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Ethical and policy considerations for COVID-19 vaccination modalities: delayed second dose, fractional dose, mixed vaccines
  1. Jonathan Wolff1,
  2. Caesar Atuire2,
  3. Anant Bhan3,
  4. Ezekiel Emanuel4,
  5. Ruth Faden5,
  6. Prakash Ghimire6,
  7. Dirceu Greco7,
  8. Calvin W L Ho8,
  9. Sonali Kochhar9,10,
  10. Surie Moon11,
  11. Owen G Schaefer12,
  12. Ehsan Shamsi-Gooshki13,
  13. Jerome Amir Singh14,15,
  14. Maxwell J Smith16,
  15. Beatriz Thomé17,
  16. Aissatou Touré18,
  17. Ross Upshar19
  1. 1Blavatnik School of Government, Oxford University, Oxford, UK
  2. 2Philosophy and Classics, University of Ghana, Accra, Greater Accra, Ghana
  3. 3Centre for Ethics, Yenepoya University, Mangalore, Karnataka, India
  4. 4Department of Medical Ethics and Health Policy in the Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
  5. 5Berman Institute of Bioethics, Johns Hopkins University, Baltimore, Maryland, USA
  6. 6Department of Microbiology, Tribhuvan University, Kirtipur, Kathmandu, Nepal
  7. 7Professor Emeritus, School of Medicine, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
  8. 8Department of Law, and Centre for Medical Ethics and Law, University of Hong Kong, Pok Fu Lam, Hong Kong
  9. 9Global Healthcare Consulting, New Delhi, India
  10. 10Department of Global Health, University of Washington, Seattle, Washington, USA
  11. 11Law, Graduate Institute of International and Development Studies, Geneve, Switzerland
  12. 12Centre for Biomedical Ethics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
  13. 13Medical Ethics and History of Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran
  14. 14Howard College School of Law, University of KwaZulu-Natal, Durban, KwaZulu-Natal, South Africa
  15. 15Division of Clinical Public Health, Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
  16. 16Preventive Medicine Department, Faculty of Health Sciences, University of Western Ontario, London, Ontario, Canada
  17. 17Federal University of São Paulo, São Paulo, Brazil
  18. 18Indpendent consultant, Dakar, Senegal
  19. 19Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
  1. Correspondence to Professor Jonathan Wolff; jonathan.wolff{at}

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  • A number of countries are considering administering COVID-19 vaccines in ways that have not been informed by clinical trials, nor recommended by the manufacturers or authoritative international health bodies, in order to provide some protection for a greater number of people under conditions of vaccine scarcity, or for other reasons.

  • Proposals include delaying the second dose of two-dose vaccines beyond the period for which there is evidence from clinical trials, or foregoing it entirely, giving fractional doses, providing vaccines for individuals outside recommended age ranges, or providing different vaccines for the first and second, or booster, doses.

  • The WHO Strategic Advisory Group of Experts on Immunization Values Framework provides a valuable ethical background for considering the policy questions concerning choice of vaccine modalities, highlighting that vaccines are a global public good for the benefit of all, and drawing on values of human well-being, equal respect, global and national equity, reciprocity and legitimacy.

  • This paper considers the factors that we believe governments have an ethical duty to take into account in considering the vaccination modality they adopt.

  • In developing their policies, governments must take seriously the evolving scientific evidence base, as well as potential effects on public trust, the legitimate expectations and rights of those who have been begun the vaccination process, responsibility to the global community and equity, among others considersations, and to communicate their reasons for their decisions appropriately to the affected populations.

  • Any decision to adopt a modality that differs from those recommended by manufacturers must be accompanied by comprehensive and clear mechanisms to follow-up those in alternative modalities.


As a growing number of vaccines for COVID-19 gain emergency use designation, including emergency use authorisation and conditional marketing authorisation under different jurisdictions, the WHO Strategic Advisory Group of Experts on Immunization (SAGE)1 has issued a number of …

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