A likely dud batch of hepatitis B vaccine has prompted a warning that anyone who received it may need to receive a booster shot.
Patients who may be at risk were vaccinated with Engerix B (batch AHBV591BB) between 9 March and 6 April.
The Medicines and Healthcare products Regulatory Agency (MHRA) is urging all concerned to contact the GP or travel clinic which administered the vaccine.
The warning has been extended to the friends and families of anyone who has been travelling overseas and who may have been in contact with the disease.
MHRA boss, Professor Kent Woods, said: "The MHRA has contacted healthcare professionals and requested them to contact all patients who have been vaccinated with this batch and invite them to be revaccinated."
The disease is usually spread parenterally or by intimate sexual contact. It is reported that in areas with high endemicity (HBsAg prevalence = 8%; eg, South East Asia and Africa), more than half of the population becomes infected at some point.
In countries with low endemicity (HBsAg prevalence = 2%; eg North America, Western Europe, Australia), most of the population do not become infected.