Study Methods and Data Limitations


From September 2004 to June 2005, statutes, regulations, opinions, and other legal requirements in the 50 United States and the District of Columbia (DC) were collected using Lexis-Nexis and public web-based databases. Requirements for hospitals, ambulatory care facilities, individual providers' practices, correctional facilities, and facilities for the developmentally disabled - but not for long-term care facilities - were collected. Because many states have different definitions for the same type of facility, legal analysts developed a set of project-specific definitions to standardize data collection (see Definitions). Three categories of laws are included in this database: assessment, administration, and hepatitis B laws.

Vaccine-specific laws as well as more general laws requiring persons to be up-to-date with all age-appropriate vaccinations were collected. Laws were grouped by population and facility type, vaccine type, and - for administration laws - whether the law was an offer or ensure law.

Questions regarding interpretation of ambiguous legal language were resolved through telephone and e-mail contact with the legal counsel designated by each state as its primary public health attorney. In addition, legal counsel from every state were given the opportunity to comment on the accuracy, completeness, and interpretation of findings of the conclusion of the review.

The summary data reported in this database will be updated periodically as NCIRD becomes aware of new laws or regulations, or modifications to existing laws or regulations. Copies of state laws and administrative rules or regulations were also collected to serve as a resource for states considering legislation.

 Top of Page

Periodic Updates

Information on assessment and administration laws is periodically updated to reflect changes in state immunization requirements. Weekly summaries of a Lexis-Nexis search for bills containing keywords “vaccin!” or “immuniz!” are reviewed by NCIRD staff, and bills that have become law are evaluated for inclusion in the database. For hepatitis B screening and reporting requirements, weekly summaries of a Lexis-Nexis search for bills or revised regulations containing keywords “hepatitis” or “HBsAg” or “pregnan!” and “disease” are reviewed.

Judgments on whether a new law meets inclusion criteria and what type of requirement such a law sets forth (i.e., assessment, offer, ensure) are not reviewed by state legal counsel. As noted below, interpretations made by our legal analysts may not be consistent with the way legal requirements are interpreted in each state. The database is updated periodically to reflect current state requirements, but no less often than every 6 months.

 Top of Page

Limitations & Data Notes

Statutes and regulations pertaining to immunization are located under the authority of different departments and agencies in each state; therefore, our database may inadvertently omit some laws that should be included. Although state counsel were given the opportunity to review results, not all of them responded; therefore, interpretations made by our legal analysts may not be consistent with the way legal requirements are interpreted in each state, The laws of each state are constantly changing: our results are up-to-date as of November 2014.

Our results reflect vaccination requirements and exemptions as they are written into state law, but this review did not measure how or if these laws are enforced. We included prophylactic (pre-exposure) vaccination only, and did not include laws pertaining to vaccine assessment or administration following suspected exposure to any disease. Each entry in the database includes the language of the statute or regulation establishing the requirement noted, but this is not necessarily the verbatim text of the law in question. Readers who wish to see the exact language of the law should always consult the source of law cited.

 Top of Page

(For detailed methods and results, please see Lindley MC, Horlick GA, Shefer AM, Shaw FE, Gorji M. Assessing state immunization requirements for healthcare workers and patients. Am J Prev Med 2007; 32(6):459-465.)

Disclaimer: The purpose of this database is to provide researchers, policymakers, and state and local public health practitioners with descriptive information concerning immunization-related state laws. No part of this legal analysis involves providing legal advice or answering specific questions of law on behalf of any person or organization.


Page last reviewed: November 19, 2014