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Age-Related COVID-19 Vaccine Mix-Up

A November 4, 2021, SAFETY brief addressing the possibility of mix-ups between the pediatric formulation (orange cap and label border) and the formulation for individuals 12 years of age or older of the Pfizer-BioNTech coronavirus disease 2019 (COVID-19) vaccines has proven to be accurate, with multiple mix-ups reported to ISMP in just the past 2 weeks. Five reports described cases of underdosing in which 12-year-old children received doses appropriate for 5- 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. Two cases were unexplained.

Conversely, there have been several reports of 5- to 11-year-old children who have received a higher dose intended for individuals 12 years and older. In one case, although a specific parental consent form was used for the 5- to 11-year-old age group, 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/0.3 mL of the Pfizer-BioNTech COVID-19 vaccine in error.

Another mix-up occurred due to a misunderstanding regarding the meaning of the letter P, intended to stand for “Pfizer” but mistaken as “pediatric,” that was used on the syringe labels of COMIRNATY, the brand name for the US Food and Drug Administration (FDA)-approved Pfizer-BioNTech COVID-19 vaccine for ages 16 and older (doses for ages 12 to 15 years are approved under an Emergency Use Authorization [EUA]). The P was used to differentiate the Pfizer vaccine from the Moderna vaccine. The reasons for the remaining mix-ups were either not provided or attributed to high patient volumes.

There were also some children ages 5 to 11 years for which the 30 mcg/0.3 mL Pfizer-BioNTech vaccine (intended for individuals 12 years and older) was used but 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 ages 5 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 the 0.1 mL dose would likely be lost to dead space in the needle. 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 initially in any dead space of the needle and syringe hub would be 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.

ISMP also received a report in which a hospital requested numerous physician offices to schedule 5- to 11-year-old children for the Pfizer-BioNTech 30 mcg/0.3 mL vaccine because the vials were expiring soon, with the misunderstanding that 10 mcg doses could be prepared from that formulation for the younger children. However, ISMP was unable to confirm if any doses were actually administered in this manner. Additionally, ISMP is following up on two error reports received this week, one involving 14 children (ages 5 to 11), who received vaccine meant for individuals 12 years and older, and the other involving 22 children (ages 5 to 11) who also received vaccine meant for the older age group.

For additional information and recommended error-prevention strategies, please see our November 4, 2021, SAFETY brief available here.