A medical worker vaccinates a patient with a dose of the Moderna COVID-19 vaccine in the rooms of the Claudia Comte exhibition at the Museum of Contemporary Art "Castello di Rivoli" near Turin, Italy on May 27, 2021Share on Pinterest
A medical worker vaccinates a patient with a dose of the Moderna COVID-19 vaccine in the rooms of the Claudia Comte exhibition at the Museum of Contemporary Art “Castello di Rivoli” near Turin, Italy on May 27, 2021. MARCO BERTORELLO/Getty Images
  • According to a new analysis by the Centers for Disease Control and Prevention (CDC), COVID-19 mRNA vaccines reduce infection risk by 91% after two doses and 81% after one dose.
  • The study also concludes that those who do have a SARS-CoV-2 infection experience more mild illness.
  • Similarly, the few that do develop COVID-19 are sick for less time.

In a new press release, the Centers for Disease Control and Prevention (CDC) outline the latest findings from the so-called HEROES-RECOVER study.

The study is one of the first to demonstrate that the Pfizer-BioNTech and Moderna vaccines benefit people who get COVID-19 despite receiving full or partial vaccinations.

The HEROES-RECOVER study includes data from individuals who have increased potential exposure to SARS-CoV-2, including healthcare workers, frontline workers, and first responders.

Stay informed with live updates on the current COVID-19 outbreak and visit our coronavirus hub for more advice on prevention and treatment.

The researchers released preliminary results from the HEROES-RECOVER study in March 2021. At that time, they concluded that “[a]uthorized mRNA COVID-19 vaccines are effective for preventing SARS-CoV-2 infection in real-world conditions.”

Following the initial analysis, the CDC continued to capture data. The latest press release draws upon an additional 4 weeks of data.

The latest analysis uses data from 3,975 participants in eight regions of the United States. Each person received testing for SARS-CoV-2 infection once each week for 17 weeks, from December 13, 2020, to April 10, 2021.

The researchers screened positive tests further to assess viral load. They also measured how long the participants tested positive for SARS-CoV-2 to determine the rate of viral shedding.

During the analysis, the scientists considered other factors that might influence the results, including how often participants used personal protective equipment at work and in the community and the circulation of SARS-CoV-2 in their local area.

Overall, the scientists concluded:

“Once fully vaccinated, participants’ risk of infection was reduced by 91%. After partial vaccination, participants’ risk of infection was reduced by 81%. These estimates included symptomatic and asymptomatic infections.”

To understand how vaccination influenced the course of a SARS-CoV-2 infection, the scientists compared those who developed the viral infection despite vaccination with those who had the virus but had not received vaccination.

This analysis demonstrated that individuals who received partial or full vaccination and developed COVID-19 were sick for 6 fewer days and spent 2 fewer days in bed than those who developed COVID-19 and had not received vaccination.

Similarly, those vaccinated were roughly 60% less likely to develop symptoms, such as fever or chills, than those who were not.

Their findings also suggest that people who develop COVID-19 and are fully or partially vaccinated might be less likely to transmit the virus to others.

This, as the press release explains, is because “fully or partially vaccinated study participants had 40% less detectable virus in their nose […], and the virus was detected for 6 fewer days […] compared [with] those who were unvaccinated when [acquiring the infection].”

The scientists also showed that those who received partial or full vaccination had the virus for a shorter time. Those vaccinated were 66% less likely to have a positive test result for more than 1 week than unvaccinated people with a SARS-CoV-2 infection.

As the press release explains, “While these indicators are not a direct measure of a person’s ability to spread the virus, they [have correlations] with a reduced spread of other viruses, such as varicella and influenza.”

Overall, the findings add real-world evidence that COVID-19 vaccines are the best way to lower the number of COVID-19 cases, minimize severe illness, and stop the spread. The press release ends by noting:

”[T]he study findings support CDC’s recommendation to get fully vaccinated against COVID-19 as soon as you can. Everyone 12 years and older is now eligible to get a COVID-19 vaccination in the U.S.”

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