CHICAGO (AP) -- The Illinois Public Health Department said Friday it would make the smallpox vaccine available for anyone who has been exposed to monkeypox.

The federal Centers for Disease Control and Prevention on June 11 recommended the vaccine for treatment and prevention of the disease, which officials believe was spread by infected prairie dogs from a pet distributor in suburban Chicago.

Illinois Public Health Director Eric Whitaker said the state waited to analyze the risks of the vaccine. Wisconsin has already offered the smallpox vaccine to people exposed to monkeypox, but officials said there were few takers.

According to the CDC, the vaccine causes serious side effects in about one out of every 1,000 recipients and is fatal in one out of every million cases.

"Our concern is the smallpox vaccine is worse than the disease," Whitaker said. "We're not recommending this, we're saying it's available."

State epidemiologist Mark Dworkin said the state was investigating 17 possible cases of monkeypox, including five that had been confirmed. Nationwide, there are at least 87 possible cases of the disease, with 20 cases being confirmed.

Health officials estimate about three dozen people -- health care workers, investigators, patients and their family members -- qualify for the vaccination.

Monkeypox, a west African disease not previously seen in the Western Hemisphere, is related to smallpox but is not as lethal. It causes rashes, chills and fever. No one has died in the United States from the disease.

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