Context

Vaccinations provide people the ability to develop immunity to particular diseases. When the majority of a population is vaccinated, “herd immunity” protects those who have not been vaccinated by blocking the spread of these diseases. A medical research paper published by The Lancet in 1998 suggested an association between the Measles/Mumps/Rubella (MMR) vaccine and Autism spectrum disorders. The paper was later fully-retracted due controversy surrounding the lead author, who had financial conflicts of interest and allegedly manipulated the study data. However, it generated worldwide concern over the safety of MMR and other types of vaccines, including Diphtheria/Tetanus/Pertussis (DTP).

In California by 2010, the growing trend for parents to opt out of having their children receive vaccines over the following decade coincided with the largest Pertussis outbreak in more than 60 years. Reduced vaccination frequency was also linked to a high-profile measles outbreak in 2014 that began at Disneyland. The resulting California state legislation (Senate Bill 277), signed June 2015, made it much more difficult for parents to opt out of vaccinations for their children. The data set will allow you to explore individual public and private school vaccination rates of incoming Kindergarten students for the 2000 to 2014 school years.

Content

The data are records for every school with ten or more students reporting the number of incoming Kindergarteners who provided either proof of immunization, personal beliefs exemption (PBE), or permanent medical exemption (PME). Annual records for the 2000-2001 through 2014-2015 school years have been formatted and combined. Common variables in these annual data sets included in the merged file are the number of students, school name, school county, the number of PBEs, PMEs, and number of students vaccinated for:

• Diphtheria/Tetanus/Pertussis (DTP)
• Polio
• Measles/Mumps/Rubella (MMR)

One additional file contains 5 years of county-level Pertussis case numbers and rates. Another additional data file contains the number of infant Pertussis cases for infants under three months old for each county in California between 2014-2015.

Geographic data are available in a file based on scripted geocode calls using the ggmap R package to find latitude and longitude data using the school names and county names. Not all calls returned a valid coordinate, so additional indicator variables in this file indicate the quality of the match. The isSchool indicator variable is 1 if the geocode search meta data included "school" and the countyMatch indicator is 1 if the latitude and longitude coordinates are contained within the appropriate county in CA.

References:

1. Retracted Lancet Research Article
2. Report on 2010 Pertussis Outbreak

Acknowledgements

Individual data files and detailed annual reports for every school year in this data set are provided by the California Department of Public Health (CDPH). Individual schools and licensed child care facilities are required to report immunization information to CDPH every year to maintain compliance with the California Health and Safety Code. Additional details as well as child care and 7th grade data files can be found on the CDPH website: https://www.cdph.ca.gov/programs/immunize/Pages/ImmunizationLevels.aspx

County level case data were pulled from the following report: https://archive.cdph.ca.gov/programs/immunize/Documents/Pertussis_Report_1-7-2015.pdf

Infant Pertussis data were reported to CDPH as of 2/10/2016. Additional Pertussis reports can be found here: https://www.cdph.ca.gov/programs/immunize/Pages/PertussisSummaryReports.aspx

Inspiration

While the Disneyland measles outbreak received much media attention, Pertussis outbreaks in California present great health risks to infants and the elderly. Can you predict which counties and schools are at greatest risk for outbreaks and/or quantify the association between vaccination rates and the number infant Pertussis cases?

The annual pre-kindergarten (pre-K) through 12th grade school immunization survey collects school-level, grade-specific data on vaccine coverage and exemptions. The survey collects vaccination and exemption status data on children who entered the school system on or before a specified date during the fall semester. Individual vaccine information on each student is not collected. This table shows the vaccination exemptions (medical and religious) and percentage vaccinated and compliant for each school-entry mandated vaccine series reported by school year, county/county equivalent, and grade. In 2022, Connecticut began the process to adopt the State's nine planning regions as county-equivalent geographic units for the purposes of collecting, tabulating, and disseminating statistical data, replacing the eight counties. The data from the 2024-2025 school year is the first to reflect this change.* Percentage of students vaccinated is the number of students with the required number of doses of a given vaccine divided by the total number of students. Data for each grade includes all schools who reported with that given grade level. School-mandated vaccine series for students enrolled in kindergarten are inactivated polio, DTaP (diphtheria, tetanus, and acellular pertussis), MMR (measles, mumps, and rubella), hepatitis B, varicella and hepatitis A. Additional mandated vaccines for students enrolled in 7th grade include meningococcal conjugate vaccine (MCV) and Tdap (tetanus, diphtheria, and acellular pertussis). Influenza vaccine is a requirement for pre-K students only, who are 24 through 59 months of age. Each child has 1 of 4 possible vaccination statutes: Vaccinated, Exempt (Religious), Exempt (Medical) or Non-compliant. The criteria shown below are used to assess whether a child is considered vaccinated. • Flu = at least 1 dose of annual influenza vaccine (pre-K only). This is a school entry requirement only for pre-K students 24 through 59 months of age. • Polio = at least 3 doses of inactivated polio vaccine, with the last dose on or after their 4th birthday. This is a school entry requirement starting in kindergarten. • DTaP = at least 4 doses of DTaP vaccine, with the last dose on or after their 4th birthday. This is a school entry requirement starting in kindergarten. • MMR = at least 2 doses of MMR vaccine separated by at least 28 days, with the 1st dose on or after their 1st birthday. This is a school entry requirement starting in kindergarten. • HepB = at least 3 doses of hepatitis B vaccine, with the last dose on or after 24 weeks of age. This is a school entry requirement starting in kindergarten. • Varicella = at least 2 doses of varicella vaccine separated by at least 28 days, with the 1st dose on or after their 1st birthday, or a reliable history of chickenpox disease. This is a school entry requirement starting in kindergarten. • HepA = at least 2 doses of hepatitis A vaccine, given a minimum of six calendar months apart, with the 1st dose on or after their 1st birthday. This is a school entry requirement starting in kindergarten. Starting with the 2019-2020 school year the annual survey included data collection on hepatitis A vaccine for 7th grade students. • MCV = at least 1 dose of meningococcal conjugate vaccine. This is a school entry requirement starting in 7th grade. • Tdap = at least 1 dose of Tdap vaccine. This is a school entry requirement starting in 7th grade. • All = Percentage of students with all above vaccine series required for that grade level. Children without a record of vaccination, but with serologic proof of immunity to certain diseases (measles, mumps, rubella, hepatitis B, hepatitis A, and varicella), meet school entry requirements and may be counted as vaccinated. https://www.federalregister.gov/documents/2022/06/06/2022-12063/change-to-county-equivalents-in-the-state-of-connecticut https://portal.ct.gov/opm/igpp/org/planning-regions/planning-regions---overview Data Limitations a