Delays to Covid vaccine shots must be monitored to ensure efficacy, experts say

In order to roll out the available vaccine doses as widely as possible, the decision has been made to delay delivery of the second doses so that a greater number of people will be provided with partial immunity.

The British Society for Immunology (BSI) has said that while it would “prefer” the original dosing schedules tested in the trials to be used clinically, it recognises that health services need to take a pragmatic approach in the short-term to avoid as many deaths as possible.

The current plan is to ensure that the second “booster” dose of both the Oxford-AstraZeneca and the Pfizer/BioNTech vaccines is administered a maximum of 12 weeks after the first instead of the shorter 21-day timeframe recommended in the original trials.

“Close monitoring of the vaccinated population will now be needed in order to garner further evidence,” the BSI said.

BioNTech has told the Financial Times that there is no data to support moves to delay the second dose of the jab. Pfizer had said it only assessed its vaccine on a two-dose regimen, where people were given the jab three weeks apart, and there was “no data to demonstrate that protection after the first dose is sustained after 21 days”.

However, the BSI said that most immunologists would agree that delaying a second booster dose of a protein antigen vaccine (such as the two approved Covid-19 vaccines) by eight weeks “would be unlikely” to have a negative effect on the overall immune response post-boost.

Arne Akbar, BSI president professor, said: “Our country now faces an extremely difficult few weeks with high levels of SARS-CoV-2 circulating within our communities. 

“While our preference is always for an evidence-based approach, we understand the pragmatic approach taken by the Joint Committee on Vaccination and Immunisation in recommending a longer gap between Covid vaccine doses.”

Professor Deborah Dunn-Walters, chair of the BSI’s Covid-19 and Immunology Taskforce, said: “With the change to Covid-19 vaccine dosing schedules and with the number of Covid-19 cases and deaths increasing at a significant rate, the British Society for Immunology has made several recommendations to ensure that the vaccine rollout has the maximum impact in saving lives.

“This includes implementing a robust programme of immune monitoring to assess how changing the dosing schedule of the two Covid-19 vaccines impacts efficacy.

“Clear communication is key and we encourage the Government to run a high-profile, multifaceted engagement programme to further build public understanding of Covid-19 vaccination.

“As well as answering the public’s questions around Covid-19 vaccination, it is crucial that a strong message is heard by all that the timing of the vaccinations may have changed, but it is still critical to receive two doses to gain optimum protection from Covid-19 disease.”