Pfizer and Moderna COVID-19 vaccines highly effective after first injection in real world, US study finds

(Reuters) – COVID-19 vaccines developed by Pfizer Inc with BioNTech SE and Moderna Inc reduced the risk of infection by 80% two weeks or more after the first of two injections, according to data from a US study released on Monday .

The risk of infection dropped 90% two weeks after the second shot, according to the study of nearly 4,000 U.S. health care workers and first responders.

The results validate previous studies which indicated that vaccines start working soon after a first dose and confirm that they also prevent asymptomatic infections.

Some countries facing limited vaccine supplies have pushed back second-dose schedules in hopes of providing some protection to more people. U.S. public health officials, however, continue to recommend that two doses be given according to the schedule allowed by regulators based on clinical trials.

The U.S. Centers for Disease Control and Prevention (CDC) study assessed the ability of vaccines to protect against infections, including infections that did not cause symptoms. Previous clinical trials conducted by the companies have evaluated the effectiveness of their vaccine in preventing illness due to COVID-19, but those studies have reportedly missed asymptomatic infections.

The results of the real-world use of these messenger RNA (mRNA) vaccines also confirm the efficacy demonstrated in large controlled clinical trials conducted before they received emergency use authorizations from Food and United States Drug Administration.

The study looked at the effectiveness of mRNA vaccines in 3,950 participants in six states over a 13-week period from December 14, 2020 to March 13, 2021. About 74% had at least one injection and tests were performed each. week to catch any infection without symptoms.

“Authorized COVID-19 mRNA vaccines have provided early and substantial protection against infection for our country’s healthcare workers, first responders and other essential front-line workers,” said the CDC director, Rochelle Walensky, in a press release.

New mRNA technology is a synthetic form of a naturally occurring chemical messenger used to instruct cells to make proteins that reflect part of the novel coronavirus. This teaches the immune system to recognize and attack the real virus.

The CDC study comes weeks after real data from Israel suggested the Pfizer / BioNTech vaccine was 94% effective in preventing asymptomatic infections.

Britain and Canada were among the countries that allowed prolonged dose gaps of up to three or four months. UK officials said in January that the data supported his decision to allow for a 12-week gap between doses.

Pfizer and its German partner have warned that they have no evidence to prove it. In their pivotal trials, there was a three-week gap between Pfizer injections and four weeks for the Moderna vaccine.

The CDC said the results of Monday’s study were reassuring that people would start developing protection against the vaccine two weeks after their first dose, although the agency reiterated that the greatest protection was seen among those who did. had received the recommended two doses of vaccine.