Search for Pa. school vaccine rates

The Post-Gazette has created a portal that allows readers to search the vaccine rates of more than 3,000 public and private schools across the state — the first comprehensive database of its kind in Pennsylvania — to better inform the public about the levels of protection against diseases like measles.

The search engine also includes the percentage of students who’ve been exempted from vaccinations because of religious or philosophical objections to the shots.

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See related story:

Immunity Lost: How Pennsylvania’s falling school vaccination rates and enforcement failures put thousands of children at risk

Data last updated: 2024-2025 school year

Herd immunity

The percentages below show the immunization rates for a range of vaccines that are required by the state.

For each disease, medical experts say that a certain percentage of people need to be immune (either through vaccination or natural infection) to achieve herd immunity – the minimum threshold needed to stem the spread of the illness.

Experts say such numbers serve as general guidance, and the level of immunity needed to prevent the spread of disease can vary depending on several factors within each community.

Those variables can include population density, commuting patterns and whether children attend classes or are home-schooled. Typically, the herd immunity threshold is higher for infections that are more easily passed from person to person. A greater percentage of the population has to be immune to reduce or stop the spread of the more contagious diseases.

Herd immunity thresholds:

Disease	Herd immunity threshold
Measles	95%
Mumps	85% - 92%
Rubella*	83% - 86%
Varicella**	86% – 91%
Polio*	About 80%
Diphtheria*	80% – 85%
Pertussis***	90% - 94%
Tetanus	No herd immunity: Not contagious and can’t be passed from person to person.
Hepatitis B	No standard threshold; not spread through regular classroom contact

*Few cases of these diseases are reported each year, according to the Centers for Disease Control and Prevention. But public health experts say they can still be imported through international travel.

**Commonly known as chickenpox

***Multiple academic studies provide the herd immunity threshold for pertussis at between 90-94%. The Department of Health and Human Services set a target for 90%.

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Sources

Herd immunity rates for measles, mumps, rubella and varicella are from the CDC. Polio and diphtheria rates are from the World Health Organization.

The Post-Gazette consulted the following medical experts on herd immunity rates: Dr. Lori Handy, associate director of the Vaccine Education Center at Children’s Hospital of Philadelphia; Dr. Mark Roberts, former director of the Public Health Dynamics Lab at the University of Pittsburgh School of Public Health; and Mary Krauland, research professor at the University of Pittsburgh School of Public Health and a member of the school’s Public Health Dynamics Lab.

The Post-Gazette filed public records requests with the state Department of Health for vaccination rates at more than 4,500 schools. State health officials will not release records for about 1,400 schools – about one-third – in which fewer than 20 students are enrolled in classes for kindergarten, 7th grade or 12th grade, claiming such disclosure could risk identifying individual students.