Why is Britain delaying second doses of Covid vaccines?

Why have health officials decided to delay giving second doses of Covid-19 vaccines?
According to the Joint Committee on Vaccination and Immunisation (JCVI), modelling of “the high level of protection afforded by the first dose suggests that initially “vaccinating a greater number of people with a single dose will prevent more deaths and hospitalisations than vaccinating a smaller number with two doses”. Delays in giving a second vaccine dose for up to 12 weeks should not affect protection, it is argued. Indeed, it may increase it.

So what protection is offered by first doses of the vaccines?
Short-term efficacy from the first dose of the Pfizer-BioNTech vaccine is around 90%, says the JCVI, while 70% is given for AstraZeneca’s.

Why has the decision to delay second doses angered some doctors and scientists?
Cancelling second-dose appointments has created administrative chaos and upset elderly patients. In addition, some scientists argue that it is not known how the vaccine will perform with an increased gap between injections. Nor is known how protective a single injection is over a longer term. Why take a risk, they say?

Do most scientists share this view?
No. Many say risks of limiting virus protection are low. With a new Covid variant spreading rapidly, vaccinating more people – possibly with less efficacy – is better than giving second doses to fewer people.

What has been the US reaction?
Leading infectious disease expert Dr Anthony Fauci has said that while it was possible to “make the argument” for delaying doses, he would not be in favour. However, commentators have pointed out that the US is highly litigious compared with the UK, so doctors tend to be more cautious about changing vaccine procedures.

How has the UK responded?
Chris Whitty, the chief medical officer of England, and his counterparts in Wales, Scotland and Northern Ireland, have said they back the decision to delay second doses to ensure more people receive their first vaccination as soon as possible.

Where will the vaccine being given to patients?
According to the NHS, there are more than 700 vaccination sites ready to start giving vaccines over the next few weeks. Up to 100 hospitals will come online across the country this week, while another 180 GP services will also begin vaccinations.