Pfizer COVID Vaccine: Scientists React with Caution and Questions

Scientists say Pfizer's announcement that its coronavirus vaccine is over 90 percent effective should be treated with caution. The news was announced via a press release and no data has been made available to substantiate the company's claims, raising questions about how effective it might actually be among the wider public.

The vaccine developed by Pfizer and BioNTech has been widely touted as one of the most promising candidates against COVID-19. Pfizer started the phase 3 clinical trial of the vaccine, known as BNT162b2, on July 27. It has so far enrolled over 43,500 people, almost 39,000 of which have had two doses of the vaccine.

In the press release, Pfizer said it will continue to enroll participants until the "final analysis," which will be when 164 COVID-19 cases have been confirmed among the cohort. So far 94 cases have been confirmed.

"The case split between vaccinated individuals and those who received the placebo indicates a vaccine efficacy rate above 90 percent, at seven days after the second dose," the statement from Pfizer said. This means that protection is achieved 28 days after the initiation of the vaccination, which consists of a two-dose schedule. As the study continues, the final vaccine efficacy percentage may vary."

The company said that together with BioNTech, it plans to submit data for peer review in a scientific publication once the full trial is completed. When this will be is not known.

Pfizer said it is expecting to produce up to 50 million doses of the vaccine by the end of the year, and 1.3 billion doses in 2021. But both experts and politicians have urged caution over the announcement.

President-elect Joe Biden issued a statement saying that while the results were "excellent news" and "cause for hope," the battle against coronavirus is far from over. "It will be many more months before there is widespread vaccination in this country," he said.

Scientists have said the news from Pfizer and BioNTech is very welcome, but that at present there is no evidence to support the claims of 90 percent efficacy.

"The full data set on which the claim is based has not yet been released and so we don't know exactly what has been found," Eleanor Riley, Professor of Immunology and Infectious Disease at the U.K.'s University of Edinburgh, said in a statement.

"The two companies are at pains to point out that the trial participants are ethnically diverse, which is good, but say nothing about the age of people in the trial. If a vaccine is to reduce severe disease and death, and thus enable the population at large to return to their normal day-to-day lives, it will need to be effective in older and elderly members of our society. We also know nothing yet about the severity of cases that were seen in the trial, whether infection or infectiousness was prevented, or how long the immunity is expected to last."

Michael Head, Senior Research Fellow in Global Health at the University of Southampton, U.K., also voiced concerns over the findings being made available in a press release, and said whether the vaccine is effective in the elderly will be key to its success—which, at present, is unclear.

Older people are known to be more likely to develop severe cases of COVID-19. There are around 40 million people in the U.S. above the age of 65. If a vaccine is ineffective on this group, its overall effectiveness is likely to fall.

The vaccine has also not been tested on pregnant women or children.

Head said there will also be major problems regarding distribution of the vaccine: "It has been reported that the vaccine requires storage at minus 70 degrees centigrade (-94 F), and that is not necessarily routinely available in most health centers even in the U.K., let alone globally."

Others pointed out that as two doses are required, the true effectiveness of the vaccine will not be known for some time. Needing two doses will also have an impact on vaccine production—meaning that Pfizer's claim of 50 million doses translates to 25 million people vaccinated.

Another major hurdle in distributing a vaccine, even if it turns out to be 90 percent effective, is getting people to take it. Surveys from the U.S. show willingness to have any vaccine against COVID-19 has fallen to around 50 percent.

Pfizer and BioNTech say they plan to apply to the U.S. Food and Drugs Administration for Emergency Use Authorization (EUA) in the third week of November.

Over the course of the pandemic, the use of EUAs to push through tests and treatments for COVID-19 has been widely criticized, with many health experts saying it has undermined public trust. The potential for an EUA to be used for a vaccine was met with even greater concern. In August, Dr. Anthony Fauci warned against their use before efficacy has been shown.

"One of the potential dangers if you prematurely let a vaccine out is that it would make it difficult, if not impossible, for the other vaccines to enrol people in their trial," he told Reuters. "To me, it's absolutely paramount that you definitively show that a vaccine is safe and effective."

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Stock image representing a vaccine. Scientists have urged caution about the announcement that Pfizer's vaccine is 90 percent effective against COVID-19. iStock