Delaying Second Dose of COVID-19 Vaccines 'The Right Thing to Do'

Peter Russell

January 07, 2021

The decision to delay second doses of the COVID-19 vaccines to increase uptake of initial immunisation was the right thing to do, experts said.

Prof Andrew Goddard, president of the RCP, said he had "thought long and hard" about the decision but had concluded "it was the right thing to do". Eleanor Riley, professor of immunology and infectious disease at the University of Edinburgh, admitted she had been sceptical initially about the decision but that "the more I thought about it, the more it made perfect sense".

Prof Eleanor Riley/RCP

On December 31, the Joint Committee on Vaccination and Immunisation decided that vaccinating a greater number of people with a single dose would prevent more deaths and hospitalisations than vaccinating a smaller number of people with two doses. It said that efficacy for the Pfizer/BioNTech vaccine against symptomatic COVID-19 following an initial dose was 89% from day 14 after the vaccination was administered.

It also found that the level of protection after a single dose of the AstraZeneca/Oxford vaccine was 73% after 22 days following the first dose.

The JCVI recommended a gap of up to 12 weeks between the first and second doses of both vaccines.

The move was controversial among some scientists and clinicians who pointed out that the wider spacing regimen went against the methods used in clinical trials where doses were administered at 3 or 4 week intervals.

'No Immunological Worries'

Prof Riley told the RCP's 2021 conference that in the case of the AstraZeneca/Oxford vaccine, data showed that "the immunological response with a second dose at 12 weeks is certainly no worse and actually looks really a little bit better than giving an earlier second dose".

She said the results built on research over the last few years on vaccination dosing schedules that suggested "a delayed second dose is frequently beneficial".

Some older vaccination dosing schedules "may have been unnecessarily quick", she added.

However, Prof Riley cautioned that longer intervals between vaccine doses could drive down patient compliance.

"Life gets in the way, people move house, people change jobs, people get other diseases, things happen at home – that means people don't get the letter inviting them for their second dose, or they are just unable to return.

"And the longer you leave it, the bigger the risk is of that."

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