Question: If you find that (tuberculosis)vaccine how many proves does it have to pass to use it in patients

Rachel Tanner answered on 22 Jun 2020:

Hi Enrique – great question! Any new vaccine candidate has to be tested very rigorously before it can be used in the general population – starting with animal models like mice, and then in humans.

In humans, vaccines get tested in 3 phases:

Phase I study – an initial trial involving a small group of adult participants (up to 100 people). This is carried out to make sure that the vaccine does not have major safety concerns in humans, and also to work out the most effective dose.

Phase II study – a trial in a larger group of participants (several hundred people). Phase II trials check that the vaccine works consistently, and look at whether it generates an immune response. Researchers also start looking for potential side effects.

Phase III study – a trial in a much larger group of people (usually several thousand). Phase III trials gather statistically significant data on the vaccine’s safety and efficacy (how well it works). This means looking at whether the vaccine generates a level of immunity that would prevent disease, and provides evidence that the vaccine can actually reduce the number of cases. It also gives a better chance of identifying rarer side effects not seen in the phase II study.