About 4.3 million doses of nasal H1N1, or swine flu, vaccines have been voluntarily recalled by the manufacturer because their potency was degrading over time.

The Centers for Disease Control and Prevention reported there are no safety concerns with the vaccine made by MedImmune, and anyone who received the recalled doses does not need to be revaccinated. Michigan received 114,000 doses of the vaccine, according to the Michigan Department of Community Health.

The Luce, Mackinac, Alger, and Schoolcraft (LMAS) Health Department received 700 of the recalled batches, Health Officer Nick Derusha said, and 500 had already been administered by the time the announcement was made Monday, December 22. Of the 700 recalled doses, Luce County received 129 and administered all of them, Mackinac County was sent 199 and administered 102, Schoolcraft County obtained 154 and administered 118, Alger County was given 159 and administered 117, the Sault Ste. Marie Tribe of Chippewa Indians acquired 36 and administered 35, and LMAS held 23 and administered 17 to employees.

Providers in Mackinac, Schoolcraft, and Alger counties will return any remaining doses to the manufacturer, as will the tribe, Mr. Derusha said. The Chippewa County Health Department did not receive any of the recalled vaccinations.

MedImmune's recall came a week after Sanofi Pasteur's recall of pediatric H1N1 vaccines, also owing to degrading potency.