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Balancing benefits and potential risks of vaccination: the precautionary principle and the law of unintended consequences
  1. David Robert Grimes1,2
  1. 1 Dublin City University, Dublin, Ireland
  2. 2 Department of Oncology, University of Oxford, Oxford, UK
  1. Correspondence to Dr David Robert Grimes, Dublin City University, Dublin, Ireland; davidrobert.grimes{at}


Vaccination is a life-saving endeavour, yet risk and uncertainty are unavoidable in science and medicine. Vaccination remains contentious in the public mind, and vaccine hesitancy is a serious public health issue. This has recently been reignited in the discussion over potential side effects of COVID-19 vaccines, and the decision by several countries to suspend measures such as the AstraZeneca vaccine. In these instances, the precautionary principle has often been invoked as a rationale, yet such heuristics do not adequately weigh potential harms against real benefits. How we analyse, communicate and react to potential harms is absolutely paramount to ensure the best decisions and outcomes for societal health, and maintaining public confidence. While balancing benefits and risks is an essential undertaking, it cannot be achieved without due consideration of several other pertinent factors, especially in the context of vaccination, where misguided or exaggerated fears have in the past imperilled public health. While well meaning, over reactions to potential hazards of vaccination and other health interventions can have unintended consequences, and cause lingering damage to public trust. In this analysis, we explore the challenges of assessing risk and benefit, and the limitations of the precautionary principle in these endeavours. When risk is unclear, cautious vigilance might be a more pragmatic and useful policy than reactionary suspensions.

  • public health
  • risk management
  • vaccine-preventable diseases

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  • Contributors DRG has international expertise in the spread of health disinformation and public trust in science. He also advises internationally on science and health policy, chiefly on vaccination and public understanding. DRG is the guarantor of this article.

  • Funding This study was funded by Wellcome Trust (214461/Z/18/Z).

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.