Understanding Risk:Benefit

What is meant by risk:benefit?

No medicine or vaccine is ever entirely risk-free. When evaluating a medicine or vaccine, it is important to consider both the benefits and risks, including both the risk of receiving the medicine or vaccine and of not receiving them.

The benefits of a medicine are its positive effects (e.g., preventing serious illness or death, reducing pain or protecting from infection). The risks are the unwanted or unexpected effects, that can span from relatively minor to rare or more serious events.

How is risk:benefit assessed?

All medicines and vaccines are constantly evaluated for safety and to ensure that benefits outweigh any potential risks. These reviews start in the early stages of medicine development, through to regulatory assessments for approval and ongoing safety monitoring in the ‘real-world’.

Rigorous testing and clinical trials

All medicines and vaccines go through rigorous testing before they can be approved for use by independent regulators across the world. Evaluating risk:benefit starts with extensive safety tests in a laboratory, through to small and then large-scale clinical trials, each stage building greater confidence in its safety profile.

Reviews by regulatory authorities

Regulators assess and approve medicines based on the benefits outweighing the known risks. This assessment is informed by extensive evidence on the efficacy and safety of a medicine. Regulators also consider factors such as the severity and impact of the condition the therapy is designed to treat, and the current unmet needs of patients.

Ongoing monitoring in the ‘real-world’

Following approval for use by regulatory authorities, ongoing safety monitoring procedures ensure all medicines are continuously reviewed for ‘adverse’ or unwanted effects, and that the benefits continue to outweigh any risks.

This monitoring – called “pharmacovigilance” – considers reports from people who receive the medicine or vaccine, and health care professionals, which are then submitted to health authorities. Pharmacovigilance is a routine part of medicine development and regulation. This helps researchers to learn more about the impact of medicines and vaccines in the ‘real-world’, and health authorities keep the public as safe as possible.

How are vaccines assessed for risk:benefit?

All vaccines are rigorously tested in clinical trials before approval for use, and then continuously monitored for safety once they’re being used. The standard of testing and monitoring of vaccines is higher than it is for most other medicines, as vaccines are generally administered to healthy people.Vaccines remain the most cost-effective protection against viral infections and are an important tool to help save lives.2

Have the COVID-19 vaccines been assessed for risk:benefit?

The COVID-19 vaccines were extensively tested in clinical trials with tens of thousands of people.

Globally, tens of millions of people have now been vaccinated against COVID-193 and they have helped save thousands of lives already.4 With this, our understanding of how effective vaccines are at reducing the burden of and protecting against the virus in the ‘real world’ continues to grow.

Comprehensive safety monitoring procedures will continue for all COVID-19 vaccines, with thorough scrutiny from pharmaceutical companies, regulators, scientific and medical experts.


1.Vaccine Knowledge Project. How vaccines are tested, licensed and monitored. Available at https://vk.ovg.ox.ac.uk/vk/vaccine-development. Last accessed May 2021.

2.The World Health Organization (WHO). Bulletin of the World Health Organization - Vaccination greatly reduces disease, disability, death and inequity worldwide. Available at https://www.who.int/bulletin/volumes/86/2/07-040089/en/. Last accessed May 2021.

3. Our World in Data. Statistics and Research. Coronavirus (COVID-19) Vaccinations. Available at https://ourworldindata.org/covid-vaccinations. Last accessed June 2021.

4. Public Health England. COVID-19 vaccine surveillance report Week 22. Available at https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/991104/Vaccine_surveillance_report_-_week_22.pdf. Last accessed June 2021