Trial results have found that having a third or “booster” dose of the Pfizer-BioNTech Covid-19 vaccine is more than 95 per cent effective at preventing disease.
The clinical trial findings, released by the two companies that developed the shot, are described as the first efficacy results from a “randomised, controlled Covid-19 vaccine booster trial”.
There were more than 10,000 participants in the trial, all of whom had completed an initial two-dose programme with the vaccine.
Half the participants then received a third dose of the vaccine, and half were given a placebo, with the third dose given an average of 11 months after the second.
Researchers recorded whether participants subsequently developed symptomatic Covid-19 at least seven days after the booster was given, with individuals followed up for an average of 2.5 months.
In the boosted group there were just five Covid-19 cases, while in the non-boosted group 109 cases were recorded, which gives an efficacy – or effectiveness at preventing disease – of 95.6 per cent.
Prof David Taylor, professor emeritus of pharmaceutical and public health policy at University College London, said the results indicated “having a booster is an extremely sensible idea” for people in at-risk groups.
“The message to everybody, including if you’re 50 or 60 or over, is having a booster dose after six months or longer is extremely sensible,” he said.
In a statement, Ugur Sahin, the chief executive and co-founder of BioNTech, said the results added to the “body of evidence” that the vaccine protected “a broad population of people from this virus and its variants”.
“Based on these findings we believe that, in addition to broad global access to vaccines for everyone, booster vaccinations could play an important role in sustaining pandemic containment and a return to normalcy,” he said.
Pfizer and BioNTech said detailed analysis of the results indicated that efficacy of a booster did not vary with age, sex, race, ethnicity, or any other serious medical conditions a person has.
The companies plan to share the results with regulators, including the Food and Drug Administration in the US and the European Medicines Agency.
A booster programme using the Pfizer-BioNTech vaccine that began in Israel in July has been credited with helping the country overcome its fourth wave of Covid-19 infections.
Infection rates fell faster in over-80s, who were given boosters first, than in other age groups, indicating that the third doses were improving immunity, which may have waned over time after the second dose.
Other countries are also launching booster programmes, including the UK, which began a programme last month focused on over-50s and other vulnerable groups.
In August, Abu Dhabi mandated a third dose of the Sinopharm vaccine for people who had previously received the Chinese-developed shot.
More recently, at the beginning of this month, the UAE authorised booster shots of the Pfizer-BioNTech and Russian-developed Sputnik vaccines for over 60s and members of other vulnerable groups, with the third dose to be given at least six months after the second.
Prof Taylor said it was unclear at the moment whether people would need to have Covid-19 vaccination boosters indefinitely.
“For the next few years, it does look like especially the older population will need top-up immunisation. Whether that will be twice-yearly or yearly we don’t know,” he said.