Salut, Covid-19, Vacunes

Pfizer did not adulterate vaccine clinical trial evidence to gain FDA approval

An article is circulating on several Telegram groups claiming that NPR, public radio in the United States, has reported that Pfizer "violated the scientific intent" of the covid-19 vaccine clinical trials by allegedly giving the Pfizer injection to the control group, and therefore "any real benefit or safety issues cannot be substantiated". This is FALSE. Neither has the public radio said any such thing, nor is there any indication that Pfizer vaccinated the control group during the clinical trials of its vaccine. 

"As reported by NPR [...] the intentional dilution of the placebo group violates the scientific purpose of testing whether the vaccine has any efficacy; any real benefit and/or safety issues cannot be evidenced, since without a control group, there is nothing to compare the vaccinated group to."

This assertion is taken from the article, which is supposedly based on an NPR article. But that is not what the American radio station said. As they state on their website, what happened is that some of those participants who were in the placebo group (i.e. the solution they were given was not the vaccine in order to compare the results in the clinical trials) voluntarily decided to receive the vaccine, but this was after the results of the phase III clinical trial were published and the vaccine was approved by the FDA

That is, once the efficacy of the Pfizer injection was confirmed, some of the people who had not yet been vaccinated (they did not know whether they had been vaccinated or not) and had received a placebo decided freely to do so. Others, on the other hand, continued to take part in the study, which was no longer focused on measuring the efficacy of the vaccine, but on other aspects such as long-term side effects.

This type of move is a common occurrence in the research world. In fact, the studies concerning the Pfizer and Moderna vaccines are expected to last until October 2023 and 2022, respectively. The aim is to constantly monitor the safety of the vaccine, in case of any unforeseen events, and some of those in the control group will remain unvaccinated. 

More than documented clinical trials

In another part of the article you have sent us, it is stated that "there is no way to measure the efficacy, effectiveness or safety of the vaccine itself", since without a control group, it is supposedly impossible to compare them with those who have received the dose. 

However, there are studies published in peer-reviewed scientific journals that indicate not only how many people participated in the study (43.448 for Pfizer, 30.420 for Moderna), but also how many of them received the vaccine and how many received the placebo. By the time the data from the phase III study were analysed and published, placebo participants who wanted to had purchased the injection. 

That, according to an opinion article authored by a group of experts from the World Health Organisation in the New England Journal of Medicine, is up to each participant to decide, but in their view "would miss the opportunity to obtain reliable evidence on longer-term effects". 

The address of the page on which the disinformation is published begins with MPR, very similar to the acronym for NPR public radio. This is a common strategy among sites broadcasting false content.


Aquest article és part del projecte "Les Mentides Amenacen la Salut", el primer portal de fact-checking de rumors sobre la covid-19 de Catalunya.

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