10/04/2012 11:19 EDT | Updated 12/04/2012 05:12 EST

Sanofi recalls batches of typhoid vaccine; not as potent as should be

TORONTO - Vaccine maker Sanofi Pasteur is recalling several batches of its typhoid fever vaccine over concerns the doses may not be as potent as they should be.

The company says the batches of the vaccine, called Typhim Vi, may contain less antigen than they should.

Antigen is material that prompts the immune system to create antibodies against the bacteria or virus targeted by a vaccine.

Sanofi says there is no safety concern for people who may have been vaccinated with the substandard batches of Typhim Vi.

And the company is not recommending that people go for a booster shot earlier than they are normally scheduled to do so.

But Sanofi acknowledges the recall may lead to a typhoid vaccine shortage.

The company hasn't said how many batches of vaccine are involved in the recall. Nor have they said what caused the problem.