More on preparation errors with Pfizer-BioNTech COVID-19 vaccine
The ISMP National Vaccine Errors Reporting Program (VERP) continues to receive reports of errors occurring during preparation of the Pfizer-BioNTech coronavirus disease 2019 (COVID-19) vaccine. Unlike the Moderna vaccine, the Pfizer-BioNTech vaccine must be diluted prior to use. After thawing, the multiple-dose vial contains 0.45 mL of concentrated vaccine that requires further dilution using 1.8 mL of preservative-free 0.9% sodium chloride injection. After dilution, each vial contains 6 (or even 7) doses when using low dead-volume syringes/needles to extract the 0.3 mL (30 mcg) dose. In our January 14, 2021 issue, we described instances where the Pfizer-BioNTech COVID-19 vaccine had been improperly diluted with too little diluent, or no diluent at all. More recently, though, reports have reached us where air has been used accidentally as the “diluent” for the Pfizer-BioNTech COVID-19 vaccine.
These errors have happened in mass vaccination clinics where more than one person is often involved with the vaccine preparation and administration process. In these clinics, practitioners sometimes open the syringe packages and draw the syringe plunger back to the appropriate amount of diluent (1.8 mL) or vaccine (0.3 mL) that will need to be withdrawn from the vial, leaving only air in the syringe. Injecting air into the vial in the same amount as the volume being removed from the vial equalizes the pressure and allows the desired amount of diluent or vaccine to be withdrawn.
In one case, pharmacy staff were diluting the Pfizer-BioNTech vaccine vials, and nurses were drawing up the doses. In the process of labeling what was thought to be vaccine, it was noticed that several of the syringes contained only air and no vaccine. It was discovered that one of the nurses was unpackaging 1 mL syringes, pulling back 0.3 mL of air as described above, then putting the syringes back down with the caps on. She was later going to draw up vaccine doses with these syringes that she previously filled with air. However, others nearby thought these syringes were already filled with 0.3 mL doses of the vaccine, so they moved them to the labeling section of the table. Fortunately, the pharmacist noticed empty syringes where the vaccine was supposed to be and corrected the problem. This was experienced twice at the same facility on separate days.
At another public health immunization clinic, a healthcare worker drew up 1.8 mL of “diluent” to inject into a Pfizer-BioNTech vaccine vial. The vaccine was “mixed,” and the first dose of 0.3 mL was drawn into a syringe and given. However, when the second dose was withdrawn from the vial, there was not enough vaccine remaining in the vial to prepare a 0.3 mL dose. It was determined that 1.8 mL of air had been injected into the vial, but no actual diluent. The patient who received the first dose from the vial received undiluted vaccine. Investigation of the event revealed that unpackaged syringes drawn up with air for use with the diluent vials had been used as if they contained the diluent.
Whenever possible, a pharmacy should prepare and label vaccine doses for mass vaccination programs ahead of time after verification of the number of confirmed appointments or anticipated patients. Do not pre-open syringe packages to draw up air in advance. This risky practice is error-prone and may contribute to possible contamination of the vaccine. Instead, be sure practitioners completely prepare one vial at a time.