Question: How long (on average) does it take to develop a vaccine?

Jenny Hill answered on 10 Jan 2022:

Well there are some diseases that scientists have been working on for decades and they haven’t managed to make a vaccine that works yet, like HIV, the first vaccine trial for HIV started in 1987 and there are still trials today. If we only count the cases where a vaccine has been successfully developed then 10 – 15 years is probably about right. This website (https://wellcome.org/news/quick-safe-covid-vaccine-development) has a good explanation of the stages and how long they take as well as how it was possible to develop COVID-19 vaccines more quickly.

The longest parts are ususally the first stage – working out what part of the bacteria or virus to target and how to make the components of the vaccine, and the last stage – the clinical trial that tests whether the vaccine can protect people. Typically in this last stage the number of infections in a group of people who received the trial vaccine will be compared with the number in a group who didn’t get the vaccine. It can take a long time for enough people to get infected across the whole study to see a difference between the two groups. With COVID-19 because there have been periods with very high rates of infection this has helped to make this stage pass quickly.