BERLIN (REUTERS) - Pfizer and German partner BioNTech on Thursday (Oct 21) said data from a Phase III trial demonstrated high efficacy of a booster dose of their Covid-19 vaccine against the virus, including the Delta variant.
They said a trial of 10,000 participants aged 16 or older showed 95.6 per cent effectiveness against the diseases, during a period when the Delta strain was prevalent.
A booster administered about 11 months after the second shot had a favourable safety profile and worked against the highly contagious Delta variant of the coronavirus, they said. The data has not been submitted for peer review.
The trial results come a day after the US Food and Drug Administration authorized booster doses US FDA clears Moderna, J&J Covid-19 boosters, backs use of different vaccine for boost of the Covid-19 vaccines from Moderna and Johnson & Johnson, and said Americans could choose a different shot from their original inoculation as a booster.
Pfizer had said its two-shot vaccine's efficacy drops over time, citing a study that showed 84 per cent effectiveness from a peak of 96 per cent four months after a second dose. Some countries had already gone ahead with plans to give booster doses.
The drugmakers said the median time between the second dose and the booster shot or the placebo in the study was around 11 months, adding that there were only five cases of Covid-19 in the booster group, compared with 109 cases in the group which received the placebo shot.
"These results provide further evidence of the benefits of boosters as we aim to keep people well-protected against this disease," Pfizer CEO Albert Bourla said in a statement.
The median age of the participants was 53 years, with 55.5 per cent of participants between 16 and 55 years, and 23.3 per cent at 65 years or older.
The companies said they would submit detailed results of the trial for peer-reviewed publication, to the US Food and Drug Administration (FDA), the European Medicines Agency, and other regulatory agencies as soon as possible.
The US agencies previously authorized boosters of the Pfizer/BioNTech shot at least six months after the first round of shots to increase protection for people aged 65 and older, those at risk of severe disease and those who are exposed to the virus through their work.
Dr Walid Gellad, a professor at University of Pittsburgh's medical school, said there seems to be a benefit of having the third dose to prevent symptomatic Covid-19, but questioned if the booster was helping younger people as well as older people.
"I'm just still very curious if this is primarily in people who are much, much older. Because what we don't want to do is run out and give boosters to 25-year-olds who had Covid-19 before and got two doses of the vaccine, just based on this press release," Gellad said.
US and EU regulators have already authorised a third dose of Covid-19 vaccines by Pfizer-BioNTech and Moderna for patients with compromised immune systems who are likely to have weaker protection from the two-dose regimens.
