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Safety of Medicines

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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.


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:

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

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 minimises 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.

PRODUCTSCounterfeit Medicines

What are medicines? What are the risks? How big is the problem?

PRODUCTSReporting Side Effects

What to do if you experience unexpected side effects.

PRODUCTSMedicines Regulation

Our industry is regulated by a number of official bodies who evaluate the quality, efficacy and safety of medicines and vaccines.

PP-UNP-GBR-2976 / December 2022
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