The call to sign up was re-iterated today by NHS Fife as it gears up for the next stage of its mass vaccination programme.
People who miss the deadline will be sent their appointment details by letter at a later date.
The original cut off date of June 4 was extended until the end of the week.
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Ben Hannan chief pharmacist and director of the COVID-19 vaccination programme in Fife said: “The vaccine is our best way out of coronavirus and I’d urge any 18 to 29-year-olds who have not registered to get their appointment details by email or text to do so before the extended deadline.
“The registration process is simple, easy and saves time in getting your vaccine appointment.”
To register by going online at nhsinform.scot/under30register or calling 0800 030 8013.
A survey conducted by the Scottish Government showed that 90 per cent of 18 to 29-year olds will get the vaccine when offered it, with just under seven in ten (69 per cent) eager to get it.
Humza Yousaf, Cabinet Secretary for Health and Social Care, backed the appeal.
He said: “The initial response to the registration online has been really encouraging, and by extending it further we hope to reach more of this age group."“It’s especially helpful for students who are registered with a GP at their term time address to get their appointment details by email or text so they don’t miss appointment letters being sent by post.”