Scientific evidence recommending delaying second dose of COVID-19 vaccination: FOI release

Information request and response under the Freedom of Information (Scotland) Act 2002.

Information requested

What/where is the evidence that delaying the second dose for 12 weeks against the makers instructions will carry the same protection as if done in the correct time frame?


The Joint Committee on Vaccination and Immunisation (JCVI), an independent clinical group of experts that provides all Governments in the UK with advice on vaccinations, recommended that the second vaccination dose for both the Pfizer BioNTech and AstraZeneca COVID-19 vaccines should be between three or four and twelve weeks from the first dose - JCVI issues advice on the AstraZeneca COVID-19 vaccine - GOV.UK (

This is in recognition of the very high levels of protection offered from the first dose, and that the increased transmission rate of the new strain of coronavirus poses a significant risk of increased case numbers and subsequent deaths. Simply put, their advice will maximise the lives that can be saved whilst initially working with a limited supply of vaccine.

The JCVI advice is also supported by the four UK Nations’ Chief Medical Officers (CMOs) as explained in their joint letter - Letter to the profession from the UK Chief Medical Officers regarding the UK COVID-19 vaccination programmes - GOV.UK (

There are further details outlined in a letter from the CMO in Scotland which can be found on the Scottish Government website Coronavirus (COVID-19) - vaccine: letter from the Chief Medical Officer updating on the vaccination programme - 1 January 2021 - ( which covers the timing of second doses, and the statement from JCVI on immunisation prioritisation Joint Committee on Vaccination and Immunisation: advice on priority groups for COVID-19 vaccination (

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