Revised: 21 November 2023

Safety Information

How Does Medsafe Monitor Medicine Safety?

Suspected adverse reaction reports
Assessing safety signals
Taking action
Communicating safety information
Further information and definitions

Medsafe uses a variety of methods to monitor the safety of medicines and vaccines after they have been approved for use in New Zealand. These activities are known as pharmacovigilance.


Pharmacovigilance is the science and activities relating to the detection, assessment, understanding and prevention of adverse events or any other medicine-related problem.

The main aim of pharmacovigilance is to identity safety signals of possible problems with a medicine or vaccine.

Pharmacovigilance involves:

  • monitoring the use of medicines and vaccines in everyday practice to detect previously unrecognised side effects or changes in the patterns of side effects
  • assessing the risks of benefits and harm of medicines and vaccines
  • taking action when required to improve the safety profile of medicines and vaccines
  • providing information to healthcare professionals and consumers to promote the safe use of medicines and vaccines
  • monitoring the impact of any action taken and assessing whether further regulatory action is required.

We use information from many sources for pharmacovigilance, including:

  • clinical and observational studies
  • published medical literature
  • pharmaceutical companies
  • other regulatory authorities, such as the Food and Drug Administration (USA), the European Medicines Agency (Europe) and the Therapeutic Goods Administration (Australia)
  • suspected adverse reaction reports (described further below).

Suspected adverse reaction reports

Adverse reactions (side effects) are harmful effects suspected to be caused by a medicine or vaccine. We encourage healthcare professionals and consumers to report suspected adverse reactions. Pharmaceutical companies also submit reports of adverse reactions associated with their medicines or vaccines.

Medsafe collects and processes suspected adverse reaction reports and the physicians at the Centre for Adverse Reactions Monitoring (CARM) medically assess non-routine reports.

Report a suspected adverse reaction to a medicine or vaccine

Reporting suspected adverse reactions contributes to medicine safety

Before a medicine or vaccine is marketed, any experience of its safety and efficacy is limited to its use in clinical trials. However, clinical trials do not always reflect the actual use of a medicine or vaccine in real life. For example, a medicine or vaccine may only be tested in a relatively small number of people for a limited length of time.

Although Medsafe may receive extensive information from clinical trials for a specific medicine or vaccine, some adverse reactions are rare and may not be seen until a very large number of people have used the medicine or vaccine. For this reason, it is very important to monitor all medicines and vaccines after they are marketed.

Suspected adverse reaction reports are an important contribution to the safety monitoring of medicines and vaccines in New Zealand by enabling Medsafe to quickly detect and respond to possible safety signals.

Advantages and limitations of suspected adverse reaction reports

Suspected adverse reaction reports are a very quick and effective way of detecting safety signals with medicines and vaccines. They are used to monitor the safety of medicines and vaccines in real life, over the lifetime of the medicine or vaccine, and for all types of people.

However, suspected adverse reaction reports have limitations including:

  • under-reporting (ie, some cases may not be reported)
  • a lack of reliable information on the number of people taking the medicine
  • incomplete information on diagnosis and history of the patient
  • not very effective at detecting adverse reactions that occur a long time after starting the medicine.

Due to these limitations, suspected adverse reaction reports are only used to detect safety signals and are not used to investigate or confirm them.

Information obtained from suspected adverse reaction reports need to be interpreted with caution.

Search for suspected adverse reactions to medicines and vaccines reported in New Zealand

Assessing safety signals

Medsafe analyses adverse reaction reports together with other information to confirm if a safety signal is real. We seek advice from independent experts via the Medicines Adverse Reactions Committee (MARC) or we may form working groups of experts to provide advice. We also work closely with other regulatory authorities from around the world.

Medsafe performs a risk-benefit assessment on safety signals to assess whether any action is required. Most safety signals can’t be confirmed due to insufficient evidence and so we don’t take any action. However, we may continue to closely monitor the issue and reassess it as more evidence becomes available.

A small number of safety signals are confirmed to be real. In these cases, Medsafe takes appropriate action to improve the safety profile of the medicine or vaccine.

Taking action

If a safety concern is confirmed, Medsafe can take the following actions.

  • Provide information directly to healthcare professionals and consumers (described further below).
  • Require warnings in the medicine data sheet or on the packaging.
  • Restrict the conditions that the medicine or vaccine can be used for.
  • Recommend a change to the legal status of a medicine or vaccine. For example, change the classification of a medicine from over-the-counter to prescription-only.
  • Ask the pharmaceutical company to do a clinical study to investigate a particular safety concern.
  • In rare circumstances, Medsafe can recommend removal of a medicine or vaccine from the market.

Communicating safety information

Medsafe communicates safety information to healthcare professionals and consumers in a variety of ways.

Further information and definitions

For more information about the known adverse reactions for your medicine or vaccine, see the consumer medicine information (CMI), the medicine box or packaging, the data sheet, or ask your healthcare professional.

Neither Medsafe nor CARM can say that a medicine or vaccine caused a suspected adverse reaction in an individual. If you have concerns about a medicine you are taking, please speak to your healthcare professional.


Adverse event: Unwanted and sometimes harmful outcomes that happen after using a medicine or vaccine. For vaccines, they are often referred to as adverse events following immunisation (AEFIs). An adverse event does not mean that the medicine or vaccine caused the event. Adverse events include adverse reactions (side effects).

Adverse reaction: A harmful effect suspected to be caused by a medicine or vaccine. They are also known as adverse drug reactions (ADRs), side effects or undesirable effects.

Safety signal: A safety signal is an indication that there may be a safety problem related to a medicine or vaccine. This could be a previously unknown side effect or a change in the frequency or severity of a known side effect.

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