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This report shows the percent of Vermont children, ages 19-35 months, who have received the full series of recommended immunizations (4:3:1:4:3:1:4) by county and Agency of Human Services (AHS) District. The Vermont Department of Health’s Immunization Program works with families, providers, and community partners to make sure children and adults are protected against vaccine-preventable disease. The Program maintains Vermont’s Immunization Registry, which is a confidential, population-based, computerized database that contains a record of immunization doses administered by participating providers to persons residing within a given geopolitical area. At the population level, a registry provides aggregate data on vaccinations for use in surveillance and program operations, and in guiding public health action with the goals of improving vaccination rates and reducing vaccine-preventable disease. Vaccines, especially in early childhood, are a way to reduce epidemics of many preventable diseases that negatively impact the health and well-being of populations. 

The Vermont Immunization Registry (IMR) is a confidential, computerized system for maintaining immunization records, designed, developed, and is operated by the Vermont Department of Health. The IMR saves money by ensuring that patients get only the vaccines that they need. It also improves office efficiency by reducing the time needed to gather and review immunization records. And in the case of disease outbreaks or public health emergencies, medical providers can use the IMR to identify individuals at risk (Vermont Department of Health, n.d.).

The IMR was first made available to providers in July 2004. Most medical provider sites in Vermont send immunization data directly from their Electronic Health Records to the IMR via HL7 message – this information loads within 2 business days. HL 7 is a set of international standards for transfer of clinical and administrative data between software applications used by various healthcare providers. 93% of Vermont practices serving children are actively using the registry, but a few practices are still struggling to fill in historical records for older patients – so some records can be incomplete. All Vermont hospitals except the Veterans Administration report immunizations. The five largest health insurers and an increasing number of pharmacies and nursing homes report immunizations as well, which helps to fill in records (Vermont Department of Health, 2016).

The results in this report represent the percentage of children, ages 19 to 35 months, who have received the full recommended series of vaccines.  This is often represented as vaccine series (4:3:1:4:3:1:4), which is seven different vaccines with unique doses:

  • 4+ DTaP: 4 or more doses of diphtheria, tetanus and pertussis vaccine;
  • 3+ Polio: 3 or more doses of poliovirus vaccine;
  • 1+ MMR: 1 or more dose of a measles, mumps, rubella vaccine
  • 4+ Hib: 4 or more doses of Haemophilus inu001fuenzae type b vaccine
  • 3+ HepB: 3 or more doses of hepatitis B vaccine;
  • 1+ Var: 1 or more doses of varicella vaccine;
  • 4+ PCV: 4 or more doses of pneumococcal conjugate vaccine.

The information below about data quality, timeliness, and accuracy was obtained from VDH’s Vermont Immunization Registry Data Brief (April, 2016).


  1. Data Quality
  2. Timeliness
  3. Timeliness
  4. Accuracy

I. Data Quality

How ‘good’ is the data in the IMR? It’s an important question. Practices want to know if the vaccine coverage rates they are measured by are accurate, and the health information they rely on is correct. Since the information in the IMR comes from different sources including hospitals, provider offices, the Special Supplemental Nutrition Program for Women, Infants, and Children WIC) clinics, and health insurers, it is important to measure data quality. Immunizations are added to the IMR in a day or two directly from provider Electronic Health Records, through monthly imports from health insurers and pharmacies, and through direct record entry by immunization providers. All senders are assessed for quality before information is accepted, and monitored for quality assurance on an ongoing basis.

II. Timeliness

The IMR currently receives immunization information via HL7 messaging. This has allowed the IMR to have a complete immunization record for a patient much earlier than when batch importing from the provider or insurer was the primary data source. The charts below shows how providers enrolled in the state’s Vaccines for Children (VFC) program relayed information to the IMR, as compared to 2012 before HL7 messaging began.


Number of Days from Immunization Administration to Receipt in the IMR for Children 19- to 35-Months Old*

*Data Source: Vermont Immunization Registry

III. Completeness

The IMR contains information on all Vermont births, as well as information from other states for children residing in Vermont who were born elsewhere. Furthermore, the vast majority of practices submit data to the IMR, leading to a high level of immunization record completion for children living in Vermont. The National Immunization Survey (NIS), administered by the Centers for Disease Control and Prevention (CDC), is the standard national survey of immunization rates for states. The chart below shows that the vaccine coverage data in the IMR is consistently within the confidence intervals of the NIS results for the complete infant immunization schedule.


Full Series Vaccination Rates for 19-35 Month Olds Comparison of the Vermont Immunization Registry and the National Immunization Survey*

*Data Sources: Vermont Immunization Registry, National Immunization Survey


Historically, one challenge to immunization record completeness has been that some Vermonters get health care out of state. Thanks to a recent change in the law, the IMR is now able to establish record exchanges with other states for the purpose of getting complete immunization histories for Vermont residents. Currently, the IMR routinely imports data for Vermonters who are immunized at Dartmouth Hitchcock Medical Center and its associated practices in New Hampshire.

IV. Accuracy

The accuracy of data the IMR receives is of crucial importance. VDH strives to receive data on the exact immunization that was administered. This requires proper coding in the electronic health record. Many vaccines have codes for ‘unspecified’ types that allow the immunization information to be sent without fully identifying the type of vaccine. This is something the Department has sought to avoid. Since 2012 the number of immunizations sent with the unspecified code has dropped by 55%, allowing for improved forecasting and use of the IMR. For example, the rotavirus vaccine is made by two manufacturers. One brand of vaccine requires two doses and the other three doses. Without specification on which brand was received, it is difficult to determine if the child is up-to-date or needs additional doses.

It is also important to have an accurate picture of which patients are associated with a practice. Over time, it can be difficult to track where a patient is living and where they are receiving care. The IMR has a feature that allows a practice to identify a patient as ‘Moved or Gone Elsewhere’, so they will not be counted in reports for that practice. Active management of patients helps practices optimize their vaccine coverage.

The percentage of 19 to 35 months old who received the full series of recommended vaccinations (4:3:1:4:3:1:4) was calculated using the following formula:

([Count of 19 to 35 Month Olds Who Received the 4:3:1:4:3:1:4 Vaccination Series for the Geography and Year] / [Population Count for 19 to 35 Month Olds for the Geography and Year]) * 100

The count of 19 to 35 month olds who received the 4:3:1:4:3:1:4 vaccination series for each geography and year was extracted from Vermont’s IMR.  The population count for 19 to 35 month olds for each geography and year was obtained by VDH from the CDC’s National Center for Health Statistics.

As is the case with any large database, Vermont’s IMR has its limitations. It can be very difficult to keep up with the residences of all individuals, resulting in a larger population base in the registry than actually live in the state of Vermont. As a result, the denominator can be too large. Vaccine Coverage Reports for 2-3 year olds, for instance, may include some records for patients who have moved out of state, but reports for teens are likely to include many more (Vermont Department of Health, 2016).

The percentage of Vermont practices not utilizing the registry is small (about 20%). The IMR receives immunization records for Vermont residents who seek care in New Hampshire at Dartmouth Hitchcock Medical Center.  For the years 2013 and 2014, there may be incomplete records for those individuals who may otherwise seek care out of state. 93% of Vermont practices serving children are actively using the registry, but a few practices are still struggling to fill in historical records for older patients – so some records can be incomplete. Thus, the results may give an incomplete picture of vaccine coverage (Vermont Department of Health, 2016).