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Early batches of Pfizer’s Covid vaccine were ‘unstable’

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Early batches of Pfizer’s mRNA Covid vaccine were unstable, leaked documents from the European Medicines Agency (EMA) have revealed.

The instability makes the vaccine ineffective against the SAR-CoV-2 virus—responsible for Covid-19—and could even make it unsafe to use.

The EMA discovered the instability when it was inspecting early batches last November as part of the approval process that would allow the roll-out of a Europe-wide mass vaccination programme. RNA integrity had dropped to just 55 percent, far below the 75 percent the EMA had been told was needed to make the vaccine effective.

Despite its concerns, the EMA gave its approval just a month later to the manufacturers, Pfizer-BioNTech, making it the first ever Messenger RNA (mRNA) vaccine to be licensed.

A mRNA vaccine works by ‘teaching’ cells to make a protein that triggers an immune response—but it’s vital it is stable and contains a complete mRNA molecule. “Even a minor degradation, anywhere along a mRNA strand” renders the vaccine ineffective, says Daan Crommelin, a biopharmacist.

The EMA’s concerns about the early batches of the vaccine were uncovered when its database was hacked and 40 Mb of classified data was posted on the ‘dark web’. The agency was worried about Pfizer’s manufacturing processes that had produced very low quantities of intact mRNA, yet its public pronouncements on its website just a month later extolled the “consistent and acceptable” levels of the new vaccine’s quality.

The Pfizer vaccine is the first of a new wave of mRNA vaccines and therapeutics. Moderna and CureVac are also developing their own products—and yet none was prepared to reveal the percentage integrity of mRNA that makes them effective when questioned by journalists at the BMJ (British Medical Journal).

The acceptable level is commercially confidential, the UK’s Medicines and Healthcare products Regulatory Agency (MHRA) said.

(Source: BMJ, 2021; 372: n627)

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Article Topics: vaccination, vaccine
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