How are vaccines tested?
All vaccines undergo rigorous safety testing during their development and use. There are three phases of clinical trials and the data from these trials is reviewed by regulators in each country before being approved. The vaccines are then rigorously monitored for safety.
New vaccines undergo three phases of clinical testing in progressively larger groups of human participants. These are designed to look for any potential side-effects and safety concerns, to work out the best doses required and examine how well the vaccine works. By the end of these clinical trials, the vaccine will have been tested in more than 3,000 people.
The data from each stage of this testing is then passed to regulating authorities, such as the Medicines and Healthcare products Regulatory Agency (MHRA) in the UK, the European Medicines Agency (EMA) or the US Food and Drug Administration (FDA). Scientists and medical doctors examine the data from the trials, alongside manufacturing and quality control data, to decide whether a vaccine can then be approved – or licensed – for use.
Once a new vaccine is approved for use, there is a robust, ongoing monitoring process where suspected side-effects are reported regularly to regulators by the manufacturers, health professionals and patients themselves. In the UK this is done via the Yellow Card Scheme run by the Medicines and Healthcare products Regulatory Agency (MHRA). These data are evaluated each week to look for any patterns in the reported side-effects that might indicate a potential safety issue, and the reports regularly reviewed by the Joint Committee on Vaccination and Immunisation (JCVI).
Are vaccines tested for safety in diverse groups?
Certain ethnic groups have been underrepresented within clinical trials in the UK. Recent vaccine trials have tried to address this by ensuring participation of ethnic groups at levels similar to those found in the general population. Most vaccines now are developed and used globally with diverse populations, with most vaccines providing similar protection and having a consistent safety profile in all populations.
How were the Covid-19 vaccines approved so quickly?
In the recent Covid-19 pandemic, much of the work on discovery to work out how to make coronavirus vaccines had already been done over the previous two decades, so the research in the pandemic was focussed on the “last mile” of the long development process. The testing process of the vaccines was accelerated by using vaccine platforms (such as mRNA and viral vectors) which could be rapidly scaled and conducting the different trial phases concurrently rather than one after the other. This did not mean corners were cut in terms of safety but the approach instead sped up the way data were gathered. These ended up being some of the largest clinical trials of vaccines ever done, typically with 25,000-40,000 people taking part in the phase three trials.