Jabs received by the roughly 1,500 people in Scotland who took part in trials do not show up on the Scottish Government' s vaccine passport app.
But new guidance from the Joint Committee on Vaccination and Immunisation (JCVI) allows for approved vaccines to be given to participants.
Chief medical officer Dr Gregor Smith has written to health boards and letters will also be received by those on vaccine trials outlining how they can request jabs.
"I am extremely grateful to everyone who has taken part in Covid-19 vaccine trials in Scotland for the important contribution they have made in tackling the pandemic," Dr Smith said.
"The Scottish and UK Governments have been working with international partners to agree recognition for Covid-19 clinical trial participants, but there is still currently no internationally agreed policy.
"Allowing participants in trials for vaccines which are not yet authorised in the UK to request another primary vaccination course with authorised vaccines should help to resolve this situation.
"The JCVI has also agreed that those who have participated in clinical trials will be offered a booster vaccination in accordance with the criteria set for the wider booster programme."