On Monday, March 29, 2021, the Centers for Disease Control and Prevention (CDC) released data from a study conducted on nearly 4,000 vaccinated health care workers. Results from the study showed that a single dose of the Pfizer or Moderna vaccine was 80% effective in preventing infections, which jumped to 90% following the second dose. These findings serve as a major reassurance in the efficacy of mRNA vaccines, as millions of doses of the vaccines are expected to be available in the coming months.
The CDC stated that “These findings indicate that authorized mRNA COVID-19 vaccines are effective for preventing SARS-CoV-2 infection, regardless of symptom status, among working-age adults in real-world conditions.”
The study was conducted on a group of 3,950 healthcare professionals, first responders, and essential frontline workers, all of whom had no previous documentation of COVID-19 infection, and was tested via nasal swabs every week between December 14 and March 13.
Of the nearly 4,000 individuals that were included in the study, 2,479 (62.8%) received both recommended doses, and 477 (12.1%) received only one. The infection rate among participants who were vaccinated was just 0.04, compared with 1.38 among the unvaccinated participants.
In the 14 days following the initial dose, the vaccine displayed an effectiveness of around 80% in preventing COVID-19, which could prove to boost arguments made by some healthcare experts that argue the United States should prioritize giving all Americans one dose of a vaccine before moving on the second, which could help raise immunity levels.
While these findings are promising, experts warn against the ‘good enough’ mindset seen by many who have received their first round of vaccination. Dr.Anthony Fauci, White House chief medical advisor and leading expert on infectious disease, has echoed these concerns in previous White House Briefings, stating that individuals should all receive both doses, regardless of data showing their effectiveness in single doses.
In a response to the study, CDC director Director Dr. Rochelle Walensky stated, “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.”
Real-world data such as that provided by the CDC is key in the continuing support needed surrounding the nationwide vaccination of Americans. As of Monday, over 95 million Americans (28.6%) have received at least one dose of an approved vaccine, with roughly 52 million (15.8%) being fully vaccinated.