Pfizer's COVID-19 Vaccine Has 90% Efficacy Rate, Preliminary Data Shows


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On Friday, November 20, Pfizer and BioNTech filed for emergency use authorization from the U.S. Food and Drug Administration (FDA) after collecting the necessary safety data. Pfizer and BioNTech are the first companies to file for an emergency use authorization for their COVID-19 vaccine.

The companies say filing for this application will "potentially enable use of the vaccine in high-risk populations in the U.S. by the middle to end of December 2020," according to a press release.

On November 18, the companies announced their final Phase 3 trial data showing their COVID-19 vaccine is 95% effective and had no serious side effects. The FDA required manufacturers to follow at least half of the people who received a vaccine in their Phase 3 clinical trials for two months, in order to ensure some safety data exists before the vaccine is considered for use. 

The FDA will now review the application, as will the independent Vaccines and Related Biological Products Advisory Committee. It’s not yet known how long that process will take.

Pfizer and BioNTech announced Monday that preliminary data shows their vaccine has a 90% efficacy against COVID-19 in those without evidence of prior infection. It’s the first vaccine candidate tested in the U.S. to go on to generate late-stage data.

The vaccine, BNT162b2, is still in Phase 3 of trials and the news was reported in a press release. Final results have not yet been published in a medical journal.

“The case split between vaccinated individuals and those who received the placebo indicates a vaccine efficacy rate above 90% at seven days after the second dose. This means that protection is achieved 28 days after the initiation of the vaccination, which consists of a two-dose schedule,” Pfizer says in a statement.

The data was evaluated by an independent data monitoring committee (DMC) on November 8. Having an outside review is standard for clinical trials, notes Amesh Adalja, MD, an assistant professor at Johns Hopkins Bloomberg School of Public Health.

Promising COVID-19 Vaccine News

Adalja tells Verywell he wouldn’t be surprised if larger sample sizes cause the efficacy to drop in the future, but he doesn’t think it will go below 20%.

“This is good news, but it’s still a significant time period before vaccine distribution is accomplished,” he says.

Adalja warns that people still need to take protective measures. “This vaccine won’t impact the tough winter season we face,” he says.

Maria Elena Bottazzi, PhD, associate dean at the National School of Tropical Medicine at Baylor University, calls the news an important achievement as it may help us understand the results coming from vaccines in Phase 3 clinical trials.

“However, remember these Phase 3 trials will not say anything about levels of efficacy needed to achieve what eventually we really need: herd immunity or protection in large numbers of the global population,” Bottazzi says.

She admits it was hard to tell much not having seen the data and going off a company press release. It’s not clear if the vaccine protects against mild and severe illness. We don’t know about the durability of protection, and if the vaccine stops virus shedding and transmission. Access questions remain as well, she adds.

What This Means For You

The clinical trial is not completed and the vaccine isn't out yet, but experts say the efficacy rate so far is promising.

Vaccine Efficacy vs. Vaccine Effectiveness

Vaccine efficacy and vaccine effectiveness are terms used to gauge the proportionate decrease in cases of people who are vaccinated. Efficacy is used during clinical trials, while effectiveness refers to how effective a vaccine is when rolled out.

Because the clinical trial is still occurring, the 90% efficacy figure could differ when the trial is complete and the report finalized. Pfizer and BioNTech says they will submit Phase 3 trial data to a scientific peer-reviewed publication.

The DMC has not reported any serious safety concerns with the vaccine. They endorse continuing the study to collect more data. That will then be discussed with “regulatory authorities” worldwide, Pfizer says.

The Phase 3 clinical trial of BNT162b2 started at the end of July. It involves 43,538 people; 38,955 received a second dose of the vaccine as of November 8. The trial is still enrolling people and will continue when there have been a total of 164 confirmed COVID-19 cases.

The trial is expected to look at whether the vaccine can prevent people from getting COVID-19 if they’ve had SARS-CoV-2 and assess if it prevents against severe COVID-19.

A Step Forward for mRNA Technology

Pfizer and BioNTech's BNT162b2 vaccine is a messenger RNA (mRNA) vaccine.

A vaccine using mRNA technology hasn’t yet been approved for any infectious disease. Gene-based vaccines such as DNA and mRNA vaccines trigger cells to transform genetic material into proteins, which produces an immune response. The technology enables vaccines to be developed more quickly.

Similar vaccines are also part of ongoing clinical trials, Adalja says. Moderna's vaccine uses mRNA technology.

Pfizer and BioNTech's preliminary outcomes are good because it gives us data on mRNA vaccine efficacy. The technology wasn’t available a decade ago, Adalja adds.

Is the Vaccine Part of Operation Warp Speed?

Pfizer and BioNTech expect to produce up to 50 million vaccine doses this year, and up to 1.3 billion doses in 2021.

Pfizer plans to seek emergency use authorization from the Food and Drug Administration (FDA) later this month, The New York Times reported. That would help distribute the vaccine faster than normal.

Kathrin Jansen, a senior vice president and the head of vaccine research and development at Pfizer, told the paper that Pfizer did not take any federal money to fund vaccine research and development. She said they were “never part of the Warp Speed.” Operation Warp Speed is the U.S. government’s initiative to roll out COVID-19 vaccines.

Jansen told The New York Times that Pfizer never took “any money from the U.S. government, or from anyone.”

However, a U.S. Department of Health and Human Services (HHS) and the Department of Defense (DoD) press release from July announced an agreement with the drug company for a COVID-19 vaccine.

Similarly, a July Pfizer press release states the company has an agreement with HHS and DoD “to meet the Operation Warp Speed program goal to begin delivering 300 million doses of a vaccine for COVID-19 in 2021.” According to the release, the U.S. government will pay the companies $1.95 billion after getting the first 100 million doses. The U.S. government also can acquire up to an additional 500 million doses, the release stated.

A representative from Pfizer tells Verywell that the company will sell vaccines to the government, but did not fund research and development activities.

Russia Claims Effective Vaccine Too

The news comes as Russia reports its Sputnik V vaccine was more than 90% effective. A Reuters article states the health ministry reported on the vaccine using data on actual vaccinations and not from a clinical trial.

“We have very little data on the Russian vaccine so it’s impossible to know what they actually have produced,” Adalja says.

As for the Russian vaccine, Bottazzi says people may be able to get it and take a booster later, even if it isn’t the best one.

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  1. U.S. National Library of Medicine. A Trial Investigating the Safety and Effects of One BNT162 Vaccine Against COVID-19 in Healthy Adults

  2. Leitner WW, et al. DNA and RNA-based vaccines: principles, progress and prospectsVaccine. 1999. doi:10.1016/s0264-410x(99)00271-6

  3. U.S. Department of Health and Human Services. U.S. Government Engages Pfizer to Produce Millions of Doses of COVID-19 Vaccine. July 22, 2020.

  4. Pfizer. Pfizer and BioNTech announce an agreement with U.S. government for up to 600 million doses of mRNA-based vaccine candidate against SARS-CoV-2. July 22, 2020.

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