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).
If many or most of these suspected
cases were in people who had a false negative PCR test result, this
would dramatically decrease vaccine efficacy. But considering that
influenza-like illnesses have always had myriad causes—rhinoviruses,
influenza viruses, other coronaviruses, adenoviruses, respiratory
syncytial virus, etc.—some or many of the suspected covid-19 cases may
be due to a different causative agent.
But why should etiology matter ? If
those experiencing “suspected covid-19” had essentially the same
clinical course as confirmed covid-19, then “suspected plus confirmed
covid-19” may be a more clinically meaningful endpoint than just
confirmed covid-19.
However, if confirmed covid-19 is on
average more severe than suspected covid-19, we must still keep in mind
that at the end of the day, it is not average clinical severity that
matters, it’s the incidence of severe disease that affects hospital
admissions. With 20 times more suspected covid-19 than confirmed
covid-19, and trials not designed to assess
whether the vaccines can interrupt viral transmission, an analysis of
severe disease irrespective of etiologic agent—namely, rates of
hospitalizations, ICU cases, and deaths amongst trial participants—seems
warranted, and is the only way to assess the vaccines’ real ability to
take the edge off the pandemic.
There is a clear need for data to
answer these questions, but Pfizer’s 92-page report didn’t mention the
3410 “suspected covid-19” cases. Nor did its publication in the New England Journal of Medicine.
Nor did any of the reports on Moderna’s vaccine. The only source that
appears to have reported it is FDA’s review of Pfizer’s vaccine.