One shot of either the Pfizer
While both vaccines require two doses to reach their full effectiveness, CDC researchers found that high levels of antibodies were present in an individual just two weeks after the first dose. The study also found that the vaccine's effectiveness rose to 90% two weeks after the second dose.
As a result, people are considered "partially vaccinated" two weeks after their first dose of a mRNA vaccine and "fully vaccinated" two week after their second dose, according to CDC researchers. The study also demonstrates that both mRNA vaccines can reduce the risk of all COVID-19 infections, including asymptomatic.
The CDC drew data from 3,940 vaccinated health care personnel, first responders and other frontline essential workers from Dec. 14 through March 13. For the study, participants would take self-collected nasal swabs for diagnostic testing each week regardless of whether they developed symptoms of COVID-19 infection. Those participating in the study had no previous documented cases of COVID-19 infection.
Among the 3,950 participants in the study, about 63% received both recommended doses of an mRNA vaccine, while about 12% only received one dose. The infection rate among participants who were vaccinated was 0.04, compared with 1.38 for those who were not vaccinated, according to the CDC.
"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," said CDC Director Dr. Rochelle Walensky, 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 new CDC findings could lead to global public health officials wanting to prioritize giving world populations just one dose of a mRNA vaccine and delaying the second dose to further accelerate the global vaccination rate. Many, including the World Health Organization, have criticised the vaccine rollouts of wealthy nations like the United States, which has prioritized vaccinating its entire population before giving vaccines to other countries.
