February 4, 2021

expert reaction to preprint reanalysing study of real-world Pfizer vaccination outcomes after one dose from Israel

A preprint, an unpublished non-peer reviewed study, estimates the effectiveness of the Pfizer/BioNTech COVID-19 vaccine after one dose by reanalysing a study of ‘real-world’ vaccination outcomes from Israel.

Dr Peter English, Consultant in Communicable Disease Control, Former Editor of Vaccines in Practice Magazine, Immediate past Chair of the BMA Public Health Medicine Committee, said:

“This preprint demonstrates an important aspect of good science: that researchers share their source data with others, so that others can reanalyse the data.  This permits validation/verification (or repudiation) of the original scientists’ conclusions and also – as here – permits further conclusions to be drawn from the data, beyond those drawn (or published by) the original researchers.

“Phase III trials for vaccines have large numbers of participants.  This is necessary to be able to get enough events (cases and adverse events) in vaccine recipients and controls to be able to draw robust conclusions about vaccine efficacy and safety.  Post-implementation studies, by contrast, have very much larger numbers of vaccine recipients – which better enables detection of adverse events, and can provide much more granular (detailed) information about vaccine efficacy.  In this case the authors have looked at the efficacy of the vaccine over time, showing that “vaccine effectiveness was pretty much 0 at day 14 but then rose to about 90% at day 21 before levelling off”.  This is a robust and useful conclusion.

“The authors correctly draw our attention to some limitations to the data (including, for example, its failure to distinguish clearly between mild illness, not requiring hospital admission, and severe illness).

“The preprint (and the source data it relies on) do not provide any direct evidence that the efficacy of a single dose of vaccine will continue up until 12 weeks; but they do support the efficacy of a single dose of vaccine, show that it takes about three weeks for the full benefits to accrue, and the lack of any sign of diminution of efficacy up until 24 days is reassuring.”

Preprint (not a paper): ‘Estimating the effectiveness of the Pfizer COVID-19 BNT162b2 vaccine after a single dose. A reanalysis of a study of ‘real-world’ vaccination outcomes from Israel’ by Paul R Hunter and Julii Suzanne Brainard was posted on medRxiv on Wednesday 3 February 2021.  This work is not peer-reviewed.

https://www.medrxiv.org/content/10.1101/2021.02.01.21250957v1

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www.sciencemediacentre.org/tag/covid-19

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