More than 99.9% of the Pfizer Vaccine Placebo Group did not get a severe case of covid

covid vaccine Nov 28, 2020

The Pfizer vaccine trial has 43,000 participants. Exact breakdown between treatment and placebo groups is not given, but they do provide the number of covid cases in each group. Currently, there are 162 covid cases in the placebo group.

Assuming a 50/50 split, 99.25% of the placebo group did not get covid.

Additionally, only 9 in the placebo group had a "severe case" and no one died. That is 99.96% in the placebo group did not have a severe case.

Caveats

We need to know the overall infection rate of the state/country where the participants lived during the time frame of the trial (July 27 - Nov 13) to make a fair comparison. Example: If the participants that lived in New York City during the dates of the trial tested 0.5% positive and NYC as a whole tested 0.1% positive, then being in the placebo group was at higher risk than the general population. I just made up those numbers, but it's not possible to compare the placebo group to the general population without the location (among other attributes) of each participant.

Estimation

Even so, we can make an estimation as to how the placebo group compares to the overall population using the US as an example. In the US, 7.4 million confirmed cases were recorded during the time frame of the trial equaling about 2.2% of the population. This number is approximately 3x higher than that of the placebo group (.75%). We know the real number of infections to be at least 3 or 4 times this amount. I'm not exactly sure how the participants in the trial were managed, but if all of them were tested, or at the least, kept a closer eye on, then the placebo group could have covid incident rate much lower than the general population.

Applicability

The participants in the trial come from a self-selected group healthier and younger than the population at large. Only 8 participants in the treatment group tested positive for covid, but I'm not sure how well these results will apply to those who are most at risk (Obese and diabetic people over the age of 70).

Conclusions

We have a vaccine trial where 99.25% of the placebo group did not have covid, 99.96% did not have a severe case, and 100% survived. The only thing this trial shows is how weak covid is on self-selected volunteers that are healthier and younger than the population most at risk.

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