variable lnp potency

First posted online: 4 May 2022

Do Pfizer’s shots vary in potency and safety? Pfizer’s new clinical trial documentation lends support to the idea there is wide variability in the administered product due to these possible factors:

  • dilution errors

  • excess temperature degrading LNPs

  • other human error

So unsuitable were 105 of the administered doses, volunteers receiving these shots could not contribute efficacy data. Almac, who partnered with Pfizer, excluded these subjects due to:

"IP [investigational product] administered that was deemed not suitable for use by Almac"

Importantly, these problem doses were spread out both temporally and spatially, administered on a daily basis (August/September 2020) across different test sites. Mostly the same pattern. Dud doses injected one day, seemingly retrospectively deemed “not suitable”.

These problem doses are separate from a smaller number of exclusions (67) due to explicit dosing errors, logged as:

"Dosing/administration error, subject did not receive correct dose of vaccine"


  • If not dosing errors, what were the causes?

  • In the real-world rollout, why do we never hear about this phenomenon?

  • Since commercial batches were initially poorer than clinical supply batches (EMA), is this even more of a problem in the real world?

105 doses were deemed unsuitable by staff at Almac

67 separate dosing errors are recorded as protocol deviations