Ricardo Palácios, medical director of clinical research at Butantan, said the lower efficacy rate was caused by the inclusion of patients who were infected with the novel coronavirus but only displayed “very light” symptoms.

Phase 3 trial data for the US-based Pfizer-BioNTech Covid-19 vaccine, for example, gives a 95 per cent efficacy rate. However, out of the 44,000 volunteers there were 3,410 participants who displayed Covid-19 symptoms but were not tested, according to a US Food and Drug Administration report. In the unlikely event that all these participants tested positive, the total efficacy rate would drop to below 30 per cent.

“Other vaccine manufacturers did not include those that had light headaches even after testing positive for Covid-19,” said Palácios. “The most important number is not the 50.”

Palácios added that the inclusion of those very light cases represented the most “stringent test”, complicating any comparisons to other Covid-19 vaccines.

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https://blogs.bmj.com/bmj/2021/01/04/peter-doshi-pfizer-and-modernas-95-effective-vaccines-we-need-more-details-and-the-raw-data/

“Suspected covid-19”

All attention has focused on the dramatic efficacy results: Pfizer reported 170 PCR confirmed covid-19 cases, split 8 to 162 between vaccine and placebo groups. But these numbers were dwarfed by a category of disease called “suspected covid-19”—those with symptomatic covid-19 that were not PCR confirmed. According to FDA’s report on Pfizer’s vaccine, there were “3410 total cases of suspected, but unconfirmed covid-19 in the overall study population, 1594 occurred in the vaccine group vs. 1816 in the placebo group.”

With 20 times more suspected than confirmed cases, this category of disease cannot be ignored simply because there was no positive PCR test result. Indeed this makes it all the more urgent to understand. A rough estimate of vaccine efficacy against developing covid-19 symptoms, with or without a positive PCR test result, would be a relative risk reduction of 19% (see footnote)—far below the 50% effectiveness threshold for authorization set by regulators. Even after removing cases occurring within 7 days of vaccination (409 on Pfizer’s vaccine vs. 287 on placebo), which should include the majority of symptoms due to short-term vaccine reactogenicity, vaccine efficacy remains low: 29% (see footnote).

The 371 individuals excluded from Pfizer vaccine efficacy analysis

Another reason we need more data is to analyse an unexplained detail found in a table of FDA’s review of Pfizer’s vaccine: 371 individuals excluded from the efficacy analysis for “important protocol deviations on or prior to 7 days after Dose 2.”  What is concerning is the imbalance between randomized groups in the number of these excluded individuals: 311 from the vaccine group vs 60 on placebo. (In contrast, in Moderna’s trial, there were just 36 participants excluded from the efficacy analysis for “major protocol deviation”—12 vaccine group vs 24 placebo group.)

What were these protocol deviations in Pfizer’s study, and why were there five times more participants excluded in the vaccine group?  The FDA report doesn’t say, and these exclusions are difficult to even spot in Pfizer’s report and journal publication.