Pfizer/BioNTech’s New Vaccine Is Safe and Effective
Tags: Biotechnology, Covid 19, Science, Health, Coronavirus

4. The study…

Pfizer/BioNTech’s Phase I trial showed the preliminary safety of delivering two 30-microgram doses of BNT162b2 to healthy adult men and women in Germany and the U.S. Passing that first trial let the companies progress to this current more rigorous trial.

The phases of a drug clinical trial are explained on the FDA’s website here. The bite-sized summary of clinical trials is:

Phase I — about a hundred healthy or sick volunteers who are studied for a few months to determine the safety and the appropriate dose of the drug

Phase II — a couple hundred sick volunteers who are studied for months to a couple years to determine the effectiveness and side effects of the drug

Phase III — thousands of sick volunteers who are studied for up to four years to determine the effectiveness and to learn about adverse reactions to the drug

The Phase II/III trials further tested the BNT162b2 vaccine’s safety (with many more people, and over longer time periods), and most importantly the vaccine’s efficacy. The latest trial used the same two 30-microgram doses, injected into the shoulder muscle, three-weeks apart. The BNT162b2 vaccine was compared to a placebo (just a saline solution with no active drugs).

A total of 43,448 people took part in the clinical trial and were injected with either the vaccine or the placebo. A web-based app randomly assigned each patient to receive either the drug or the placebo. Neither the patients nor the staff who administered the injections knew who got what injection — we say they were blind to the study. This overall study design is called a randomized, double-blind, placebo-controlled clinical study — the gold standard.

A placebo shows that the vaccine is indeed better than doing nothing. A good scientific clinical study always compares the drug to a placebo, called a control.

Blinding the study means there is no way for either the volunteers or the study staff to intentionally or unintentionally bias the study (such as putting healthier people in the vaccine group and putting sicker people in the placebo group, falsely making the vaccine look better than it is).

Randomizing is essential to make sure our two groups, the vaccine group and the placebo group, are as similar as possible. That we are comparing “apples to apples”.

And finally, a large sample size ensures that the results of the clinical study are real and not just from pure chance, from getting lucky and flipping heads five times in a row.

Table 1 from paper summarizing the study demographics (image from Polack et al, 2020)

Patients electronically recorded any local or systemic “adverse events”, or if the patient needed to use medication to treat fever or pain within 7 days of each dose. This was the main safety data.

The natural yardstick for measuring the vaccine’s effectiveness is to simply count the number of COVID-19 cases in the study. Then compare the people given the vaccine to those given the placebo and determine which group had more cases of the disease.

People who ended up showing a standardized set of COVID-19 symptoms, or who were tested and confirmed by RT-PCR, were counted as cases. Another important metric was how severe the case was, especially since it is severe COVID-19 which is overwhelming the medical system thus exacerbating the fatalities associated with the disease.