NHS Shetland is remaining focused on ensuring the coronavirus vaccines are rolled out by May.
But the nationwide shortage in supply means the health authority to hold off on unveiling a third mass vaccination centre in Scalloway.
It follows news national supplies of Pfizer and AstraZeneca were slowing down.
Interim director of community health and social care Brian Chittick is leading the roll-out of the vaccine in the isles.
He said NHS Shetland was lacking in sufficient vaccine supply to run the planned Scalloway centre next week, which will operate alongside the two existing mass vaccination units in Lerwick.
“The due date we’ve given our infrastructure teams is 1st March to open up that facility in Scalloway.
“That is still doable, but we feel at the minute that the vaccine supply that we have that to open up three centres and have them operational on a daily basis, we just don’t have the vaccine supply to do that.
“So at the minute we will just be opening up the mass vaccination centres completely in alignment with what vaccine we’ve got available.
“Whilst the Scalloway sports hall will be ready as a mass vaccination centre, it may not be used in the next fortnight or so until we get our vaccine supply a little bit smoother.”
He said NHS Shetland was in conversation with the Scottish government to “flag” where weekly supplies are.
Mr Chittick said the health board was looking closely at administering second doses of the vaccine to ensure it could meet Scottish government guidelines.
He said at the moment the focus was on giving first doses to unpaid carers and those with underlying health conditions between the ages of 16 and 64.
But Mr Chittick added the aim remained to have all those receiving the vaccine given one by early or mid-spring.
“We’ve got with the new mass vaccination centre coming online, certainly the capability to vaccinate over 5,000 people a week which would make tidy business of vaccinating those people we want to do.
“But that’s completely dependent on the vaccine flow in Shetland.”