Use of Immunization Registry During Measles Outbreak, Indiana 2011

Background:  An unvaccinated Indiana resident returned from overseas while infectious with measles in June 2011. The subsequent investigation uncovered 13 additional cases that were epidemiologically linked to the index case. The Indiana Children and Hoosiers Immunization Registry Program (CHIRP) was used to help determine the immunization status of case contacts.  

Objectives:  Rapid determination of the immune status of exposed persons is critical during a measles outbreak to identify susceptible individuals. CHIRP was utilized to assess the immunization status of all potentially exposed persons.

Methods:  ISDH investigators accessed CHIRP to assess the immunization status of all contacts. This information was used to determine if the exposed contacts needed to be vaccinated and/or isolated.

Results:  Two infectious contacts of the index case traveled by bus with 23 classmates and 4 adults to an amusement park during summer vacation; 23 (85.2%) exposed travelers had two doses of measles vaccine documented in CHIRP, which required no intervention. Immunization records for all travelers were examined within 2.5 hours, which was a significant time savings over tracking down individual records from contacts’ schools or health-care providers. In another instance, a factory employee worked for two days while infectious. Since the workers were adults, many would not have had easy access to their immunization records.  Immunization records for all 346 employees were examined in CHIRP. Forty six employees (13.3%) had at two doses of measles vaccine documented and no further testing or vaccination was necessary.

Conclusions:  Having an accessible database of immunization records decreased the time necessary to assess the immunization status of contacts; this provided useful information that helped guide interventions during the 2011 measles outbreak in Indiana.  As the number of vaccinations in the registry increases, the usefulness of the registry to vaccine preventable disease investigations will also increase.