The Scottish government is urging over-40s to book their second COVID jab as soon as possible.
Anyone in that age group with a scheduled appointment more than eight weeks after their first jab is being told to book an earlier slot.
It comes as the Joint Committee on Vaccines and Immunisations (JCVI) has recommended shortening the interval between jabs from 12 to eight weeks.
But the Scottish government said many people over-40, in particular, have received an invitation to book a slot in line with the previous recommendation of a 12-week interval.
The push for people to book sooner appointments comes as the Delta variant, which was first identified in India continues to spread in the UK.
As well as the "vaccine journey" tool on the NHS Inform website, the national helpline can be used to reschedule second doses.
Health Secretary Humza Yousaf said: "We are working closely with NHS boards to ensure the number of appointments can be increased in line with national guidance to help combat new variants and provide protection to as many people as possible.
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"Boards are boosting their capacity to administer second doses alongside the delivery of first doses to younger cohorts and appointments are now being issued in accordance with the new recommendation of an eight-week gap.
"The second dose is vital in providing greater and longer-lasting protection against the virus - particularly the new Delta (Indian) variant.
"In line with the advice from the JCVI, we encourage those whose appointment was already scheduled - which is mainly over-40s at this time - to use the NHS Inform online tool, drop-in clinics or the national helpline to get their second dose appointment as close to eight weeks after their first as possible."
Just over half of those aged 18 or over in Scotland have received both jabs, according to Scottish government figures.
Meanwhile, more than 77% of Scottish adults have received either the first dose or both doses of the vaccine.
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