A single vaccine dose offers as much if not more protection for people who were previously on the shielding list as it does for the rest of the population, a study has found.

Research led by Public Health Scotland and supported by the University of Edinburgh, examined the effectiveness of the vaccine using data from more than 100,000 people to determine its impact on reducing severe Covid-19 among those designated as clinically extremely vulnerable.

Cancer patients were among those advised to take extra precautions during the first few months of the pandemic amid evidence they are six times more likely to become seriously ill.

There were some concerns that a weakened immune system may reduce the effectiveness of Covid vaccines.

The study - which has not yet been peer reviewed -found that the efficacy of a single vaccination dose in protecting against severe Covid-19 was as high or higher in those eligible for shielding as in those without risk conditions.

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However, it concluded that more research is needed to determine the efficacy of the vaccine amongst transplant patients.

Patients deemed extremely clinically vulnerable will be among those receiving booster vaccinations later this year.

Dr Nicholas Phin, Director of Public Health Science at Public Health Scotland, said: 

“Those that are considered clinically extremely vulnerable are about six times more likely to experience severe Covid-19 leading to hospitalisation or death, than someone the same age without their condition.

“The results of this study are therefore hugely encouraging in showing that vaccination amongst this group does provide substantial levels of protection against COVID-19.

"This should bring welcome news to those who are at most risk across the country.

“However, caution is still needed. Restrictions continue to ease and case rates remain high, meaning that all people, especially those who are at most risk, should continue to take extra precautions until fully vaccinated with two doses.”

Co-author of the study, Professor Helen Colhoun of the Institute of Genetics and Cancer at University of Edinburgh, said: “Through using a pre-existing register that had been used to determine the eligibility for the national shielding support programme, we were able to identify those with certain conditions or on certain drugs that were likely to lead to extreme vulnerability.

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“We found that in most categories of vulnerability, the vaccine was highly effective in reducing the risk of severe Covid-19.

"However, for those who have received a solid organ transplant, there was not enough data to demonstrate the vaccine’s effect due a low number of people in this group, meaning further studies are needed.

“In the meantime, we would still encourage recipients of organ transplants to get fully vaccinated if they have not done so already.”

Deputy Chief Medical Officer Nicola Steedman said: "This study is a much needed insight into the effectiveness of coronavirus vaccination for many of those thought to be at highest risk of suffering serious consequences from the virus.

“Although additional studies in larger populations are needed for solid organ transplant recipients, the results are very reassuring in terms of efficacy of vaccination in other high clinical risk individuals, including those who are immunocompromised.”

“While full details of the Covid booster vaccination programme are still to be finalised, we expect this will begin with those at highest risk this autumn, with our preparations already firmly underway for that.

“Around 96% of those on the highest risk list in Scotland have received at least one dose of vaccination and 93% have received both doses. We urge any of those who haven’t yet come forward to be vaccinated to do so now if you are able.”