An Early Look at the Covid-19 Vaccine – Behind the Numbers

Dr. Swanz has a new YouTube video where he discusses the early findings in the Pfizer Covid-19 vaccine efficacy study – Covid-19 Vaccine and the Early Findings

So let’s talk about the very exciting news regarding the development of the Covid vaccine.

First the FDA has set the required efficacy for the Covid-19 vaccine to come to market at 50%. 

“To ensure that a widely deployed COVID-19 vaccine is effective, the primary efficacy endpoint point estimate for a placebo-controlled efficacy trial should be at least 50%, and the statistical success criterion should be that the lower bound of the appropriately alpha-adjusted confidence interval around the primary efficacy endpoint point estimate is >30%” ( Industry Guide for Development and Licensure of Covid Vaccine – June 2020

What’s important to note here is that the FDA under the Emergency Use Authorization is allowing for clinical endpoints to be the deciding factors related to the efficacy trials, not the immune endpoints. An immune endpoint would be an actual marker of immunity being examined in the individual receiving the vaccine, such as – did the individual’s body produce an antibody response to the vaccine? A clinical endpoint doesn’t need to consider the individuals that are being given the vaccine and instead considers the entire vaccine group in comparison to the entire placebo group.


It was recently publicized that the Pfizer vaccine may be more than 90% effective. That sounds awesome!  ( This is a clinical endpoint result and here’s some clarification about what that means.


The Pfizer study was looking at cases of covid-19 a week after administration of the second dose of the vaccine or placebo and gave these results:

  • 20,000 individuals given placebo and 86 cases of Covid-19
  • 20,000 individuals given vaccine and only 8 cases of Covid-19
  • So of 94 total cases of Covid-19 only 8 happened in the vaccine group. That’s the 91.5% improvement in the vaccine group as compared to the placebo group that has been widely publicized.
  • 86 cases out of 20,000 is an infection rate in the placebo group of 0.43%. Which is right in alignment with what has been observed with Covid-19 in the general population. 
  • 8 cases out of 20,000 in the vaccine group is an infection rate of 0.04%. That’s an improvement, but what does that mean in real numbers? One alternative way to explore these results is by looking at the NNTV.
  • The Number Needed To Vaccinate (NNTV) is the number of vaccines that have to be given to prevent 1 case of Covid-19. Based on these early findings the NNTV can be calculated to be 256. The difference between the vaccine and placebo group is 78 cases of Covid-19 and 20,000 vaccines had to be administered to eliminate those 78 cases from the vaccine group. Meaning 256 people in the vaccine group were vaccinated in order to stop 1 case of Covid in that group. 255 people did not benefit from the vaccine based on the clinical endpoint measure (these individuals statistically would not have developed covid-19 anyway), yet may be subjected to any of the benefits or adverse effects of the vaccine described and not yet described.
  • Because we are looking at the end point of covid infections without looking at individual immune reactions we do not yet have any indication of other benefits the 255 may have received from getting the vaccine. 

What sort of adverse effects are people experiencing with the mRNA vaccines in the studies?

Injection site pain, fatigue, myalgia, arthralgia, headache, and erythema/redness at the injection site were the most common solicited adverse events in a prior analysis. The company noted that these solicited adverse reactions increased in frequency and severity after the second vaccine dose.” ( 

The development of the Covid-19 vaccine is an unprecedented situation in the development of vaccines in the US.

First it is an entirely new type of biologic agent – an mRNA vaccine. This has never been done before. 

Second, because both of the companies that are furthest along are asking for an Emergency Use Authorization (EUA) from the FDA to allow these vaccines to come to market without requiring the normal hoops that all other vaccines have had to jump through.

“the FDA’s Vaccines and Related Biological Products Advisory Committee, which is expected to meet on Dec. 10, will review the trial data before the agency grants an EUA to Pfizer or Moderna. Then the FDA will post the data publicly.” (

This is happening! It’s important that we stay informed and aware of how this may impact us all, both in our current health situation with the Covid-19 infection and also for the development of future biologic agents. 

Thanks for reading my blog and watching my videos. You can reach out to me on the Dr. Swanz website connect page. 

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