pfizer wants to produce 180,000 packs of the drug by the end of the year. Plans for 2022 call for the production of no less than 50 million packs. However, the company says that production objectives may be updated soon.


Currently, the company will test the effect of the drug on patients without a predisposition to a severe form of infection and will also consider whether it is worth using the drug as a preventive measure in people who have been in contact with the virus. Additionally, experts explain that vaccination is still the best way to protect against Covid-19 because it significantly nullifies the possibility of severe Covid-19 infection and thus eliminates the need for subsequent treatment.

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Agnieszka Skonieczna

Market Analysis Director