Real-world data from Israel suggests that COVID-19 vaccines will prevent transmission of the coronavirus, in addition to protecting against symptomatic disease.
The lack of clear data on transmission has meant that even people who are vaccinated must be careful around unvaccinated people, particularly those at risk for severe COVID-19 infections.
The preliminary information from Israel, where more than half the adults have been vaccinated, most with the Pfizer-BioNTech vaccine, showed those who received the vaccine did not develop symptoms or transmit the disease.
"It looks like 90% reduction in asymptomatic transmission. So that's really good," said Dr. Peter Hotez, dean of the National School of Tropical Medicine, at Baylor College of Medicine in Houston.
Practically speaking, that means the vaccine may enable people to produce antibodies that reduce virus levels in the nose and the mouth, making them less likely to be contagious, he said.
"That's really exciting news. If we can vaccinate a high proportion of the U.S. population, I do think we can halt virus transmission," Hotez said.
Although the study looked only at the Pfizer-BioNTech vaccine, Hotez said research in monkeys suggest that other vaccines likely would provide the same protections.
The results were released as a news release, adding to data published last month in The New England Journal of Medicine.
The data finally confirms what most scientists and health experts had suspected and hoped.
Based on this assumption, the Centers for Disease Control and Prevention released guidelines Monday for Americans who have been fully vaccinated, encouraging them to maintain precautions around unvaccinated high-risk people.
But people exposed to COVID-19 after being fully vaccinated – more than two weeks after a second shot of the Moderna or Pfizer-BioNTech vaccine, or the sole shot of Johnson & Johnson – don't need to quarantine or get a COVID-19 test, according to the guidelines.
Dr. Edgar Sanchez, infectious disease physician at Orlando Health in Florida said the CDC's assumption that vaccination will prevent transmission is sound.
“We’ve had to do a lot of things on incomplete data" during the pandemic, he said. "(But) we’re getting more and more data that vaccinations are dropping asymptomatic spread.”
CDC recommendations say fully immunized individuals can gather with other vaccinated people inside a home without wearing a mask or socially distancing. They can also gather with unvaccinated individuals with low risk of severe COVID-19 under the same circumstances.
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The CDC guidance – now supported by evidence from Israel – also helps to incentivize people to get vaccinated even though they may be discouraged by state restrictions and public health safety measures, Sanchez said.
“One of the things we found out is that a lot of people who are on the fence about vaccinating are starting to think, ‘If I can’t do anything, what’s the point of vaccinated?’” he said. “We can’t be so rigid that we hurt our chances of everybody getting vaccinated.”
More than 3.7 million people in Israel have received two shots of the Pfizer-BioNTech vaccine, out of a total population of about 9 million, and the country has begun to reopen its restaurants, bars, gyms and pools.
The data from Israel also showed Pfizer's vaccine was highly effective against the coronavirus variant first discovered in Britain, called B.1.1.7. The variant made up more than 80% of the specimens tested in the analysis. There weren’t enough infections with the variant B.1351, first discovered in South Africa, to determine whether the vaccine is effective against it.
In the analysis, the Pfizer-BioNTech vaccine was 97% effective in preventing symptomatic disease, severe disease and death, which tracks closely with results from late-stage trials conducted last fall.
“The findings which suggest that the vaccine may also provide protection against asymptomatic SARS-CoV-2 infections are particularly meaningful as we look to disrupt the spread of the virus around the globe," Luis Jodar, senior vice president and chief medical officer of Pfizer Vaccines, said in a prepared statement.
"Altogether, these data are critical to understanding the role of vaccination in combating the pandemic and provide hope to other countries dealing with this devastating disease”
Follow Adrianna Rodriguez on Twitter: @AdriannaUSAT.
Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.
This article originally appeared on USA TODAY: Pfizer COVID vaccine works against asymptomatic spread, data suggests