This column was prepared by the Institute for Safe Medication Practices (ISMP), an ECRI affiliate.

Multiple mix-ups between the pediatric formulation (ages five through 11 years; orange cap and label border) and the formulation for individuals 12 years old or older of the Pfizer-BioNTech coronavirus disease 2019 (COVID-19) Vaccine have been reported to the Institute for Safe Medication Practices (ISMP) since Food and Drug Administration (FDA) authorized emergency use of the vaccine for children ages five through 11 on October 29, 2021. While details about the contributing factors were not provided in many cases, below is a highlight of what we have learned from the reports.

Five reports described cases in which 12-year-old children received doses (underdoses) that were appropriate for five- to 11-year-old children (10 mcg/0.2 mL rather than 30 mcg/0.3 mL). In three of these cases, those administering the vaccine were unaware of the proper dose for 12-year-old children. In addition, several reports indicated that children five to 11 years old received doses intended for individuals 12 years and older. In one case, those administering the vaccine had not yet been made aware that a pediatric formulation existed, and that the dose was different for individuals 12 years and older. So, the children were given 30 mcg/3 mL of the Pfizer-BioNTech COVID-19 Vaccine in error. High patient volume was mentioned as a factor in other reports.

Finally, the 30 mcg/0.3 mL Pfizer-BioNTech COVID-19 Vaccine (intended for individuals 12 years and older) was used to vaccinate some children ages five to 11 years as it was thought to be acceptable if only 10 mcg was given, either as 0.1 mL of the 30 mcg/0.3 mL vaccine (10 mcg) or by diluting the 10 mcg dose in a syringe to 0.2 mL. In one event reported via the news media, 112 children aged five to 11 years received their vaccine in this manner. Neither method would be correct though, since the pediatric vaccine is specifically formulated to be more diluted to ensure accurate measurement. Withdrawing 0.1 mL in a 1 mL syringe will result in an inaccurate volume, as it is recommended that no less than 20% of the nominal syringe capacity is measured to limit instrumental error. Also, if a needle different from the one used for drawing up the vaccine is used for administration, some of a 0.1 mL dose would likely be lost to any dead space. Or if a 0.1 mL dose is drawn up and the same needle and syringe are used to draw up a 0.9% sodium chloride diluent, then the vaccine in any dead space of the needle and syringe hub will be initially drawn into the syringe as it is pulled back to withdraw the diluent. Depending on how evenly the vaccine is distributed in the syringe, this could result in too much or too little vaccine reaching the patient upon injection.

Segregate and store these vaccines in refrigerators and freezers that are organized and properly labeled. Store the adult (12 years and older) and pediatric COVID-19 vaccines apart from one another, such as in separate labeled plastic bins. During the production and/or verification phase of the dispensing process, use barcode scanning whenever possible to verify that the correct product has been retrieved. Clearly label all individual syringes containing vaccines. To facilitate proper labeling, print labels for each patient or provide vaccine preparers with strips of preprinted labels that differentiate adult and pediatric doses. Ideally, prior to administration, barcode scanning should again confirm the correct vaccine. Also, only bring the intended and labeled vaccine syringe(s) for one patient into the vaccination area at a time. Involve the parent or patient in verifying the vaccine by reading the label to confirm the correct vaccine.