Signs suggest single vaccine dose is reducing Covid positivity rate in UK

There are signs that a single dose of the BioNTech/Pfizer vaccine offers good protection against Covid-19, according to government data on the UK’s vaccination campaign, in further validation of the approach taken to extend the gap between jabs.

Although there is insufficient evidence to draw definitive conclusions about the impact of the vaccination campaign on deaths and hospitalisations in the UK, the data so far suggest it is reducing cases in the groups which have been prioritised to receive the jab, according to several sources with access to government data.

The vaccine appears to be kicking in about two weeks after the jab in younger adults — predominantly healthcare workers — and after about three weeks in the elderly, according to the sources.

The UK government’s decision to extend the gap between first and second jabs of the Covid-19 vaccines from three to 12 weeks to ensure maximum inoculation prompted widespread concern that it might weaken recipients’ immune response. Data from Israel and the UK showing that a single dose confers significant protection after a couple of weeks point to the possibility that the risk has paid off.

Almost all of the data analysed so far relate to the BioNTech/Pfizer vaccine and not the Oxford/AstraZeneca one, as the latter started to be administered three weeks later.

The Sun newspaper reported on Tuesday that Public Health England found that a single dose reduced symptomatic infection by 65 per cent in younger adults and 64 per cent in the over-80s, while two jabs conferred 79 and 84 per cent protection respectively.

However, one senior scientist who has seen the data said it was “misleading to the public to give exact figures at the moment” as the numbers were changing daily and the confidence intervals were too wide.

But he added: “It is looking promising. The delayed second dose strategy is on track at the moment.”

He also noted that it was very difficult to determine the vaccine’s effect on hospitalisations and deaths. 

The PHE findings add to evidence from Israel, released last month, which showed that a single shot of the BioNTech/Pfizer vaccine produced a robust antibody response within weeks.

At the Rambam Health Care Campus in north Israel, 91 per cent of the 1,800 doctors and nurses that received the two-dose vaccine showed a major presence of antibodies 21 days after their first shot and before the second.

At the Sheba Medical Center, similar serological tests at different intervals showed at least 50 per cent of staff with a level of antibodies “above the cut-off point” two weeks after the first jab.

PHE is using a different method to determine whether or not the vaccine is having an impact on case rates in the population, cross-checking Covid-19 testing data with centrally held national vaccination records.

A PHE spokesperson said the body had been analysing the data since the start of the vaccination programme rollout and would publish its findings in due course.