Safety of Medicines

Our commitment to medicine safety begins in the research laboratory and continues for as long as the medicine is prescribed to patients anywhere in the world.


Safety of medicines

Receiving regulatory approval for a medicine is a judgement on the safety of a medicine, but it is not the final safety checkpoint. Pre-registration clinical trials cannot detect every possible side effect, and more may become apparent when the medicine is used:

  • in much larger groups of patients
  • for longer periods of time – sometimes for months or years
  • in a more diverse patient population
  • under ‘real-world’ circumstances rather than the more predictable and closely monitored conditions of clinical trials

It is very important to assess how medicines act in real-world patients, who are not as closely monitored and supervised as participants in clinical studies. In the real world, patients:

  • don’t always take their medication as recommended
  • don’t always adhere to dosing recommendations
  • may have underlying conditions that may affect how the medication works
  • may take other medication, including non-prescription medication

These types of different conditions provide the opportunity to build up knowledge which may go beyond what was known about the safety characteristics of the medicine at the time of approval.


Monitoring safety

Patient safety is our first priority. We encourage healthcare professionals and patients to report any ‘adverse events’ (side effects) experienced while taking a Pfizer medicine, regardless of whether it is thought the event was caused by our medicine or not. We also encourage reporting if the medicine does not work as expected.

We have legal and ethical responsibilities to collect and analyse reports of adverse events. Appropriate reports are sent to the regulatory authorities within defined timelines. All Pfizer employees play a critical role in meeting these responsibilities and are fully trained in how to recognise and report an adverse event.

In the UK, the Medicines and Healthcare products Regulatory Agency (MHRA) is responsible for regulating all medicines and medical devices, ensuring they work and are acceptably safe.

Through its Yellow Card Scheme the MHRA monitors the safety of the medicines and vaccines on the market. Whenever there is a suspicion that a medicine - or combination of medicines - has caused a side effect, the MHRA asks patients and healthcare professionals to complete a Yellow Card.

These reports are then evaluated alongside other information such as clinical trial data, medical literature or data from international medicines regulators, to identify previously unrecognised side effects.

If a new side effect is identified, information is carefully considered in the context of the overall side effect profile for the medicine, and how the side effect profile compares with other medicines used to treat the same condition.

The MHRA takes action, whenever necessary, to ensure that medicines are used in a way that minimizes risk, while maximising patient benefit.

In assessing the safety of medicines, the MHRA is advised by the Commission on Human Medicines (CHM), which is the Government’s independent scientific advisory body on medicines safety. The CHM is made up of experts from a range of health professionals and includes lay representatives.

Newly identified safety issues help us, working with regulatory agencies, to better understand who should or should not take the medicine, or how to update dosing recommendations.


PP-PFE-GBR-4007 / October 2021