People who have had a particular vaccination for typhoid are being told to contact their doctor if they expect to visit areas where typhoid is common.
Manufacturer Sanofi Pasteur MSD has recalled 16 batches of its Typhim Vi vaccine after tests found that some samples are weak and may not be effective enough.
The BBC reports there is no safety problem, but anyone immunised with the vaccine since January 2011 could be affected.
A research director at the Auckland University-based Immunisation Advisory Centre says the batches involved have been used in New Zealand by GPs and travel doctors.
Helen Petousis-Harris says the vaccine is used by people intending to travel to high-risk areas, such as south Asia and south-east Asia, and by sewage workers.
Anyone who expects to be in areas where there is typhoid should contact their GP to find out if they had the affected vaccine.
Dr Petousis-Harris says it is not known how many people may be affected.
