BOOSTER Covid jags should not be routinely administered to the general population because there is no "credible evidence" that protection against severe disease is substantially declining, according to an expert review.

International scientists, including experts from the World Health Organisation and US regulator the FDA, today concluded that vaccine efficacy against severe Covid is so high that booster doses for the general population are not appropriate at this stage in the pandemic - even for the Delta variant.

They stressed that a decline in antibodies over time was not necessarily a signal of waning immunity against severe disease, and that vaccines would "do the most good" by being deployed to countries where few people have had a first dose.

READ MORE: Is Scotland's vaccine passport plan about infection control - or uptake? 

In the UK, the Joint Committee on Vaccination and Immunisation (JCVI) has recommended third doses for around half a million people who have severely weakened immune systems as a result of conditions such as leukaemia, recent organ transplants and HIV/AIDS.

A decision is expected this week on who would be eligible under a wider winter booster programme.

Israel was the first country in to world to begin administering booster shots, with over a million citizens over 60 getting a third Pfizer dose between July 30 and August 22.

Data posted by the Israeli Ministry of Health - which is expected to be peer-reviewed and published in the prestigious New England Journal of Medicine this week - reported that 12 days or more after the booster was given, the relative risk of severe illness was more than 10 times lower.

However, the latest advice on boosters for the general population, published in the Lancet, is based on an analysis of all the currently available evidence worldwide from randomised controlled trials and observational studies published in peer-reviewed journals and pre-print servers.

They said that a consistent finding from the observational studies is that vaccines remain highly effective against severe disease against infections caused by any of the main Covid variants.

On average, they determined that vaccination reduced the risk of severe Covid disease by 95 per cent in relation to both the Delta variant which is now dominant in the UK and the previously dominant Alpha strain, which originated in Kent.

And while vaccines are less effective at preventing asymptomatic infection or transmission, the scientists found that the unvaccinated minority still remained the major drivers of virus spread and were also at the highest risk of serious disease - even in countries with highly-vaccinated populations.

According to the most recent report from Public Health Scotland, the rate of acute hospital admissions for Covid per 100,000 people was highest among unvaccinated individuals in all age groups. 

For example, in the week ending September 3, this ranged from 21 admissions per 100,000 fully vaccinated over-60s compared to 57 per 100,000 in unvaccinated over-60s.

Among 16 to 29-year-olds, the admission rate was 15 per 100,000 in unvaccinated individuals compared to just three per 100,000 for 16 to 29-year-olds who are fully vaccinated. 

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Lead author Dr Ana-Maria Henao-Restrepo, of the WHO, said: “Taken as a whole, the currently available studies do not provide credible evidence of substantially declining protection against severe disease, which is the primary goal of vaccination.

"The limited supply of these vaccines will save the most lives if made available to people who are at appreciable risk of serious disease and have not yet received any vaccine.

"Even if some gain can ultimately be obtained from boosting, it will not outweigh the benefits of providing initial protection to the unvaccinated. If vaccines are deployed where they would do the most good, they could hasten the end of the pandemic by inhibiting further evolution of variants.”

Co-author Dr Soumya Swaminathan, WHO Chief Scientist, added: “Although the idea of further reducing the number of Covid-19 cases by enhancing immunity in vaccinated people is appealing, any decision to do so should be evidence-based and consider the benefits and risks for individuals and society.”

They note that waning antibody levels should not be conflated with a reduction in protection against severe disease as this is also influenced by the presence of T cells and memory B cells in the immune system "which are generally longer lived" than antibodies.

It comes as the UK's four chief medical officers, including Scotland's Dr Gregor Smith, advised ministers to proceed with offering Covid vaccines to all children over 12.

The JCVI previously said it could not recommend the rollout for adolescents on health grounds alone as the benefits were "marginal", but said the CMOs could consider it on a broader criteria such as the impact of the virus on schools and education.