Around 67,000 people across Northamptonshire are still to get a Covid-19 booster jab after a slump in demand since Christmas.
The county's vaccination programme director fears public messages about the Omicron variant 'not being that serious' may be hindering the rollout.
Chris Pallot said: "We're not as busy as we would hope to be — still busy but nothing like we were at beginning of the booster programme in December, just after the Prime Minister made his big announcement.
"In the next seven days we've got 5,100 bookings in slots and there are 24,000 slots available — which is great news for 67,000 under age of 49 who are still to come forward to have their booster.
■ Click HERE for up-to-date details on how and where to get a first, second or booster Covid jab in Northamptonshire this weekend
"Demand has dropped off but we know a lot of people have had the virus since Christmas and because the 28-day period people have to wait before they come forward there's going to be a slight dip.
"But there's other reasons as well, such as public messages about Omicron not being that serious. It's important to stress Omicron is only less serious if you've got a level of immunity and we sadly do still have people in critical care in our county who have not been vaccinated."
NHS England has confirmed 45 Covid patients have sadly died in NGH and KGH since January 1 while eight out of 20 patients in critical care beds at Northampton General and Kettering General hospitals were being treated for Covid according to figures for Tuesday (January 18).
Health secretary Sajid Javid has hailed 'encouraging' evidence that the Omicron strain is milder than previous variants
More than one-and-a-half million jabs have been delivered in Northamptonshire but nearly one in five people have had no vaccine at all.
Mr Pallot added: "Our vaccination service is still there for first jabs, seconds and boosters. Ten percent of jabs yesterday were given to people coming forward for the very first time.
"That's really important, especially with our mobile service which is reaching outlying communities which maybe have found it harder to come forward."
A pop-up clinic is open at Sixfields, in a car park outside the Northampton Town ground, on Friday (January 21); in Towcester on Saturday and Sunday and all next week outside the Frank Bruno Foundation at Weston Favell.
Dozens more sites are open across the county for appointments, drop-ins, or both including in Northampton, Corby, Kettering, Wellingborough, Rushden, Towcester, Thrapston and Brackley.