A vaccine maker is recalling batches of typhoid fever vaccine that may not be potent enough.
Health Canada said Thursday that Sanofi Pasteur is recalling batches of the Typhim Vi vaccine.
"There is no safety concern for individuals who have received a Typhim Vi vaccine dose from a recalled batch," Health Canada said in a statement.
"The doses were identified as potentially having less antigen, the substance that stimulates the immune system to produce antibodies against the disease."
Typhim Vi vaccine is used to immunize people against S. typhi, the organism that causes typhoid fever, in those aged two or older.
The company is not recommending that people go for a booster shot earlier than normally scheduled.
"The recall may lead to a typhoid vaccine shortage," the notice said.
"The Typhim Vi recall is expected to impact not only Sanofi Pasteur's worldwide supply of its vaccine, but may also lead to a typhoid vaccine shortage within the next few weeks/months," Nancy Simpson, director of communications for Sanofi Pasteur, said in an email.
"The company is fully conscious of the public health impact that this recall may cause and is investing all possible means at its disposal to resolve this issue as quickly as possible. The situation may be different from country to country depending on the local presence of typhoid fever manufacturers and on country stock."
Canada has two other suppliers of typhoid vaccines, the regulator said.
Sanofi said it's investigation suggested the amount of antigen varied in some syringes and 20-dose vials of these batches that are being recalled: G1122-1, G1557-1, G0182-2, H0176-1