In Northamptonshire, that could mean jabs for 250,000 people in just three weeks.
From this week anyone aged 18 or over can attend any clinic offering booster doses as long as their second dose was at least three months ago.
The sites are not open all day, every day and certain jabs — first, second or boosters — may only be available at certain times on certain days, so it's important to check at which clinics you can be seen without an appointment.
Click HERE for up-to-date details on walk-in clinics at these locations around the county:
■ Corby — Mr Pickford's, Spencer Court; Oakley Pharmacy, Charter Court; The Raven Hotel, Rockingham Road.
■ Northampton — Ramgarhia Sikh Temple, Cromwell Street; Regent Pharmacy, Regent Street; St Michael and All Angels' Church, Perry Street; Whitefields Surgery, Hunsbury Hill Road.
■ Rushden — Harborough Field Surgery, Newton Road.
■ Wellingborough — Pravasi Mandal Centre, Elsden Road.
■ Brackley — Methodist Church, High Street.
■ Towcester — Towcestrians Sports Club; Greens Norton Community Centre.
Over 30s can already book a booster online, from two months after their second dose. From Wednesday this will be extended to over 18s.
To book an appointment for a booster vaccine dose, visit the NHS website HERE or call 119. Bookings are now open to all those aged 30 and above and will extend to everyone aged 18 and over on Wednesday December 15.
Many areas reported queues at drop-in clinics around the country on Monday (December 13) following the Prime Minster's address urging the nation to get jabbed to avoid a surge of Omicron variant cases, which could overhwelm the NHS.
Evidence so far suggests that Omicron may be more infectious than previous variants and that existing vaccines may be less effective at stopping it
However, early studies suggest that an extra dose of vaccine can prevent around 75 percent of people getting any Covid symptoms.