Pfizer/BioNTech and Moderna have each tested their on at least 30,000 volunteers (Pfizer/BioNTech: around 44,000, Moderna: around 30,000). Half of those enrolled in each of the studies received the vaccine and half received a placebo. The studies were double blind, meaning that neither the test subjects nor the investigators knew who had received the vaccine and who had received a placebo. After a certain number of subjects had reported infection, the study investigators ran a check to determine how many of those infected had received the vaccine and how many had received a placebo. In the case of the Pfizer/BioNTech vaccine, 90 of the 95 infected individuals were in the placebo group. In the case of the Moderna vaccine, 162 of the 170 infected individuals were in the placebo group. This means that only 5 individuals from the Pfizer/BioNTech study and only 8 individuals from the Moderna study were infected despite having received the vaccine. This shows that both vaccinations show an efficacy rate of over 90 percent.