In a UK-based research, it was found that after the first dose of AstraZeneca or Pfizer vaccine, the Covid19 infections in adults of all ages fell by 65% which scientists said showed the real-world impact of the nation’s immunization campaign against the pandemic.

Crucially, the research was conducted at a time when a new and more infectious variant of the coronavirus, called B1.1.7, was dominant in Britain. Still it found that vaccination was just as effective in elderly people and those with underlying health conditions as it was in the young and healthy.

As the data were published, health minister James Bethell said in a statement, “These real-world findings are extremely promising.” He also added that the data showed that Britain’s Covid-19 vaccination programme, one of the world’s fastest drives, was having a “significant impact”.

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The data came from two studies that are part of the Covid-19 Infection Survey. This survey was a collaboration between Oxford University, the government’s health department, and the Office of National Statistics. On Friday, both studies were published online as preprints and have not yet been peer-reviewed.

The researchers analyzed more than 1.6 million test results from nose and throat swabs taken from 373,402 study participants between December 1, 2020 and April 3, 2021.

They found that 21 days after a single dose of either the AstraZeneca or Pfizer-BioNTech vaccine with no second dose, the rates of all new Covid-19 infections had dropped by 65%.

This fall in infection-rates included a drop in symptomatic infections by 74% and a drop in infections with no reported symptoms by 57%.

The study found that the reductions in overall infections and in symptomatic infections, were even greater after a second dose 70% and 90% respectively, and were similar to effects in people who had previously had a Covid-19 infection.

The second study looked at the levels of antibodies to the SARS-CoV-2 virus to see how they changed after one dose of either vaccine, and after two Pfizer doses.

Results showed that antibody responses to a single dose of either vaccine were slightly lower in older people, but higher across all ages after two Pfizer doses.

Official data showed on Wednesday that more than 33 million people in Britain have received the first dose of a Covid-19 vaccine, with more than 10 million having had two doses.