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Pfizer Vaccine Highly Effective at Preventing COVID-19 Transmission, Study Shows

Vials labeled "COVID-19 vaccine" on a blurred lab-like background.

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Key Takeaways

  • Pfizer announced that its COVID-19 vaccine can help prevent the spread of the SARS-CoV-2 virus.
  • Research has shown that the vaccine is 94% effective at preventing the spread of COVID-19.
  • Doctors say that it’s likely the other COVID-19 vaccines authorized for use in the U.S. will have similar results.

Data suggest that the Pfizer-BioNTech vaccine is highly effective at preventing the spread of COVID-19 in people who are fully vaccinated against the virus.

On March 11, 2021, Pfizer made the announcement that its mRNA vaccine for COVID-19 was 94% effective at preventing the asymptomatic transmission of SARS-CoV-2, the virus that causes COVID-19.

The findings were taken from de-identified patient data in Israel. The data was collected between January 17 and March 6, 2021—during which time the Pfizer-BioNTech vaccine was the only COVID-19 vaccine available in the country. It's also worth noting that at the time, the predominant strain of the virus was B.1.1.7, the U.K. variant of SARS-CoV-2.

The data showed that the vaccine was at least 97% effective against symptomatic cases of COVID-19, hospitalizations, severe and critical hospitalizations, and deaths.

In a press release, Professor Yeheskel Levy, the director of the Israel Ministry of Health, said, “This clearly demonstrates the power of the COVID-19 vaccine to fight this virus and encourages us to continue even more intensively with our vaccination campaign. We aim to achieve even higher uptake in people of all ages, which gives us hope of regaining normal economic and social function in the not so distant future.”

Luis Jodar, PhD, senior vice president and chief medical officer of Pfizer Vaccines, added in the release that the company is “extremely encouraged” by the findings.

Many medical professionals on the frontlines of the COVID-19 pandemic are encouraged by the findings. “This is great news,” Richard Watkins, MD, an infectious disease specialist and a professor of internal medicine at the Northeast Ohio Medical University, tells Verywell.

“We knew that the Pfizer vaccine was great at preventing disease and death, but we didn’t know whether it would preventing transmission of the virus,” Timothy Murphy, MD, senior associate dean for clinical and translational research at the University at Buffalo Jacobs School of Medicine and Biomedical Sciences, tells Verywell.

What about the Other COVID-19 Vaccines?

Murphy says that the findings are “not surprising” but that “it’s important to have the data." The next question is: Will the same hold true for other vaccines authorized in the United States?

Watkins says that it’s a “reasonable assumption” that the Moderna and Johnson & Johnson vaccines will also prevent transmission of the virus. However, he adds that “further studies are needed to test that hypothesis.” 

Murphy agrees but says that he's "more confident saying that" the Moderna vaccine will have similar results because it's also an mRNA vaccine like the Pfizer-BioNTech vaccine.

That said, even the most effective vaccine is only going to work if people get it. For now, the goal is simply getting shots into more arms. "Hopefully, widespread vaccination will be the tipping point that leads to the end of the pandemic," Watkins says.

What This Means For You

Data show that the Pfizer-BioNTech vaccine helps prevent the spread of COVID-19, dramatically lowering the risk that people fully vaccinated against the virus will make others sick.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

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  1. Pfizer. Real-world evidence confirms high effectiveness of Pfizer-BioNTech COVID-19 vaccine and profound public health impact of vaccination one year after pandemic declared. Published March 11, 2021.