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Background and Rationale

(draft 2001-April-11)

Click Images to Enlarge

    Accurate vaccination records are essential for various activities which maintain public confidence in and enhance the success of our immunization system: (1) monitoring the safety and side effects of vaccines, (2) determining the proportion of children protected by immunization, (3) assessing the efficacy of vaccines during epidemic situations, and (4) tracking the vaccination status of individual children by immunization registries.  

    The National Childhood Vaccine Injury Act of 1986 (U.S. public law 99-660), which established the National Vaccine Injury Compensation Program (VICP), mandates that each health care provider administering vaccines covered by the act -- principally those recommended for children -- must record in the medical record the date, manufacturer, and lot number of the vaccine (Public Health Service Act, Title 42, Chapter 6A, Subchapter XIX, Part 2, subpart c).

ERRONEOUS VACCINATION RECORDS.    The accurate transfer of such vaccine identifying information from vials to medical records and onwards into immunization registries is becoming increasingly problematic as new vaccine products with increasing numbers of antigens in combination vaccines enter the market.  One tetravalent vaccine, DTPa-HIB, has 20 words in its official generic name.  Pentavalent and hexavalent products with even longer names are being developed.

    The task of manually transcribing vaccine identity, manufacturer name, and lot number is a burden on busy health-care providers with competing responsibilities and limited time.  It is a challenge to decipher the wide variety of hastily scribbled notations often used to identify vaccines.  Omitted or ambiguous data or erroneous transcriptions inevitably occur.

    One study by Wilson and Pennisi (Pediatrics 1994;94:902-906) evaluated the accuracy of computerized immunizations records transcribed from handwritten records of 2,098 children vaccinated at the UCLA Children's Health Center during a 12 month period. The overall transcription error rate was at least 10.2%. Moreover, it was found that 38.4% of the children who were determined from the records to be "underimmunized" had previously received undocumented immunizations from other providers. 

MISSING LOT NUMBERS.    The Vaccine Safety and Development Branch (VSDB) of the National Immunization Program (NIP) of CDC oversees two major, national surveillance systems for vaccine safety.  One is the Vaccine Adverse Events Reporting System (VAERS) -- a passive-surveillance system run jointly with the FDA.  Analyses of VAERS data have found substantial rates of missing or erroneous data in the provision of lot numbers and other identifying information on adverse event report forms.  The proportion of VAERS reporting forms with missing lot numbers has increased steadily, from about 12 percent in 1993 to about 20 percent in 1997.  Presumably, this reflects missing information in the medical records upon which the reports were based.   vaersmissing_small.JPG (2244 bytes)
NONEXISTENT LOT NUMBERS.    Even when the lot number is provided, there is an increasing trend for it to be inaccurate.  The proportion of VAERS database records with "suspect" lot numbers increased steadily from a low of about 9 percent in 1992 to a high of about 14 percent in 1997. 

    Since actual vaccine lot numbers in circulation are proprietary information not available to CDC, "inaccurate" numbers were defined as those received in fewer than 5 reports from among the approximately 10,000 reports received each year.  (This may artifactually increase slightly the number of reports classified with inaccurate numbers for new lots that recently entered the market before the cutoff date of each time period.) 

vaersinaccurate_small.JPG (2244 bytes)
TRANSCRIPTION ERRORS.    Another way to assess inaccuracies in lot number reporting is by comparing rarely reported lot numbers to common ones.  The other major surveillance system maintained by VSDB is the Vaccine Safety Datalink (VSD) project, a prospective cohort study of four collaborating health maintenance organizations (HMOs).  These HMOs maintain computerized records of immunizations and medical events on their member subscribers, constituting 2 percent of the U.S. population. 

    The listing in the illustration at the right (click to enlarge) represents the first 13 lot numbers output numerically from the database for a specific DT vaccine.  The lot number recorded most frequently (the mode), 0J21027, was accompanied by many similar ones with much rarer frequency, suggesting these numbers represent reading or transcription errors.  Among all 1585 immunizations with this DT vaccine, there were 13 lot numbers reported for more than 10 vaccinations each (n=1422), while 91 numbers were reported with 10 or fewer vaccinations each (n=163).  The latter 10 percent are presumed erroneous.

