Covid immunity starts to wane six months after getting a second vaccination, a study has found.
Experts said research carried out on thousands of healthcare workers has reinforced the need for booster jabs.
The study found double-jabbed people who had previously been infected had greater protection against the virus, standing at over 90 per cent after two doses.
This protection remained strong over a year after infection.
For people who have had covid but no subsequent vaccination, protection against the virus was 69 per cent after one year.
The world's largest study of its kind, led by the UK Health Security Agency (UKHSA), involves 35,768 health workers - 6,000 from Scotland.
Glasgow Caledonian University Professor Lesley Price is leading the Scottish arm of the UK-wide study analysing Covid immunity among hospital-based healthcare workers.
She is working in partnership with 10 health boards, Public Health Scotland (PHS), the Scottish Chief Scientist Office, NHS Research Scotland and the Scottish Government.
Professor Price said: "There are two key messages for the public from the latest findings of the study.
"The first is that since immunity starts to wane at six months, it reinforces the need for booster jabs.
"The second is that if you have had the infection and had your vaccinations, your immunity should be the stronger, so people still need to be vaccinated to get the best protection.
"Some members of the public think they don't need vaccines because they have had the infection and have natural immunity.
"In people who have had COVID-19 infection, but no subsequent vaccination, protection against the virus was 69 per cent after one year.
"One of the things we didn't know when we started the vaccination programme was how long protection would last for and this new research paper addresses that question.
"We need to keep monitoring people's immune response to the booster so that the Government can make appropriate decisions about their future vaccination strategy.
"The importance of this has been recognised with the study now continuing to follow up its participants for up to two years."
The analysis was carried out during the Delta variant period and before the emergence of Omicron.
Further work is ongoing to investigate the protection to Omicron infections provided by prior infection and vaccination.
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