The Pfizer Covid Vaccine Trials – Behind the Numbers

The Pfizer-BioNTech COVID-19 Vaccine has been approved for Emergency Use Authorization in the United States based on the early findings of the phase 2 and phase 3 clinical trial that included around 40,000 people split roughly in half into both a placebo and a vaccine test group. The fact that we are now distributing this vaccine to the general public while the full trials are not yet complete is unprecedented in the history of vaccine development. My hope is that this new vaccine and new vaccine technology will be safe and effective as well as one of the important steps we can take as a society to get back to normal.

You can watch a YouTube video of me discussing this information here – Dr. Swanz Behind the Numbers of the Pfizer Covid Vaccine Trial

Here’s some of the numbers that I feel are important from the trial that have not yet been circulated or discussed extensively in the general public. I think it is important that as individuals decide about utilizing this new and not fully tested vaccine they can consider all of the data we have so far about the testing and the impact the vaccine had during the testing.

The 40,000 people that participated in the clinical trial are demographically broken down like this:

  • 50.6% male and 49.4% female
  • 83.1% White
  • 9.1% Black
  • 28% Hispanic / Latino
  • 4.3% Asian
  • 0.5% American Indian / Native
  • 21.4% were at least 65 years of age or older
  • 4.3% were at least 75 years of age or older

There was a list of adverse effects reported during the study and something interesting worth mentioning is that the adverse effects were significantly more pronounced and frequent after the administration of the second dose of the vaccine or placebo. In addition adverse effects were reported at a higher incidence rate in the participants 55 years of age or younger. Here’s a breakdown of the adverse effects. I’m including the percentage of incidence in the population over 55 in parenthesis:

  • Fever over 100 degrees – 15.8% (10.9%) vaccine group / 0.5% (0.2%) placebo group
  • Fatigue – 59.4% (50.5%) vaccine group / 22.8% (16.8%) placebo group
  • Headaches – 51.7% (39%) vaccine group / 24.1% (13.9%) placebo group
  • Chills – 35.1% (22.7%) vaccine group / 3.8% (2.8%) placebo group
  • New or worse muscle pain – 37.3% (28.7%) vaccine group / 8.2% (5.3%) placebo group
  • New or worse joint pain – 21.9% (18.9%) vaccine group / 5.2% (3.7%) placebo group
  • Required NSAIDs afterwards – 45% (37.7%) vaccine group / 12.6% (9.8%) placebo group

The study looked at confirmed cases of Covid-19 one week after administration of the 2nd dose of the vaccine or placebo. A confirmed case required at least one symptom of Covid and a positive PCR diagnostic test. The published findings are that there were 9 cases of Covid found in the vaccine group and 169 cases of Covid in the placebo group. This results in the 94.6% efficacy that was utilized for the evaluation by the FDA that granted the Emergency Use  Authorization of the vaccine. 

Something that has not been publicized in a similar manner are the cases of suspected but unconfirmed cases of Covid-19 in the study. These cases appeared to be examples of Covid infection but did not meet the requirements of the confirmed cases. There were 3410 suspected but unconfirmed cases of Covid during the study. There were 1594 suspected but unconfirmed cases in the vaccine group. There were 1816 suspected but unconfirmed cases in the placebo group. We can remove the suspected cases that happened within a week of the injection, so that takes 409 from the vaccine group and 287 from the placebo group. When the suspected but unconfirmed cases of Covid are included in the efficacy analysis the efficacy of the Covid-19 vaccine drops from 94.6% to around 29%. I think we can confidently say that the Covid-19 vaccine is effective somewhere between 29% to 95% at preventing a Covid-19 infection.

Things we do not yet know about the covid vaccine:

  • Does it decrease transmission of Covid-19
  • How long does protection from developing a Covid-19 infection last
  • Is the vaccine necessary or valuable after someone has recovered from a Covid-19 infection
  • Could the vaccine result in a situation where the virus can be spread asymptomatically in a manner similar to what happens with individuals administered the pertussis vaccine?

As more individuals choose to get the vaccine, hopefully many of these questions will be addressed. Thanks so much for checking this out. 

FDA Briefing Document from Pfizer

Peter Doshi: Pfizer and Moderna’s “95% effective” vaccines—we need more details and the raw data

Asymptomatic transmission and the resurgence of Bordetella pertussis

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