I usually get my flu jabs at a local out-of-town NHS building, set back from the road and hidden behind trees, with a surprisingly large parking area out of sight behind it and a small visitors parking area in front.
It was first activated, AFAIK, in the Pig Flu epidemic, but never had a sign outside it until then. It now has a dispensing pharmacy (not a chemists shop). The open-to-the-public area is a tiny fraction of the building, which appears to have just about no-one it (hardly any staff cars) and no windows.
I sometimes wonder if the parking area round the back was designed for refrigerated trailers.