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URBANDALE, IOWA — More than 100 children were given a double-dose of a COVID-19 vaccine accidentally at a MercyOne clinic over the weekend, the hospital says. It happened a clinic held on Saturday in Urbandale. MercyOne says 107 children under the age of 12 were given 20 microgram doses of the vaccine instead of the intended 10 microgram dose.

They say side effects from the double-dosage would include more “pronounced post-vaccine responses” – meaning a sore arm, headache, fatigue or fever could last longer than normal. No serious side effects or health issues are a concern. All children who were given the incorrect dose have been contacted by MercyOne.

MercyOne released this statement on the misdosages:

“MercyOne has become aware that children under the age of 12 received an incorrect dosage of the Pfizer COVID-19 vaccine at a mass vaccination clinic held on Saturday, Nov. 20. The prescribed dose is 10 micrograms for children under 12 years old, and children received 20 micrograms. An adult vaccine dose is 30 micrograms.

Representatives from MercyOne are proactively contacting all parents, and MercyOne pediatricians are available to answer any questions parents may have. Anticipated side effects from the mis-dosage may include more pronounced post-vaccine responses such as a sore arm, mild fever, headache and fatigue.

All adults and adolescents ages 12 and older who attended the vaccination clinic were given the appropriate dosage. MercyOne is implementing procedures to ensure a similar incident does not happen again. MercyOne strongly believes in the safety and efficacy of all COVID-19 vaccines available to eligible age groups. Vaccination continues to be the most effective way to protect yourself from the COVID-19 virus and its variants.”