Pfizer reported 90.7% vaccine efficacy in children ages 5-12. What did this really mean?

In mid-October, it was widely published by mainstream media that Pfizer’s mRNA vaccine was 90.7% effective in children.

https://www.theglobeandmail.com/business/international-business/article-pfizer-covid-19-vaccine-shows-907-efficacy-in-clinical-trial-in/

While it sounds impressive, what does it really mean? This is a relative effectiveness rating that compares only those children who become infected as opposed to an absolute effectiveness rating that compares all the children in the trial. So what is the difference?

The reported study included 2,268 children ages 5-12 years. It states that over two thirds in the study were vaccinated, so we can calculate that about 1,518 were vaccinated (experimental group) and 750 were non-vaccinated (control group). It also states that 16 children in the non-vaccinated group tested positive for SARS -CoV-2, while only 3 in the vaccinated group tested positive. If the groups were even in numbers, there may have been twice as many (32) infected in the non-vaccinated group.

The relative effectiveness rating is calculated by subtracting the number infected in the experimental group (3) from the number infected in the control group (32) which is 29. (32 – 3=29). This number is then divided by the total number infected (32) in the control group and expressed as a percent. (29/32 X 100 = 90.7%) This certainly sounds impressive, doesn’t it?

BUT, what is the absolute effectiveness rating when we consider all the children in the group. We know that 32 out of 1500 became infected in the control group, which is about 2.1%. There were 3 out of 1518 in the experimental group who became infected, which is about 0.2%. The absolute effectiveness rating subtracts the percentage infected in the experimental group from the percentage infected in the control group. (2.1% – 0.2% = 1.9%)

This means that only 1.9% of children would be assisted in gaining some immunity by the experimental vaccine with its inherent risks to children now and in the future. This number doesn’t sound nearly as impressive, especially considering the minimal risk to children who get a natural infection!

For more information on effectiveness ratings, the CCCA can help you.