Pfizer, Moderna Vaccines Effective Against Symptomatic, Asymptomatic Covid-19 Infection: CDC Study

By CodeBlue | 30 March 2021

The CDC real-world study on nearly 4,000 frontline workers and health care personnel in the US showed 80% effectiveness against Covid-19 after one dose of mRNA vaccine, and 90% protection after two doses.

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KUALA LUMPUR, March 30 — A new US real-world study showed that mRNA vaccines are 90 per cent effective in preventing any Covid-19 infection, including asymptomatic cases.

The study by the United States’ Centers for Disease Control and Prevention (CDC) among 3,950 individuals — consisting mostly of health care workers and frontline personnel — showed that the risk of Covid-19 infection was reduced by 80 per cent in two or more weeks after participants received their first jab with either the Pfizer-BioNTech or Moderna vaccine.

STAT reported that this estimate, however, only applied to the brief period before the second dose was administered, as the study was not designed to test how well the vaccine works if one does not receive the second dose. Inoculated participants in the CDC study took the recommended two doses of the vaccine regimen.

Protection against Covid-19 infection increased to 90 per cent two weeks after participants received their second dose of the mRNA vaccine to complete inoculation.

“This is important because preventing both asymptomatic and pre-symptomatic infections among health care workers and other essential workers through vaccination can help prevent the spread of SARS-CoV-2 to those they care for or serve,” the CDC was quoted as saying.

The CDC stated that the effectiveness in reducing the risk of virus transmission is essential, especially among asymptomatic individuals or individuals who only show symptoms several days after infection, particularly health care and front line workers. 

These are the individuals who are often in close contact with patients and have a high probability to transmit the coronavirus to others. 

“These findings also underscore the importance of getting both of the recommended doses of the vaccine in order to get the greatest level of protection against Covid-19, especially as our concerns about variants escalate” CNN quoted CDC Director Dr Rochelle Walensky as saying. 

Dr Walensky also mentioned that the US’ Covid-19 vaccination mission has started to work well. CDC stated that its research was one of the pioneer studies to look at the efficacy of mRNA vaccines after the US started giving jabs to the public in December last year.

As of yesterday, the US has administered more than 142 million doses of the Moderna and Pfizer-BioNTech vaccines, according to the CDC, and more than 49 million Americans have undergone complete vaccination with the mRNA shots.

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