Ahead of FDA adcomm, Pfizer, Moderna say COVID jab efficacy dips

Pfizer and Moderna have both reported data that they say backs up the need for booster shots of their COVID-19 vaccines ahead of an FDA advisory committee meeting tomorrow, although the regulator seems less convinced.

Documents published ahead of the panel by the FDA reviewers suggest that there is some evidence from observational studies that protection may be starting to fall away, but overall the available data suggests that “currently US-licensed or authorised COVID-19 vaccines still afford protection against severe…disease and death”.

The Biden administration has said it plans to start offering COVID-19 booster doses next week, pending the outcome of the adcomm meeting.

Pfizer meanwhile said in its submission that a third dose of its BioNTech-partnered Comirnaty shot – the subject of the meeting – is warranted as “the totality of the available data supports the public health need” for a booster approximately six months after the second dose.

It highlights data from the US and Israel which suggests that as the highly transmissible delta variant began to become dominant protection against COVID-19 infection wanes approximately 6 to 8 months after the primary course of injections.

Looking at breakthrough infections, there was a higher incidence among people vaccinated in the early stages of Comirnaty’s testing  – at least eight months before 1 July 2021 – compared to individuals vaccinated after that time point.

That is backed up by data from Israel showing a greater then two-fold increased risk of breakthrough infection for people vaccinated in January of this year, compared with those vaccinated in April.

The reduction in protection likely stems from waning effectiveness overall, rather than delta escaping vaccine protection, given that its studies suggested an initial 90% efficacy against the variant, according to Pfizer. Administering a third dose restores protective efficacy back up to 95% or more, it said.

Meanwhile, Moderna also reported new data with its mRNA-1273 jab – which won’t be discussed at the FDA meeting – that also indicates waning protection. It said an analysis of its phase 3 COVE study found a higher risk of breakthrough infection in people vaccinated last year compared to those who received the shot in 2021.

The company also reported new data on mRNA-1273’s effectiveness against delta that found it was 87% effective at preventing a COVID-19 diagnosis, and 96% effective at preventing hospitalisation.

The adcomm meeting is taking place after two departing FDA officials – Dr Marion Gruber and Dr Philip Krause – signed their names to a letter published in The Lancet arguing that the current vaccines’ efficacy against severe disease remains high, and that side effects linked to them – while rare – mean that a widespread booster campaign should be approached with caution.

WHO moratorium call extended

The World Health Organization (WHO) meanwhile has extended its call for a moratorium on COVID-19 booster doses until the end of the year, arguing that there is more to be gained from diverting available stocks to countries that have much less vaccine coverage.

Around 5.5 billion vaccine doses have been administered globally, but 80% have been given out in high- or upper-middle income countries, it said.

The WHO had previously sought a moratorium until the end of this month. Several countries – including the UK and US – have indicated they intend to ignore that request.

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