LANSING, Mich. -- Sanofi-Aventis SA, the maker of the H1N1 vaccine, is recalling about 800,000 doses of the pediatric H1N1 vaccine because tests found the potency was too weak to effectively protect against the virus.

Michigan has received about 17,200 doses of the vaccine, which is for children ages 6 months to 3 years old.

Health departments, clinics or private doctors offices in 38 Michigan counties received the recalled doses.

The counties include Allegan, Alpena, Bay, Genesee, Ingham, Isabella, Lapeer, Livingston, Saginaw and St. Clair.

While the antigen content of these doses is now below the specification limit for the product, the Centers for Disease Control and Prevention and the Federal Drug Administration are in agreement that the small decrease in potency is unlikely to result in a clinically significant reduction in immune response among persons who have received the vaccine.

For this reason, there is no need to revaccinate persons who have received vaccine from these lots.

Providers are being asked to return any vaccine that remains unused to the manufacturer from the specified lots. The CDC also notes the following:

• There are no safety concerns with these recalled lots of 2009 H1N1 vaccine. All doses successfully passed pre-release testing for purity, potency and safety.
• Only specified batches of the 2009 H1N1 pediatric vaccine for children 6 months to 3 years old in pre-filled syringes are affected.
• There is no need to readminister a dose to those who received vaccine from these batches.
• Parents of children who received vaccine from the recalled batch do not need to take any action, other than to complete the two-dose immunization series if not already completed.
• Children should receive both doses of 2009 H1N1 vaccine from the same type of vaccine (i.e., both doses as inactivated, injectable; or both doses as live, attenuated, nasal spray vaccine).
• All vaccines are routinely tested for purity, potency and safety prior to release.

Michigan residents can help stop the spread of the virus by washing hands thoroughly and often; covering mouths when sneezing or coughing; and staying home from work or school if sick.

For more information on vaccine availability, check the MDCH Web site at www.michigan.gov/MDCH, or call 866-561-2500.