On Monday, pharmaceutical company Pfizer announced that its experimental vaccine against the coronavirus that causes covid-19 was shown to be highly effective in an early analysis of its ongoing Phase 3 clinical trial. The data underlying these results has yet to be verified by outside scientists and is preliminary, however, so while this is encouraging news, we’re still in the realm of cautious optimism.
According to Pfizer, the analysis was conducted by the independent group of scientists brought on to monitor the data and any safety concerns of the clinical trial, which is a common practice. These scientists began their analysis at a point when there had been 94 confirmed cases of covid-19 shared between the two groups of volunteers, who received either two doses of a vaccine or placebo. Based on the rates of infection between each group, the analysis estimated that Pfizer’s vaccine was more than 90% effective at preventing covid-19.
“Today is a great day for science and humanity. The first set of results from our Phase 3 COVID-19 vaccine trial provides the initial evidence of our vaccine’s ability to prevent COVID-19,” said Albert Bourla, Pfizer chairman and CEO, in the company’s announcement.
Pfizer, in collaboration with German company BioNTech, was one of the first to enter the race to find a vaccine for covid-19, and the approach—a messenger RNA (mRNA) vaccine—was thought to give them a head start in development. mRNA is routinely used by the body’s cells to help create the proteins their DNA instructs them to make. However, mRNA vaccines use their own lab-created mRNA to program the body’s cells to produce a protein, or antigen, that matches something found in the target germ; in this case, that’s the coronavirus known as SARS-CoV-2. The body’s immune system, it’s hoped, will recognize the dummy package as the sign of an infection and respond accordingly, along the way learning to beat the real thing if it ever shows up. Though mRNA vaccines are considered a promising technology for vaccine development, since the basic model can be quickly customized to fit different pathogens, no such vaccine has yet to win regulatory approval.
Unlike several other companies, Pfizer chose not to work directly with the U.S. federal government on the research and development of its vaccine, though it did later enter into a contract with the government that would provide funding for 100 million doses of a vaccine if it turned out to be successful.
In its announcement, Pfizer also revealed that its talks with the FDA led it to postpone releasing an interim analysis when data from only 32 confirmed cases of covid-19 was available. Despite the minor delay, scientists have still warned against reading too much into the results presented Monday, especially since the data hasn’t been made public, either in a peer-reviewed journal or in a preprint paper. This “science-by-press release” means that it’s impossible to know the details of Pfizer’s early data (such as exactly how many volunteers were studied in this analysis) and any possible caveats they might carry.
President-elect Joe Biden was among many to strike a note of caution on the news, stating that he had been informed of the results last night.
“I congratulate the brilliant women and men who helped produce this breakthrough and to give us such cause for hope,” Biden said in a statement. “At the same time, it is also important to understand that the end of the battle against covid-19 is still months away.... Americans will have to rely on masking, distancing, contact tracing, hand washing, and other measures to keep themselves safe well into next year. Today’s news is great news, but it doesn’t change that fact.”
Indeed, it will take more time for the full results for Pfizer’s trial, now involving 42,000 people, to be analyzed. And even if the company decides to apply for an emergency use authorization, the data needed to petition for that designation would only be available by late November at the earliest, according to the company. Experts have repeatedly said that it will take until sometime next year for any successful vaccine to become widely available to the public. Pfizer in particular would have to address additional supply and distribution issues, since its vaccine needs to be stored at very cold temperatures.
All of these important questions aside, the early results are definitely a spot of good news in a year that has been far short of them. And should the results hold up, they could also provide more optimism about other vaccines in development, since many are focusing on the same protein targets found on the coronavirus. Here’s hoping.