Had my 'flu jab today in the car. The arrangement at the clinic is at or near your appointment time you park in the ambulance bay (enough room for two cars parallel parked) and toot the horn once. A nurse protected facially with a full-face clear visor comes out pushing a cart with all the accoutrements aboard.
She then approaches the patient & gets their name before heading back to the cart to get the sterile swab, syringe & bandaid. A very quick jab & slap on the dressing then I'm off.
As far as the nearest vacant parking space in the clinic's carpark to wait 15 minutes in case some reaction occurs. One such reaction is sudden lowering of blood pressure. Should that happen, I was to lean on the horn & keep it tooting until the nurse & a doctor arrive.
I experienced no complications.