A single dose of Pfizeror Moderna‘s Covid-19 According to a new study by the Centers for Disease Control and Prevention of vaccinated health care workers, the vaccine was 80% effective in preventing coronavirus infections.
The effectiveness of the partial immunization was noted two weeks after the first dose, according to the CDC, which studied nearly 4,000 health care workers, first responders and frontline workers between December 14 and March 13, according to other key study staff, which began on Monday had no prior laboratory documentation of the Covid-19 infection.
Two doses are better than one, federal health officials said, adding that the vaccines’ effectiveness rose to 90% two weeks after the second dose.
“These results show that approved mRNA-COVID-19 vaccines in adults of working age effectively prevent SARS-CoV-2 infection under real conditions, regardless of symptom status,” wrote the US agency in the study. “The COVID-19 vaccination is recommended to all entitled persons.”
The new CDC results should back up arguments by some health experts and health officials that the US should give Americans only one dose of vaccines as a priority before moving on to a second dose, accelerating the pace of vaccination across the country.
The CDC results were released just minutes before the agency’s director. Dr. Rochelle Walensky told reporters during a press conference that the US is facing “impending doom” as daily Covid-19 cases begin to recoverand threatens to send more people to hospital, although vaccinations increase across the country.
Unlike the Johnson & Johnson vaccine, which requires one dose, the Pfizer and Moderna vaccines require two vaccinations three to four weeks apart. The Chief Medical Officer of the White House, Dr. Anthony Fauci, has said repeatedly over the past few months that the US should stick to the two-dose regime.
Dr. Paul Offit, a voting member of the FDA’s Advisory Committee on Vaccines and Related Biological Products who reviewed both Pfizer’s and Moderna’s vaccines for emergency approval, said the CDC study was overall “good news” .
However, he said he feared people would now think a dose of the vaccines was “good enough” and would not return for a second shot. He said studies have shown that immunity actually appears to be “more permanent” after the second dose, meaning protection may last longer.
“The reason these are two-dose vaccines is because the second dose provides a titer of neutralizing antibodies, virus-specific neutralizing antibodies, that is nearly ten times greater than the first dose,” he told CNBC. Neutralizing antibodies play an important role in the defense of cells against the virus.
Second, and more importantly, scientists have also discovered what are known as T cells, another important part of the immune response that usually lasts longer Immunity, he said.
There are also still questions about the highly contagious variants and whether the vaccines protect mild to moderate forms of the disease, he said.
Of the 3,950 participants in the study, 2,479, or 62.8%, received both recommended doses, and 477, or 12.1%, received only one dose, according to the CDC. The infection rate among the vaccinated participants was 0.04 compared to 1.38 among the non-vaccinated participants.
The study was conducted in eight locations in the United States: Phoenix, Tucson, and other areas in Arizona; Miami, Florida; Duluth, Minnesota; Portland, Oregon; Temple, Texas; and Salt Lake City, Utah. The majority of the participants were female, white, and had no chronic illnesses, according to the CDC.
The study had limitations, the CDC said, adding that delays in deliveries could reduce virus detection sensitivity of Covid-19 tests.
Preliminary real-world vaccine efficacy results for both vaccines complement and expand on estimates of vaccine efficacy from other recent studies, the CDC said. A large study published in the New England Journal of Medicine in February found Pfizer’s vaccine 94% protected against symptomatic Covid.