How vaccines are tested, licensed and monitored

How vaccines are tested

Understandably, one of many parents' chief concerns, especially with a new or newly introduced vaccine, is how rigorously and extensively it has been tested. This page aims to give a sense of the process involved in developing and licensing a vaccine for use in the UK.

These are some of the stages a vaccine will have gone through before use:

  • Literature review, theoretical development or innovation
  • Laboratory testing and development
  • Phase I study – an initial safety trial involving a small group of adult participants, to determine dosages.
  • Phase II study – larger group of participants, usually the target group: adults, children, and/or infants, looking at safety and immunogenicity (whether it generates an immune response).
  • Phase III study – even larger group in order to gain statistically significant safety and efficacy data for the SPC (Summary of Product Characteristics). This means looking at whether the vaccine induces a level of immunity that would prevent disease and provides evidence that the vaccine can actually reduce the number of cases.
  • Licensing – expert review of all trial data by the government (MHRA) or European (EMA) regulator. This means that the trials show that the product meets the necessary efficacy and safety levels, and that, for most people, the product’s advantages far outweigh the disadvantages.
  • Phase IV studies – post-marketing surveillance to monitor the effects of the vaccine after it has been used in the population, either requested by regulatory body, or initiated by industry.

The vaccine and the trials used to test it must meet the regulations laid down by the following authorities:

In addition, for trials in the UK, the vaccine and the trial must receive individual approval from the Medicines and Healthcare products Regulatory Agency (MHRA), while the trial itself must be approved from the following authorities:

  • An NHS Research Ethics Committee (find info on their role here )
  • The local NHS Research and Development office, who support and advise researchers in meeting the requirements of local and UK regulatory frameworks (more info on their role here )
  • The Health and Safety Executive (HSE) , for certain types of trials


Who is responsible for monitoring vaccine safety?

Although vaccines undergo rigorous testing prior to licensing for use in the UK, it is important that the safety of vaccines is monitored on an ongoing basis, as with all licensed drugs. This is undertaken by the Medicines and Healthcare products Regulatory Agency (MHRA) through the Yellow Card Scheme. Reports of suspected side effects are sent to the MHRA by drug companies (who are obliged to pass on any reports of suspected side effects that are defined as serious), health professionals, and, since 2005, patients themselves.

What does the MHRA do with these data?

The data are evaluated each week, and the reported side effects are compared against the expected side effects as detailed in the information sheet for the vaccine. If a previously unidentified reaction emerges, or the frequency of reactions is not in line with what is expected, then the MHRA will investigate carefully.

What happens next?

This will depend on the kind of side effect identified, but options include insisting that details of the new side effect are given in the product information leaflet or giving out warnings identifying groups of patients who should not be given the vaccine. In rare circumstances, the vaccine may be withdrawn from use.

Where can I find more information about the Yellow Card Scheme?

You can find detailed information on the scheme here , and data on Yellow Card reports for individual products here .

Page last updated: 
Monday, October 12, 2015