People as young as 25 can now join the reserve list for a coronavirus vaccine in the Cwm Taf Morgannwg University Health Board area.
It means that people aged between 25 and 49 will now be offered appointments for a first dose at short notice whenever there are "no shows" to ensure no vaccines go to waste.
Until now only people aged 35 and over could apply (35-49), but as the health board continues to vaccinate 40-49 year olds with their first dose, it can now invite others to be on standby should an appointment become available.
Eligible people must be aged between 25-49, live in Cwm Taf Morgannwg - which covers Rhondda Cynon Taf, Merthyr Tydfil and Bridgend - or be registered with a Cwm Taf Morgannwg GP. To get your name on the reserve list please click this link.
Some 345,500 vaccines have been administered in the Cwm Taf Morgannwg area to date, with more than 90,000 people now fully vaccinated having received both doses.
A spokesperson for the health board added: "Cwm Taf Morgannwg has a cancellation or rescheduling form online for anyone who does not wish to take up the offer of a vaccine, cannot make their appointment, or needs to book a new date. You can find it here.
"Anyone in priority groups 1-9 who is yet to hear from the health board should contact us urgently. You can find the form on CTM's vaccine page on its website here."
Earlier this month the online vaccine reserve list for the area crashed when 13,000 people aged 40-49 tried to access it at the same time.
Covid infection rates have dropped dramatically across the region in recent weeks, with Merthyr Tydfil recording the lowest of any local authority (3.3 per 100,000 population) in Monday's figures published by Public Health Wales.
Currently, GPs in Cwm Taf Morgannwg are offering second doses only to patients who received a first dose at their surgery.
The health board's six community vaccination centres are offering first and second doses.
