Clinical trial of vaccines and drugs

Vaccines and drugs are subjected to clinical trials to establish their safety and effectiveness before being licensed for use.

Subjects in clinical trials are divided into groups in a randomised way to reduce bias in the distribution of characteristics such as age and gender. Answer: All individuals have an equal chance of being in either group.

In a double-blind trial neither the subjects nor the researchers know which group subjects are in to prevent biased interpretation of the results.

One group of subjects receives the vaccine or drug while the second group receives a placebo-control to ensure valid comparisons.

At the end of the trial, results from the two groups, which must be of a suitable size to reduce the magnitude of experimental error, are compared to determine whether there are any statistically significant differences between the groups.