As the risk of measles remains an ongoing concern, herd immunity in Allegheny County, Pennsylvania, is already slipping. According to data obtained via The Washington Post in January 2026 , 1 in 3 Allegheny County kindergartners were in a classroom too far below adequate vaccination coverage to stop a measles outbreak during the 2023-24 school year.
A professor from the University of Pittsburgh's School of Public Health, Kar-Hai Chu , and a research program supervisor, Maggie Slavin , answered our questions about declining measles, mumps and rubella vaccination rates and what it means for the future of public health .
Private and parochial/religious schools in Allegheny County fall below the herd immunity threshold, while public schools tend not to. What explains that gap, and should it concern us?
Research shows the disparity between vaccination coverage in private and parochial/religious versus public schools is that private and parochial/religious schools tend to have higher rates of exemptions to vaccinations for moral and religious beliefs.
Local vaccination rates in Allegheny County schools are declining and are below the necessary level of vaccination coverage to stop the spread of measles: 95%. Between the 2023-24 and 2024-25 school years, public schools displayed an overall decline in coverage, whereas private and parochial/religious increased coverage between the two years, yet have greater variation in coverage across schools. Regardless of school type, children should have complete and updated vaccinations to protect themselves and the community. Even small dips in vaccination rates can lead to the spread of disease.
What are combination vaccines and how long have they been used?
Combination vaccines are single injections that protect against multiple, preventable diseases and have been used since the 1940s. They represent one of public health's most successful interventions . Common examples include DTaP - for diphtheria, tetanus and pertussis - and MMR , for measles, mumps and rubella. The MMR vaccine has been licensed since 1971 and helped eliminate measles from the U.S. by 2000 . It reduced cases by 80% within a decade of its introduction to society.
Why are some government officials calling to split these vaccines?
The U.S. officials calling to split combination vaccines cite unsubstantiated claims linking them to autism and concerns about too many vaccinations administered at once.
These claims contradict decades of scientific evidence that demonstrates the safety and efficacy of combination vaccines.
Who determines vaccination recommendations in the US?
Since 1964, the Advisory Committee on Immunization Practices has provided evidence-based vaccination recommendations. The committee consists of volunteer medical and public health experts appointed by the secretary of Health and Human Services for staggered, four-year terms. These experts review scientific evidence throughout the year and update recommendations accordingly. States maintain authority to implement these recommendations as they see fit. Vaccination recommendations have been politicized under the current administration and are currently in a sort of limbo.
In June 2025, HHS Secretary Robert F. Kennedy Jr., who has a history of promoting anti-vaccination dissinformation , took the unprecedented step of firing all 17 committee members and appointing 12 new members with questionable qualifications and conflicts of interest. This could be considered a fundamental disruption to the evidence-based process that has protected public health for over 60 years.
The Pennsylvania Department of Health and Gov. Josh Shapiro have stated that they continue to endorse evidence-based vaccination guidelines from leading national medical associations, such as the American Academy of Pediatrics, American Academy of Family Physicians and American College of Obstetricians and Gynecologists.
What are the real-world consequences of vaccine misinformation and disinformation?
An example consequence is now visible: Measles is spreading again in the U.S. In 2025, there were 2,255 confirmed cases , which is nearly double the 2019 peak of 1,274 cases .
While there haven't been any confirmed cases of measles in Allegheny County in 2026, there were confirmed measles cases in Lancaster County on Feb. 3, according to the Pennsylvania Department of Health, which determined the individuals were not vaccinated.
Another visible consequence of vaccination misinformation and disinformation is that unvaccinated people face 140 times higher risk of contracting measles . Over 90% of 2025 cases in the U.S. occurred in people who were unvaccinated or had unknown vaccine status.
When government officials become sources of misinformation , the threat multiplies exponentially . The World Health Organization identifies vaccine hesitancy as one of the biggest threats to global health.
What can be done to protect evidence-based vaccination policy?
The American Academy of Pediatrics emphasizes that state-level policies may offer greater responsiveness to local needs while maintaining evidence-based standards.
Stronger state policies play a key role in ensuring vaccine access. In Louisiana, for example, framing vaccination as a way to keep your neighbors safe has been used as an effective way to appeal to local communities. In South Dakota, advocates are reaching business owners by emphasizing the economic benefits of immunization. The state of Oregon created a financing model that allows providers and clinics to access vaccines with no upfront costs, then they reimburse the state once they have been paid by insurers.
People can support organizations that prioritize scientific evidence over anecdotes, demand transparency in policymaking and understand the difference between legitimate scientific debate and coordinated misinformation. These are crucial steps in protecting vaccine policies. The 2026 American Academy of Pediatrics guidelines have been deemed trustworthy by 12 health care organizations that represent over a million pediatric medical professionals.
Kar-Hai Chu receives funding from the NIH.
Maggie Slavin does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
