Hepatitis A outbreak in Portsmouth: Investigation under way
Up to 150 children and adults are to be vaccinated for Hepatitis A following an outbreak in Hampshire.
Public Health England (PHE) has confirmed seven cases of the infection within the same family in Portsmouth.
The vaccinations for children and teaching staff will take place at two schools.
The BBC understands those schools are Devonshire Infant School in Portsmouth and Fernhurst Junior School in Southsea.
PHE said the illness was "very uncommon in England" and all cases were linked through household contact.
All parents have been advised of the signs and symptoms of Hepatitis A, which is often associated with foreign travel and asked to contact their GP if they have concerns.
Dr Anand Fernandes, consultant in health protection at PHE Wessex, said: "It is an infection that can be passed from person to person, especially within households.
"We have reviewed the risk posed by this infection and have recommended the vaccination of all children and staff in specific classes as a precautionary measure.
"No other children, staff or visitors to the schools will be offered the vaccine as the risk of exposure to them is very low."
Hepatitis A can cause a range of illness from nausea and vomiting to liver inflammation, jaundice and rarely liver failure.
Dr Fernandes said good hand hygiene was important in preventing the spreading of the illness.