Results from first ‘gold standard’ COVID booster vaccine trial

Jolyon Attwooll

25/10/2021 4:50:11 PM

With an announcement pending on Pfizer vaccine boosters in Australia, a new trial suggests they increase vaccine efficacy to 95.6%.

Health worker preparing Pfizer vaccine.
An official announcement is set to be made shortly on a booster program, which is likely to use the Pfizer vaccine in its initial stages.

Pfizer and BioNtech have announced promising results for the first larger, randomised controlled trial designed to assess the efficacy of their COVID-19 vaccine as a booster.
In a press release on Friday, the pharmaceutical and biotech companies who collaborated in the vaccine’s development reported a third dose raised efficacy by 95.6% compared to a group that had only received the two-dose primary course.
They describe the data as being the first to show efficacy results from a randomised, controlled COVID-19 vaccine booster trial.
The analysis, conducted after Delta had become the dominant strain, involved more than 10,000 people aged 16 and older, with a median age of 53, who had all completed the primary course of vaccination using the Pfizer vaccine with no prior evidence of infection with SARS-CoV-2.
Participants were randomised to receive either a booster with the same strength as doses in the initial vaccination, or a placebo, and the results showed that a booster dose restored ‘vaccine protection against COVID-19 to the high levels achieved after the second dose’.
The booster injection was given a median 11 months after the second dose, the companies’ announcement states, with testing for symptomatic COVID-19 taking place at least seven days after the booster or placebo was administered. The median follow-up time was two and a half months following the booster.
The companies’ announcement declared the results surrounding the booster’s efficacy as ‘consistent irrespective of age, sex, race, ethnicity, or comorbid conditions’.
They also declared the adverse event profile as ‘consistent with other clinical safety data’ for the vaccine, and that no safety concerns were identified.
There were no further details on where the randomised controlled trial took place, but the data is most likely to have come from Israel where the world’s first booster program was put in place.
Results have not yet been peer-reviewed, but the companies said the data would be submitted for independent scrutiny and shared with regulatory authorities around the world.
Previous studies have suggested boosters are highly effective, but without the ‘gold standard’ scientific rigour of a randomised controlled trial.
Among the earlier research is a pre-print article released this month using Israeli medical data for 4,621,836 individuals. It suggested COVID-19 infection rates were around 10-fold lower in those that had a booster, and that there were also significant declines in the rate of severe illness in the 40–60 and over-60 age groups.
Pfizer has already obtained regulatory approval for the administration of boosters in several locations throughout the world, including in the United States and the European Union.
Last week, Federal Health Minister Greg Hunt said he believes a booster program could begin in November if the right approvals come through.
The Australian Technical Advisory Group on Immunisation (ATAGI) has already recommended a third dose for the severely immunocompromised, although this is counted as part of the primary vaccination process rather than as a booster.
Details on the timings and logistics of a booster program rollout in Australia are due to be announced this week, provided the use of COVID-19 boosters is granted by the Therapeutic Goods Administration (TGA).  
Deputy Chief Medical Officer Professor Michael Kidd said on Sunday that a booster program could begin as early as 8 November and would likely target the aged care and disability sectors, as well as healthcare workers in its initial phases.
This week, Nine Newspapers also reported that those who had a course of AstraZeneca with a shortened gap between doses could be encouraged to wait no longer than six months after their second dose to get a booster.
The recommended time between AstraZeneca vaccine doses was shortened to 4–8 weeks by ATAGI in July for those in outbreak areas, a move designed to accelerate the vaccine rollout. It remained at 12 weeks in other areas, which is the interval research suggests maximises the vaccine’s efficacy.
RACGP NSW&ACT Chair Dr Charlotte Hespe said the shortened interval is relevant to both younger people who had their vaccination at a later stage and older people who had put off their initial vaccination until the Delta outbreak took hold.
‘The point is they do it at six months from the second dose and don’t delay,’ she told newsGP.
However, Professor Kidd also sought to reassure this cohort, saying that they would remain protected as long as the dosage interval was within the advised timeframe.
‘There is no evidence that we have available that if you received your [AstraZeneca] vaccine in a shorter period, as long as it’s within that 4–12 weeks, that you’re at greater risk of losing your immunity,’ he said.
Pfizer is the only pharmaceutical company so far to have submitted data to the TGA for approval for a booster program.
Officials from the TGA and ATAGI were due to meet on Monday to look at data from Pfizer on COVID-19 booster doses, the ABC reported.
Booster shots are likely to be available six months after a second dose, Lieutenant General John Frewen, the head of the Federal vaccination taskforce, also told media this week. He also said a decision from ATAGI is ‘imminent’.
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