U.S. health officials issued a warning Tuesday about counterfeit Botox injections that have sickened 22 people.

Half of the individuals have ended up in the hospital, according to the Centers for Disease Control and Prevention. The agency issued an alert to doctors on Tuesday.

The cases started in early November and have been reported in 11 states. The CDC said the shots were administered by unlicensed or untrained individuals or in settings like homes or spas. Most of the people said they got injections of botulinum toxin for cosmetic reasons.

Six people were treated for suspected botulism, health officials said. When it gets into the bloodstream, botulinum toxin can cause botulism, a deadly disease that starts with double or blurred vision, drooping eyelids, slurred speech, difficulty swallowing and difficulty breathing.