Intended for healthcare professionals

Letters Pfizer covid vaccine dosing interval

Covid-19: No convincing evidence for increasing the vaccine dosing interval

BMJ 2021; 372 doi: (Published 11 February 2021) Cite this as: BMJ 2021;372:n401
  1. Milan Dagli, general practitioner
  1. Ridgway Surgery, Harrow HA2 7DU, UK
  1. daglimilan{at}

The UK government has proposed that, by increasing the gap between covid-19 vaccine doses, they will be able to vaccinate a larger number of people, resulting in greater public health benefit. From a lay perspective, this might seem to make sense. Experience from other vaccines shows that a longer gap can augment the immune response. But this approach belies the fact that we are dealing with very new vaccine technology, of which we have limited practical experience.1

The vaccines have been trialled using specific protocols, and this is the only meaningful experience of their use that we have. There is no convincing evidence for departing from this. The risk of increasing the vaccine gap to 12 weeks is unknown, and we cannot convincingly say that there will be no reduction in efficacy or length of protection or any compromise in safety.

Medicine is all about making decisions and calculated risks in the face of limited or incomplete evidence. Perhaps politics is the same, and the government thinks that this bold decision is the right way to proceed. But this seems too great a risk to take, especially at such a precarious point of the pandemic.

I implore the government to reconsider its approach, err on the side of caution, and focus on ensuring the first four groups on the Joint Committee on Vaccination and Immunisation priority list are vaccinated as per trial protocol.


  • Competing interests: None declared.

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