Pfizer and BioNTech’s Covid-19 vaccine begins working around 10 days after the first dose, according to new documents released by the U.S. regulator ahead of a consultative meeting this week to discuss whether to grant it emergency approval.
The report raised hopes that the vaccine could begin to ease pressure on overwhelmed hospitals soon after its deployment. It’s already UK approved but will be the first to be considered for emergency use authorization in the United States.
The Food and Drug Administration confirmed the vaccine shows a high efficacy rate of 95% on average, with 93.8% in participants over 55 years of age. The vaccine requires two injections, spaced 21 days apart. It is not yet clear how long the protection of the vaccine lasts.
The documents provide the most detailed data to date on participants, including showing that it worked well regardless of race, age or weight.
Scientists at the regulator have not raised significant safety concerns – although Tuesday’s report said there was not enough evidence yet on its safety in children, pregnant and lactating women, as well as people with an HIV immune system. The most common side effects are pain at the injection site, fatigue, and headaches.
There were more cases of Bell’s palsy, facial muscle weakness, and appendicitis in the vaccine group than in the placebo group. But the FDA said the incidence was no higher than in the general population of the same age.
There were four deaths in the placebo group and two in the vaccine group, at a rate similar to that in the general population. With a trial of about 44,000 people, it’s usual to see death and serious illness.
The FDA’s vaccine advisory group will meet publicly on Thursday to discuss whether the Pfizer / BioNTech vaccine should receive emergency use authorization.
The regulator is asking advisers to consider whether it is reasonable to believe that the vaccine prevents Covid-19 in people aged 16 and over, and whether the benefits outweigh the risks. The FDA is not bound by the decisions of its advisers.
Scientists said the vaccine will continue to be studied after emergency approval, as it is being rolled out to a larger population.
In addition to monitoring side effects that may only appear in a larger group, the FDA has suggested that there should be additional evaluations to see if the vaccine could prevent asymptomatic Covid-19 infection. A significant number of people can spread the virus without experiencing symptoms.
The FDA warned that if participants had a vaccination immediately after emergency approval, it could interfere with the ability to collect follow-up data. He said strategies should be considered to balance the need for this data with ethical obligations to placebo beneficiaries.
The documents indicate that Pfizer would like to cancel the blind, giving placebo participants the opportunity to be vaccinated. For the first six months after the second dose, this will only be for people who request the vaccine.