Question & Answer

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

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  • ‘COVID-19 vaccines are medicines that prevent disease caused by the novel coronavirus SARS-CoV-2 by triggering an immune response (European Medicines Agency (EMA)).
  • Claims have circulated through the media that COVID-19 vaccines are unsafe because they were developed quickly.
  • COVID-19 vaccines were developed following the same safety requirements as any other vaccine in the EU (EMA).
  • COVID-19 vaccines are first tested in laboratories and are then tested on human volunteers in clinical trials Clinical trials are a type of research that examine new treatments and their effects on human health (World Health Organisation).to make sure they are safe and effective before they are approved for public use by regulatory bodies.
  • The role of regulatory bodies, like the EMA and The Health Products Regulatory Authority in Ireland (HPRA) is to ‘make sure that medicines are as safe as possible and do what they are intended to do’. These bodies found that the ‘COVID-19 vaccines are safe and effective’ (CDC).
  • There are currently four COVID-19 vaccines approved for use in the European Union, Pfizer-BioNTech, AstraZeneca, Johnson & Johnson and Moderna.
  • Individual clinical trials by Pfizer-BioNTech, AstraZeneca, Johnson & Johnson and Moderna, and systematic reviews of  the available evidence, found that COVID-19 vaccines are effective and safe.
  • Short-term symptoms like mild to moderate pain at the injection site, tiredness and headaches were the most common side effects reported.
  • Even after a COVID-19 vaccine is approved, independent bodies such as the HPRA (Ireland) and the EU pharmacovigilance system stay involved, and continue to monitor safety. For example, the AstraZeneca and Johnson & Johnson vaccines were recently examined by the EMA’s safety committee, PRAC, after individual European countries voiced safety concerns.  The committee found that ‘the benefits of the vaccine continue to outweigh the risks for people who receive it’.  However, the committee did advise ‘that unusual blood clots with low blood platelets (platelets are essential for normal blood clotting) should be listed as very rare side effects of Vaxzevria (formerly COVID-19 Vaccine AstraZeneca)’.
  • In response to the PRAC committee findings, the National Immunisation Advisory Committee (NIAC, Ireland) recommended (27th April) that both the Johnson & Johnson and AstraZeneca vaccines should be used for people over 50 years of age and over.

How was it possible to develop COVID-19 vaccines so quickly?

  • The development of vaccines for COVID-19, a new strain of the coronavirus, was supported by years of ongoing research to develop vaccinations for other types of coronaviruses e.g. the SARS virus (severe acute respiratory syndrome) and MERS-CoV (Middle East respiratory syndrome coronavirus).
  • ‘Unprecedented scientific collaborations have allowed COVID-19 vaccine research, development, and authorisations to be completed in record time – to meet the urgent need for COVID-19 vaccines while maintaining high safety standards’.
  • The high number of new cases of COVID-19 across the world meant the vaccine trials could quickly assess the safety and effectiveness of the vaccines. Vaccine development is expensive. With COVID-19 vaccines, there was huge, global investment into their research.

Things to Remember


  • Lead Researcher: Dr Elaine Finucane, HRB-Trials Methodology Research Network, School of Nursing and Midwifery, NUI Galway.
  • Reviewed by: Professor Declan Devane, School of Nursing and Midwifery, HRB-Trials Methodology Research Network, Evidence Synthesis Ireland & Cochrane Ireland, NUI Galway
  • Evidence Advisor: Professor Patrick Mallon, Centre for Experimental Pathogen Host Research, University College Dublin and Consultant in Infectious Diseases, St Vincent’s University Hospital, Dublin. 
  • Evidence Advisor: Anne Daly, PPI Ignite, NUI Galway
  • Journalist Advisor: Dr Claire O’Connell, Journalist, Contributor, The Irish Times