A study of healthcare and other essential workers provides strong evidence that messenger, or mRNA, vaccines, are 90% effective against COVID-19, according to the Centers for Disease Control and Prevention. But case rates are increasing again, pitting the pace of vaccinations against the effects of spreading virus variants, observers say.
The agency’s latest investigation followed almost 4,000 participants in six states after they received either the Pfizer-BioNTech or Moderna mRNA vaccines. Risk of infection dropped by 90% two or more weeks after the second dose, the researchers found.
The findings demonstrate that U.S. vaccination efforts are having a substantial preventive effect among working-age adults, the agency said. They also bolster the CDC’s recommendation for getting the full two-dose immunization with mRNA vaccines, it added. A third federally approved vaccine, from Johnson & Johnson, uses a different technology and was not included in the study. It has been shown to be 67% effective overall in preventing moderate to severe/critical COVID-19, and 100% protective against ICU admission and death.
More vaccinations needed to combat variants
In the meantime, U.S. COVID-19 case rates have begun to increase again for the first time since January, the agency said. In a Monday press briefing, CDC Director Rochelle Walensky, M.D., pleaded with Americans not to let down their guard, according to the Associated Press.
Cases were up 10% last week from the previous week, and hospitalizations and deaths are rising as well, the news outlet reported.
Experts say the increase in cases may be related to new genetic variants of SARS-CoV-2, the virus that causes the COVID-19. What the CDC calls “variants of concern” have mutated to spread more easily and to possibly cause more severe disease, according to a report by NPR. Now they are making inroads nationwide and becoming the dominant strains of the virus in many places.
One expert has called the new circumstances a race between vaccinations and variants, tweeting that the variants have recently “pulled ahead” of the pace of U.S. vaccination. “Holding tight until more folks vaccinated [is the] key to winning this race,” tweeted Ashish Jha, M.D., MPH, a public health policy researcher from Brown University’s School of Public Health.
“We are not powerless; we can change this trajectory of the pandemic,” the CDC’s Walensky said, according to NPR. She and the White House’s chief medical adviser, Anthony Fauci, M.D., have asked Americans to continue maintaining social distancing measures and mask wearing.
