A group of children who received flu shots at a Colorado clinic are now being tested for several infectious diseases including HIV, Hepatitis B and Hepatitis C after a mix-up that led vaccine syringes to be shared between patients, 9News.com reported.

It happed at the Med Peds Clinic in Fort Collins, and on April 6, the clinic sent out letters to families explaining that a medical assistant “took the pre-measured children's influenza vaccine and only gave half to each child, assuming it was the adult dosage.”

Unlike adults, kids are supposed to receive two doses of the pediatric flu vaccine. With that understanding, officials at the clinic said the assistant removed the needles from the half-full syringe – assuming it was the adult dose – and replaced it with a sterile needle, but not a new syringe.

The syringes were then placed in a box marked “second doses.”

As a result, the clinic said some of the half-used vaccines were used on children who returned for their second influenza shot.

"Apparently, somebody wasn't following policy and procedure and it puts infants in danger, so [I'm] not a big fan of them right now," Cary Bergeron, whose infant was vaccinated at Med Peds, told the news station. "She was born flawless, and now, by someone else's mistake, something bad could happen."

The clinic said the assistant has since been fired and they are taking precautions to make sure this doesn’t happen again.

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