A Northern California health clinic gave 14 children the wrong dose when administering pediatric COVID-19 vaccines over the weekend.

Sutter Health said in a statement that 14 of the vaccinations given at its pediatric clinic in Antioch had “an incorrect amount” of diluent, which is used to dilute the concentrated form of the vaccine, KGO-TV reported. The statement did not specify if the doses were too much or too little.

“As soon as we learned this we contacted parents,” Dr. Jimmy Chu, the chair of Sutter Health’s COVID-19 task force, said in the statement. “And we immediately reviewed our processes to help make sure this doesn’t happen again.”

Side Effects from Higher Doses

Denise Iserloth told the station that the clinic notified her about 10 hours after her children, ages 8 and 11, had received 20 micrograms of vaccine instead of the recommended 10. Both children were home sick Monday with bad stomach aches, she said.

“We would have assumed that there was more in place to prevent this from happening, but obviously at this place there wasn’t,” said her husband, Shawn Iserloth.

According to the U.S. Centers for Disease Control and Prevention, patients who receive a vaccine with an incorrect dose may experience more arm soreness, fatigue, headache, or a fever.

Dr. Peter Chin-Hong, an infectious disease expert at the University of California, San Francisco, told KGO-TV that children were given higher vaccine doses in clinical trials and showed no ill effects.