Burgers should be thoroughly cooked
Food Standards Agency (England) issued guidelines for restaurants that wish to serve rare burgers. Scottish Craft Butchers agree with Food Standards Scotland, however, when they announced it will not be revising its guidelines - so chefs in Scotland must still cook their burgers all the way through, ensuring no pink bits and that juices run clear. This helps safeguard the consumer.
A Burger is not a Steak
While rare steaks are safe to eat (food borne illness bacteria occurs only on the outside surfaces of beef muscle) rare burgers are potentially highly risky as the outside of the meat is minced through with the internal muscle, rendering the whole contaminated.
Whether eating out or eating in always ensure your burger is cooked through to minimise the risk of contracting a potentially fatal food borne illness.