The coronavirus vaccines from Moderna and Pfizer-BioNTech are highly effective at preventing sickness, a new real-world study among health care workers confirms.
The two-dose vaccines reduced the risk of getting sick with COVID-19 symptoms by 94% among those who were fully vaccinated and by 82% among those who were partially vaccinated, the study found, according to the Centers for Disease Control and Prevention.
“This report provided the most compelling information to date that COVID-19 vaccines were performing as expected in the real world,” said CDC Director Dr. Rochelle Walensky in a statement. “This study, added to the many studies that preceded it, was pivotal to CDC changing its recommendations for those who are fully vaccinated against COVID-19.”
The study pulled data from a network that includes more than 500,000 health care workers across 33 sites in 25 states. It compared the vaccination status of participants who tested positive for COVID-19 with the vaccination status of those who tested negative, known as “controls.”
Of 1,843 study participants, there were 623 cases and 1,220 controls. Case-patients were identified as those who tested positive for SARS-CoV-2, the virus that causes COVID-19 disease, and who had at least one symptom. Control participants were those who tested negative, regardless of symptoms. Some participants in both groups had received a COVID-19 vaccine dose.
Researchers then calculated vaccine effectiveness by comparing the odds of COVID-19 vaccination in cases and controls.
They found that only 2% of case-patients and 1% of control participants required hospitalization for severe illness. No deaths occurred in either group.
Case-patients were also much more likely than control participants to experience symptoms associated with COVID-19 such as fever (40% versus 23%), cough (56% versus 22%), or shortness of breath (26% versus 7%). Only 5% of case-patients and 14% of control participants reported having only mild symptoms such as sore throat and headache.
Three-quarters of the health care staff enrolled in the study worked at acute care hospitals while 25% worked in outpatient or specialty clinics. The median age was 38 years.
This week, federal regulators granted emergency use authorization for the use of the Pfizer COVID-19 vaccine for adolescents 12 to 15 years old. The vaccine is also approved for those 16 years and older. The Moderna vaccine is approved for use in adults 18 years and older.