Syringe containers for the Covid-19 vaccines from Pfizer BioNtech and Moderna Inc. in Tucson, Arizona, USA, on Friday, January 15, 2021.

Cherry Orr | Bloomberg | Getty Images

A single dose of Pfizer or Moderna’s Covid-19 vaccines was 80% effective in preventing coronavirus infections, according to a new study by the Centers for Disease Control and Prevention of vaccinated healthcare workers.

The effectiveness of the partial immunization was noted two weeks after the first dose, which examined nearly 4,000 health care workers, first responders and frontline workers between December 14 and March 13, according to the CDC, which was released on Monday, had no prior laboratory documentation 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.

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.

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