Welcome to winter, Brighton!
Unfortunately, winter means colds, and while we’d love to offer some helpful tips on how to avoid a cold, the best we can do (if you don’t want to wear a face mask all day) is advise you to wash your hands after touching communal spaces like public transport straps or lift buttons, don’t share cutlery or cups, and generally try to not breathe other people’s infected exhaled air!
Sorry we can’t offer more - vitamins and supplements simply have almost zero proven effect on cold prevention (but a healthy diet is never a bad option!).
Stay healthy!