    In another analysis not shown here, Wyeth-Lederle furnished lot numbers for all their DTP vaccine in circulation; 19 percent of lot numbers recorded in the VSD database for this vaccine did not exist.

vsdlots_small.JPG (2045 bytes)
UNIDENTIFIED PACKAGE NUMBERS.     It is easy to see how transcription errors can occur if one examines vaccine packaging.  This 10-dose container for OPV illustrates a source of potential error in lot number recording -- the presence of multiple numbers, none of which are identified as "lot" or "control" or whatever.  The underside of the package contains non-inked embossed numbers "0744C 12" near one edge and "MAR 97 434-990" near the opposite edge.  The expiration date is obvious, although hard to read unless the package is turned to reflect the light exactly right.  But it is not obvious which is the lot number.  dispettepackage_small.JPG (1693 bytes)
NUMBER VARIATION BETWEEN CONTAINERS.    Even smaller numbers, again without ink, are embossed on the individual plastic dispettes® containing single doses from the package above.  After clicking to enlarge the photograph at right, click here to learn the actual lot number on this dispette.  Interestingly, the final 5th digit does not appear on the secondary container, and the 5th digit on other dispettes in the same 10-dose container had differing final numbers (1,2,3, and 6), indicating the 5th digit is not part of the lot no.  This disparity between lot numbers printed on associated primary and secondary containers may also cause confusion in safety monitoring systems. stampcomparison_small.JPG (1828 bytes)
NON-INKED EMBOSSING.    Even on cardboard packaging, some lot numbers are embossed without ink, which may be difficult to read correctly under certain lighting conditions.  mmrlot_small.JPG (2011 bytes)
END-USER ASSEMBLED COMBINATIONS.    Confusion can also arise for vaccines which are combined from separate component vaccines just before administration to the patient, such as this DTPw-HIB.  The larger box (top photo) contains inner boxes with the two vaccines.  The health worker mixes the DTPw vaccine in the smallest box with the HIB vaccine in the middle-sized box (second photo). Notice three different lot numbers appearing on each box (fourth photo).  If either of the bottom two lot numbers are recorded, rather than the "pick number" representing the entire combination, there may be uncertainty in determining exactly what vaccination the child received.  hibexteriorbox_small.JPG (1716 bytes)hib3boxdisplay_small.JPG (1702 bytes)hib2vialswithlots_small.JPG (1904 bytes)hib3boxlots_small.JPG (1783 bytes)

IMMUNIZATION REGISTRIES.    Immunization registries have an important role in improving the efficiency and impact of the immunization system.  Registries are usually located within or affiliated with state and local health departments, with financial and technical assistance from public health agencies and non-governmental organizations.  

    Registries keep track of the specific vaccinations received by individual children, while maintaining appropriate confidentiality.  Their two main purposes are (1) to provide proper follow-up reminders to parents when the next doses are due, and (2) to furnish accurate and timely information to authorized health care workers about the prior vaccinations received by new patients transferring into their care.  Such information can help avoid unnecessary extraimmunization.  Future roles may include furnishing parents with documentation of vaccinations received from scattered providers to satisfy school entry requirements, reporting and monitoring vaccine adverse events, and assessing immunization coverage.  

    Registries rely on the voluntary cooperation of vaccination providers in furnishing the necessary information.  Thus, improving the convenience of recording and transmitting such information may improve the rates of participation of providers in the system.

MEDICAL ERRORS.    There is increasing concern over the frequency of medical errors occurring in health care.  Mistakes may include administering an incorrect product, using an incorrect dosage, delivering into an incorrect tissue compartment, or failing to realize the presence of a contraindicated component.  Key information to minimize this risk is now provided on vaccine cartons in a variety of formats and layouts which differ from manufacturer to manufacturer, and even from product to product within a manufacturer's line.  Standardizing the layout and format of such information might assist nurses and physicians in more readily finding the information they need. 
VISI GOALS.    To address the various problems and needs cited above, the principal goal of the Vaccine Identification Standards Initiative (VISI) is to develop voluntary guidelines for improved packaging and labeling of vaccines in order to increase the accuracy, efficiency, safety, and convenience of the vaccination process, especially the transfer of essential vaccine identifying information from the vaccine vial into the medical record and onwards into immunization registries. 

     VISI is a voluntary, cooperative effort among relevant and interested individuals and organizations which comprise the vaccine and immunization system. 

     VISI has focused on developing application guidelines and prototypes which fall into six major related components:

  1. Peel-off stickers containing all essential information in English and barcoding affixed by manufacturers on their vaccine vials and prefilled syringes
  2. Redundant full barcoding of essential information on outer cardboard packaging
  3. Uniform vaccine administration record form to receive peel-off stickers
  4. National Drug Code vaccine database on the web to identify vaccines from their NDC and vice versa
  5. Vaccine Facts sidebar on outer cardboard packaging to standardize the format and location of key information needed by immunization providers
  6. Standardized abbreviations for vaccine types and vaccine manufacturers and distributors


TriHIBit™ generic name  =  "Haemophilus b Conjugate Vaccine (Tetanus Toxoid Conjugate) -- ActHIB®  Reconstituted with Diphtheria and Tetanus Toxoids and Acellular Pertussis Vaccine Adsorbed -- Tripedia®"   {Return to text where TriHIBit™ generic name cited }

Embossing on OPV dispette  =  744C3   {Return to text where OPV lot number discussed

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This page last modified on March 17, 2003


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