The study, which was published in the New England Journal of Medicine, analyzed electronic health records of military veterans who received the Moderna and Pfizer-BioNTech vaccines.
Overall, researchers found that both vaccines were very effective at preventing COVID-19, along with hospitalization and death. But the Moderna vaccine had a slight edge.
The study specifically looked at data from two groups with 219,842 people, with a 24-week follow-up period. During that time, the Alpha variant was the most common COVID-19 variant circulating. (Now, the Delta variant makes up more than 99.9% of COVID-19 cases in the U.S.)
The researchers found that there was an estimated risk of 4.52 documented infections per 1,000 people in the Moderna vaccine group and 5.74 per 1,000 in the Pfizer-BioNTech group. There were also slightly higher numbers across the board for the Pfizer-BioNTech group in symptomatic infections, hospitalization, and deaths. But the numbers are small.
While the main portion of the study was conducted when Alpha was the dominant strain, the researchers found that Moderna also had better efficacy during an additional research phase when Delta was the main circulating strain.
“Both vaccines are incredibly effective, with only rare breakthrough cases,” study co-author J.P. Casas, MD, PhD, an associate professor at Harvard Medical School, said in a statement. “But regardless of the predominant strain—Alpha earlier and then Delta later—Moderna was shown to be slightly more effective.”
But infectious disease experts say that people who had the Pfizer-BioNTech vaccine shouldn’t panic and assume they’re no longer protected. The differences between effectiveness are minor.
“There is strong evidence that the Pfizer vaccine is still very protective,” Richard Watkins, MD, an infectious disease physician and professor of internal medicine at the Northeast Ohio Medical University, told Verywell.
What Previous Data Shows
Previous data on the COVID-19 vaccines has found slightly different numbers. Here’s what the original efficacy data on each vaccine was:
Pfizer-BioNTech: 95% Moderna: 94. 1% Johnson & Johnson: 66. 3%
However, data has shown that vaccine efficacy wanes over time.
The Centers for Disease Control and Prevention (CDC) now recommends that all adults aged 18 and older get a COVID-19 booster shot. People who received the Moderna or Pfizer-BioNTech vaccines should get a booster six months after completing their original vaccination series, and those who received the Johnson & Johnson vaccine should get a booster two months after completing their vaccination series.
Both Vaccines Are Highly Effective
Amesh A. Adalja, MD, infectious disease expert and a senior scholar at the Johns Hopkins Center for Health Security, emphasizes that both vaccines are crucial tools for curbing the pandemic.
“Both vaccines are extremely good at protecting against what matters—serious disease,” he told Verywell. “It’s difficult to make head-to-head comparisons because the Moderna vaccine is a higher dose than Pfizer and the doses are spaced further apart, which may explain higher efficacy seen.”
While the percentages sound like there is a big difference between the two, Thomas Russo, MD, professor and chief of infectious disease at the University at Buffalo in New York, told Verywell that they are “deceiving,” noting that the actual numbers show these vaccines perform similarly well.
“The number of hospitalizations and infections per 1,000 people are extraordinarily low with both vaccines,” he said. “The data show how well they work.” And, Russo added, “booster shots will further augment the protection.”
Reynold Panettieri, MD, vice chancellor for translational medicine and science at Rutgers University, told Verywell that people should “absolutely not” think that one mRNA vaccine is better than the other. “The data show that both mRNA vaccines are incredibly successful at decreasing infection,” he said.
Panettieri said that, as of now, “the greatest risk to people with COVID-19 is being unvaccinated, and the second greatest risk is not getting the booster.”
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.
