Vaccination walk-in appointments for South Holland over 50s | Updated: 13:03, 07 April 2021 People in South Holland who are over the age of 50 and have not yet received their first Covid vaccination are being offered the chance to attend a walk-in clinic tomorrow (Thursday, April 8). The clinic will take place at the Lincolnshire Showground Large Vaccination Centre in Lincoln tomorrow, Thursday April 8, between 8am and 5pm, without a pre-booked appointment. Terry Vine, clinical and operational lead for the Lincolnshire Large Vaccination Centre explained: âWe have vaccinated thousands of over 50s across the county and are very keen to ensure anyone over 50 who is yet to have their first vaccination has the opportunity to do so, which is why we are running the walk-in appointments tomorrow.