It comes after a decision made by the Joint Committee on Vaccination and Immunisation (JCVI) to offer an alternative vaccine to under 30s, as the risk of Covid-19 is lower in that age group and is outweighed by the very small risk of blood clots.
This decision has now been extended to under 40s, who are still to be reached by the vaccination programme in Scotland.
The JCVI has advised that another vaccine should be offered to under-40s without underlying health conditions where an alternative is available, and as long as it does not cause any substantial delays to the vaccination programme.
Urging people to accept vaccines, it has warned that reductions in uptake or speed of jab deployment will increase the size of any third wave of infection in the UK.
For this reason, it believes any vaccine would be better than no vaccine, even for those under the age of 40.
However, there are thought to be no supply issues with offering the vast majority of younger people alternatives to AstraZeneca.
Professor Wei Shen Lim, Covid-19 chairman for JCVI, said: “Safety remains our number one priority.
“We have continued to assess the benefit/risk balance of Covid-19 vaccines in light of UK infection rates and the latest information from the MHRA on the extremely rare event of blood clots and low platelet counts following vaccination.
“As Covid-19 rates continue to come under control, we are advising that adults aged 18 to 39 years with no underlying health conditions are offered an alternative to the Oxford/AstraZeneca vaccine, if available and if it does not cause delays in having the vaccine.
“The advice is specific to circumstances in the UK at this time and maximises use of the wide portfolio of vaccines available.
Up to April 28, the MHRA had received 242 reports of blood clots accompanied by low blood platelet count in the UK, all in people who had the AstraZeneca vaccine, out of around 28.5 million doses given.
These clots occurred in 141 women and 100 men aged from 18 to 93, with 49 deaths. Six cases have been reported after a second dose.