The study examined the spread of the virus among Israeli healthcare workers and found the vaccine was 85 per cent effective at preventing people developing symptoms after just one dose.
This supports the UK government’s decision to concentrate on giving first dose vaccinations and delaying giving people a second dose until 12 weeks after the first.
The findings, published in the The Lancet, included more than 7,000 healthcare workers from the Sheba Medical Centre in Israel - the country's largest hospital.
Commenting on the research, Deborah Dunn-Walters, chairwoman of the British Society for Immunology Covid-19 and Immunology Taskforce and professor of immunology at the University of Surrey, said: "Due to the high percentage of the Israeli population vaccinated so far, we have been awaiting data from there to indicate the first signs of how effective Covid-19 vaccines are outside of a clinical trial setting and how dosing schedule plays into this."
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.
"Although further research is needed, overall these new findings should provide reassurance around the UK's decision to offer the two doses of the vaccine 12 weeks apart.”
She said that while the study showed patients developed a good level of immunity after one dose, the best and long lasting protection was best after two doses.
"It is critical that all people eligible for Covid vaccination do return to get their second dose when asked to do so by their medical providers."
Dr Peter English, consultant in communicable disease control and former editor of Vaccines in Practice Magazine, described the findings as "good news" but added that available data is "quite limited".
He said: "This is good news. It supports earlier data suggesting that, from six weeks or so after vaccination, vaccine efficacy is likely to be at least 85 per cent - possibly considerably better - at least in vaccine recipients of working age.
"This is a letter, rather than a research paper - as such the data are quite limited, and I would expect far more details to be published in due course."
Dr English added: "As far as I can tell, this particular letter does not include data on severe and mild infection - from other evidence (and experience with vaccination more generally) we would expect the vaccination to be more protective against severe disease than against mild disease, and more protective against mild disease than against asymptomatic infection.
"We may see more information on this when a more complete publication is made available."
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