The Pfizer vaccine is 85% effective at preventing people from developing Covid-19 symptoms after the first dose, according a new study from Israel.

The findings, published in the journal Lancet, appear to bolster the UK government's decision to delay the second dose of the Pfizer vaccine - in order to allow more people to receive the jab.

Scientists also found that all infections, including those without symptoms, were reduced by 75% after the first dose.

More than 7,000 healthcare workers at the Sheba Medical Centre in Israel - the country's largest hospital - were involved in the study.

Deborah Dunn-Walters, chairwoman of the British Society for Immunology Covid-19 and Immunology Taskforce, said the findings "should provide reassurance around the UK's decision to offer the two doses of the vaccine 12 weeks apart".

She said the data from Israel offered "the first signs of how effective Covid-19 vaccines are outside of a clinical trial setting and how dosing schedule plays into this".

But she added: "It should be noted that this study was carried out on people of working age, so it will be informative to see a similar study in older people after one dose."

Dr Peter English, a consultant in communicable disease control, described the findings as "good news" but added that available data was "quite limited".