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Vaccine safety issues at the turn of the 21st century
  1. Laura Conklin1,
  2. Anders Hviid2,
  3. Walter A Orenstein3,
  4. Andrew J Pollard4,5,
  5. Melinda Wharton6,
  6. Patrick Zuber7
  1. 1Global Immunizations Division, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
  2. 2Department of Epidemiology Research, Statens Serum Institut, Kobenhavn, Denmark
  3. 3Emory Vaccine Center, Emory University, Atlanta, Georgia, USA
  4. 4Oxford Vaccine Group, Department of Paediatrics, University of Oxford, Oxford, UK
  5. 5NIHR Oxford Biomedical Research Centre, Oxford, UK
  6. 6Immunization Services Division, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
  7. 7Essential Medicines and Health Products, Organisation mondiale de la Sante, Geneve, Switzerland
  1. Correspondence to Dr Laura Conklin; dvj3{at}


Global gains in vaccination coverage during the early 21st century have been threatened by the emergence of antivaccination groups that have questioned the effectiveness of vaccines to generate public distrust of vaccines and immunisation programmes. This manuscript summarises six key topics that have been at the centre of global discussions on vaccine safety during the early 21st century: thiomersal in multi-dose non-live vaccines, aluminium adjuvants used with several non-live vaccines, autism and auto-immune conditions as possible consequences of vaccination, a risk of immune overload with increasing numbers of vaccinations, and detrimental non-specific effects (NSEs) of vaccination. For each topic, we describe the hypothesis behind the public concern, the evidence reviewed by the WHO’s Global Advisory Committee for Vaccine Safety (GACVS) during 1999–2019, and any significant new data that has emerged since GACVS conclusions were made. Although the scientific evidence on these issues overwhelmingly supports the safety of vaccines, communication messages to caregivers and providers need to condense and convey scientific information in an appropriate way to address concerns contributing to vaccine distrust. In addition, there is need for further studies specifically designed to address both positive and negative NSE of vaccination. The role of GACVS will be increasingly important in evaluating the evidence and engaging the global community in promoting and assuring the safety of vaccines in the decades to come as we move into an era in which we use new vaccination platforms, antigens and formulations.

  • vaccines
  • immunisation

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  • Handling editor Seye Abimbola

  • Contributors LC, AH, AJP, WAO, MW and PZ have all contributed to the content, analysis, write up and review of the manuscript.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

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

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