A Brief on Different Vaccine Lot Numbers on Unit of Sale (package) and Unit of 

Use (vial/syringe) 

Date: June 21, 2018

Background 

Over the last five years, several vaccine manufacturers have implemented labeling changes related to lot 

numbers for selected vaccine products. Some of these changes, for approximately ten percent of 

publically funded vaccine products, resulted in similar but slightly different lot numbers on the unit of 

sale (UoS) which can be found on the package and the unit of use (UoU) found on the vial/syringe. 

Those vaccines with different UoU and UoS lot numbers occurred primarily among those vaccines 

which are reconstituted. This was done to denote a meaning such as the location of the manufacturers’ 

facility or the packing level. FDA regulations allow manufacturers to use different lot numbers on the 

package UoS versus the container UoU (i.e., individual syringe or vial), but do not require

manufacturers to do so. 

Challenge 

In brief, although some manufacturers use a defined pattern across UoU and UoS lot numbers, it is not 

always possible to derive the UoS lot number from the UoU lot number. Some Immunization 

Information Systems (IIS) operations require UoS lot numbers (e.g., for vaccine ordering and inventory 

management) when reporting public vaccine. However, depending on a provider’s clinical workflow and 

implemented technology solutions (e.g., recording National Drug Codes [NDCs] and lot numbers by 

scanning 2D barcodes on vaccine vials/syringes), a provider may capture and send to the IIS either the 

UoS lot number or UoU lot number. The variation in lot numbers poses a challenge to IIS and other 

health information management systems, e.g. electronic health records (EHR), with inventory modules, 

to accurately decrement the vaccine inventory from the lot number information captured at the point of 

vaccine administration. IIS and other systems have difficulty cross-walking between UoU and UoS lot 

numbers. 

Current Tools

Currently, AIRA maintains a published guidance document, Vaccine Lot Number Patterns: Unit of 

Sale/Unit of Use Guidance. This document is based upon a survey conducted by CDC to identify those 

public vaccines with different lot numbers and contains a table listing all known vaccines with different 

lot numbers and the corresponding lot number pattern for a particular vaccine. Those public vaccines 

not on this list have identical UoS and UoU lot numbers, as reported by the vaccine manufactures. The 

survey was originally done in 2014 and updated in 2016 to ensure that all applicable vaccines are 

identified. While providing a general reference on the lot numbers issue, the guidance has limitations – 

in some cases it is impossible to crosswalk between UoU and UoS lot numbers. 

Ongoing Efforts

CDC-IISSB and AIRA are both working to assess the impact on IIS of vaccines with different lot

number and to make manufacturers aware of the issue. There are several possible options to address this

matter. The first is to persuade manufacturers to return to making UoS and UoU lot numbers identical.

June 21. 2018
The second is to obtain from vaccine manufactures information on all UoS and UoU lot numbers, and to 

provide a centralized functionality for lot number mapping that IIS can utilize. This would allow the 

identification of UoS lot numbers based upon the actual UoU lot numbers, not on lot number patterns. 

A third solution, to include UoU information in the vaccine ordering system. This would be an 

expansion of both the IIS and VTrckS systems. In case of the second and third options, appropriate 

modification of IIS and VTrckS systems to accommodate crosswalk functionality would be necessary. 

A strong business case will be needed to justify such modifications. CDC and AIRA are partnering to 

continue to explore these and other potential solutions, and will be working with the IIS community to 

develop guidance as solutions are found. In the interim, we encourage IIS and immunization program 

staff to ensure providers are aware that these issues may affect the accuracy of vaccine decrementing, 

and to be prepared to correct or reconcile inventory as needed.

Updating Information 

The survey to the vaccine manufacturers went to those participating in VTrckS: GlaxoSmithKline, 

MedImmune, Merck, Novartis/GSK, Pfizer/Wyeth, Sanofi Pasture, and Seqirus. Vaccines from nonVTrckS manufacturers have not been assessed. If you become aware of any vaccine where the lot 

number differs on the UoS and the UoU (or on the UoS and the UoU lyophilized vaccine powder for the 

reconstituted vaccines), please share that information with IISinfo@cdc.org ___ and preferably include 

some images of the respective packages. 

June 21, 2018