The randomized, controlled trial evaluated the efficacy and safety of a 30-µg booster dose of the Pfizer-BioNTech COVID-19 Vaccine in more than 10,000 individuals 16 years of age and older.
In people who had previously been vaccinated with the two-dose Pfizer/BioNTech regimen, a booster shot restored vaccine protection against COVID-19 to the high levels achieved after the second dose: showing a relative vaccine efficacy of 95.6% when compared to those who did not receive a booster.
The trial was conducted during a period when Delta was the prevalent strain.
These data will now be submitted to regulatory agencies to further support licensure of a booster dose.
'Boosters have a critical role to play in addressing the ongoing public health threat'
All trial participants had previously completed the primary two-dose series of the Pfizer-BioNTech vaccine, and then were randomized 1:1 to receive either a 30-µg booster dose (the same dosage strength as those in the primary series) or placebo.
The booster shot (or placebo) was administered around 11 months after the second dose of the initial regimen. Symptomatic COVID-19 occurrence was measured after administration of the booster dose, with a median follow up of 2.5 months.
In the trial, there were 5 cases of COVID-19 in the booster group, and 109 cases in the non-boosted group. The observed relative vaccine efficacy of 95.6% (95% CI: 89.3, 98.6) reflects the reduction in disease occurrence in the boosted group versus the non-boosted group in those without evidence of prior SARS-CoV-2 infection.
Efficacy was consistent irrespective of age, sex, race, ethnicity, or comorbid conditions.
Albert Bourla, chairman and CEO, Pfizer, said: “In addition to our efforts to increase global access and uptake among the unvaccinated, we believe boosters have a critical role to play in addressing the ongoing public health threat of this pandemic.
“We look forward to sharing these data with health authorities and working together to determine how they can be used to support the rollout of booster doses around the world.”
Last month, the FDA authorized booster doses of the vaccine for higher risk people (individuals 65 years of age and older, individuals 18 through 64 years of age at high risk of severe COVID-19, and individuals 18 through 64 years of age with frequent institutional or occupational exposure to SARS-CoV-2). A booster dose is also authorized in the EU, with each Member State deciding its own policy on how these will be administered.