A real-world study in Duluth and seven other sites found the Pfizer and Moderna COVID-19 vaccines are 90% effective in preventing the disease.
The federal Centers for Disease Control and Prevention (CDC) study, results of which were released on Monday, looked at the vaccines' effectiveness in preventing infection among healthcare personnel, first responders and other essential and frontline workers.
Clinical trials of the vaccines prior to getting emergency use authorization in the U.S. only looked at how effective the vaccines were at preventing symptomatic infections, which they were found to be 90% effective.
But this study confirms the vaccines protect against asymptomatic infections, especially among healthcare workers who are more likely to be exposed to the disease.
"It protects against asymptomatic infections as well," Dr. Harmony Tyner, an infectious disease specialist at St. Luke's Regional Health Care System in Duluth and a co-author of the study said, according to the Star Tribune. "We know it kept people alive, we know it kept people from dying, but [the clinical trials] didn't test against asymptomatic infections, which is huge."
The vaccines' effectiveness in preventing the virus was studied in Duluth, as well as Phoenix, Tucson, and other areas in Arizona; Miami, Florida; Portland, Oregon; Temple, Texas; and Salt Lake City, Utah, from Dec. 14, 2020, to March 13, 2021, the CDC's study shows.
The study involved about 3,950 people (448 in Duluth), with the CDC finding the vaccines reduced the risk of infection by 80% after the first dose and 90% after the second dose.
The study's findings:
- Among the 2,479 people who were fully vaccinated, there were just three confirmed infections.
- Among the 477 people who got one dose, eight infections were reported.
- Among the 994 people who were not vaccinated, 161 developed infections.
- No deaths were reported.
“This study shows that our national vaccination efforts are working. The authorized mRNA COVID-19 vaccines provided early, substantial real-world protection against infection for our nation’s health care personnel, first responders, and other frontline essential workers,” CDC Director Rochelle P. Walensky, MD, MPH said in a statement.
“These findings should offer hope to the millions of Americans receiving COVID-19 vaccines each day and to those who will have the opportunity to roll up their sleeves and get vaccinated in the weeks ahead. The authorized vaccines are the key tool that will help bring an end to this devastating pandemic.”
The results of the study are consistent with other trials and studies in other countries, including in Israel and the United Kingdom, the Washington Post reports.