51����

The UK government’s chief scientific adviser has urged extreme caution about reading too much into preliminary data from Israel on the extent to which covid-19 vaccines reduce transmission of the coronavirus.

Patrick Vallance said that while early showed a drop of up to 60 per cent in the spread of infections after people had been given Pfizer and BioNTech’s vaccine, more research is needed. “I think we’ve got to be extremely cautious and wait until we’ve got proper data,” he told 51���� at a Downing Street briefing on 27 January.

Covid-19 vaccine trials tested them for safety and their efficacy in reducing severe illness, but not on how much they cut transmission, a question that is still urgently being explored. Of the UK’s vaccine roll-out and its impact on the virus’s spread, Vallance said: “It’s too early to say what’s happening in the UK. It’s being looked at very, very carefully.”

Jonathan Van-Tam, the deputy chief medical officer for the UK government, echoed Vallance’s view at the briefing. “I don’t think there are clear data on whether vaccines reduce transmissibility,” he said. Nonetheless, he said they should have some effect on transmission. “The question is less will they, but to what extent,” he said.

Van-Tam confirmed that Public Health England is undertaking studies on the issue, and the first data would be on vaccines’ impact on UK infections, followed by hospitalisations and deaths. “I know everyone is straining to get some information, and we just can’t get it any faster,” he said.

To date, . However, the daily number of vaccinations dropped this week to a rate that would leave the UK government off track on its target of nearly 14 million vulnerable people being vaccinated by 15 February.

Asked why the numbers had fallen, prime minister Boris Johnson and Vallance suggested the issues were vaccine supply and regulatory checks.

“Don’t forget that these are vaccines that have only just been invented and the batches are only just being approved. One of the things we said at the beginning is there would be bumps, up and down, particularly in these early phases, as production gets under way,” Johnson told 51����.

Vallance added: “On the lumpiness of supply, this isn’t making widgets. These are complex, quality-controlled biological processes. It’s not surprising supply goes up and down – there will be changes week on week.”

The comments came as the UK government said it would publish a “route map” out of lockdown restrictions on 22 February, and that schools in England would not reopen until 8 March at the earliest.

Sign up to our free Health Check newsletter for a round-up of all the health and fitness news you need to know, every Saturday