Question & Answer

Is the COVID-19 vaccine unsafe because it was developed so quickly?

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  • Claims have circulated through the media that COVID-19 vaccines are unsafe because they were developed so quickly, leading to some people being hesitant to receive the vaccine.
  • COVID-19 vaccines were developed at an unprecedented speed for several reasons, including being able to adapt new technologies from the development of other vaccines and having close collaborations between international regulators, industry and clinical researchers. However, the safety and efficacy (how well it works) requirements for vaccines have not been compromised.
  • The World Health Organization (WHO) declares that ‘all vaccines must undergo rigorous testing in clinical trials to prove that they meet internationally agreed benchmarks for safety and effectiveness’. In addition, they have to be approved for public use by independent regulatory bodies such as the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA).
  • The Health Service Executive (HSE), the WHO and the  Centers for Disease Control and Prevention (CDC) state that COVID-19 vaccines are safe for use.
  • A systematic review of randomised controlled trials suggests that “The safety and tolerance of current COVID-19 vaccine candidates are acceptable for mass vaccination.”
  • Overall, heart muscle inflammation (myocarditis)rates were found to be low in five vaccine safety surveillance studies. The risk was higher among younger male populations, with the onset of symptoms within a few days, usually after the second dose.
  • Another systematic review of studies that looked at pregnancy and neonatal (newborn) outcomes following COVID-19 vaccination did not find an association between vaccines and harmful effects on pregnancy, foetal development, or neonatal outcomes.
  • As with all vaccines, the safety and effectiveness of COVID-19 vaccines continue to be monitored after approval by independent bodies such as the EU pharmacovigilance system, the CDC and the WHO.

Things to Remember


  • Lead Researcher: Dr. Petek Eylül Taneri, Post-Doctoral Researcher, University of Galway
  • Reviewed by: Prof. Declan Devane, Professor of Health Research Methodology, Deputy Dean, College of Medicine, Nursing and Health Sciences, University of Galway; Scientific Director, HRB-Trials Methodology Research Network; Director, Evidence Synthesis Ireland. Director, Cochrane Ireland.
  • Topic Advisor: Dr. Liam Glynn, Professor of General Practice at the Graduate Entry Medical, School of Medicine, University of Limerick, Chair of the North Clare Primary Care Team and Rural GP.
  • Patient and Public Advisor: Ms Deirdre Mac Loughlin, Public and Patient Involvement in research (PPI) advisor, PPI Ignite, University of Galway
  • Journalist Advisor: Dr. Claire O’Connell, Journalist, Contributor, The Irish Times.

Conflict of Interest Statement: The authors have no financial or other conflicts of interest for this health claim summary.