About 80 people might have been exposed to hepatitis A - and not know it

Diners at Christchurch's Madam Woo are being urgently contacted by the Canterbury DHB after a chef working at the restaurant had the disease.

Medical Officer of Health, Dr Ramon Pink says people who bought food at the restaurant on January 15 and January 17 could be impacted.

Pink says the vaccine is free and anyone who dined there on January 15 must get vaccinated by tomorrow to avoid developing the disease.

People who went to Madame Woo on January 17 must get a jab by Friday.