US — Boston University School of Public Health researchers published a study in the American Journal of Public Health on July 17, 2026, analyzing 1,513 state-level vaccine-related bills introduced between 2019 and 2023. The study found a significant increase in legislation aimed at reducing vaccine access, weakening vaccination requirements, and expanding exemptions after the pandemic began, with Republican lawmakers sponsoring the vast majority of these measures.

The study utilized data from the State Vaccine Policy Project, a database housed under The Politics and Health Lab at Boston University School of Public Health. Researchers examined legislative activity across all 50 states, categorizing bills as either antivaccine or provaccine based on their provisions. Antivaccine bills included those that sought to eliminate school or childcare immunization mandates, broaden nonmedical exemptions, or restrict employer vaccine requirements.

From 2021 to 2023, proposed bills aiming to reduce vaccine access, weaken vaccination requirements, and increase vaccine exemptions increased in state legislatures. In 2021 alone, 1,154 vaccine-related bills were introduced, a sharp rise from the 386 proposed during the 2019 legislative session. At least 40 percent of bills introduced in each full legislative cycle after the start of the pandemic were classified as antivaccine-related.

Republican lawmakers sponsored 86 percent of the antivaccine bills introduced between 2021 and 2023. During that same period, Democratic lawmakers introduced 54 percent of provaccine bills across state legislatures. When examining the full 2019–2023 timeframe, more than 65 percent of bills proposed by Republicans were antivaccine, while 28 percent were provaccine. In contrast, nearly 82 percent of bills proposed by Democrats were provaccine, and less than 10 percent were antivaccine.

Twenty-four percent of antivaccine legislation introduced between 2021 and 2023 received enough state legislative support to become law. Several states enacted laws expanding religious or personal belief exemptions for childcare and school immunizations during this period. Other states passed measures prohibiting employers from mandating certain vaccinations in the workplace.

"Our work shows that state lawmakers affiliated with the Republican party are responsible for the overwhelming majority of antivaccine bills introduced in recent years," said Matt Motta, associate professor of health law, policy & management at Boston University School of Public Health. Motta, who co-directs The Politics and Health Lab with Timothy Callaghan, emphasized the public health implications of these trends.

"While the majority of these bills do not actually pass, it's important to remember that we live in an increasingly connected and globalized world—one in which low vaccine coverage in one part of the country can get people sick thousands of miles away," Motta said. He added, "Weakening vaccine regulations in one state puts everyone's health at risk, as the current measles outbreak demonstrates.

Timothy Callaghan, also an associate professor of health law, policy & management at Boston University School of Public Health, noted that the proliferation of such legislation reflects more than just policy disagreement. These antivaccine bills not only signal the discontent that some have with vaccines, but also the more hostile policy environments towards vaccination, he said.

Both researchers stressed the importance of public health communication. Nobody likes being told what to do. But our government has the ability and obligation to take actions that protect public health, he said. Addressing those who oppose vaccination on moral or religious grounds, he added, Infectious disease has no sense of morality or religious creed.

Motta further argued that vaccination empowers individuals: Taking action to protect yourself and others is one of the safest and most effective actions you can take to live your life the way you want it," he said. "Vaccination is a way to take your freedom back from the pathogens that have caused sickness and death for all of human history.

Callaghan highlighted the complexity of rebuilding trust in science. We need to recognize that the reasons people lack trust in science are multifaceted, and that there isn't a one-size-fits-all solution that will work in restoring trust, he said. He emphasized the role of communication: We must also recognize that messengers matter as much, if not more, than the message.

Public health officials may not always be the most effective advocates, Callaghan noted: For public health, that also means recognizing that public health officials are not always going to be the right messengers to encourage vaccine uptake. He called for greater investment in research to identify effective strategies: Identifying the correct messages and messengers will take considerable investment in vaccine communication research, which is currently severely underfunded.

Motta outlined the broader research goals behind the study. Our hope is to provide researchers with a large, up-to-date database cataloging health policy legislative activity across the states, so that we can study how changes in our social and political worlds impact health policy, and how changes in health policy impacts public health," he said.

The State Vaccine Policy Project, which provided the data for this analysis, is maintained by The Politics and Health Lab at Boston University School of Public Health. Researchers intend to expand the dataset to analyze vaccine legislation over a larger period of time, enabling deeper longitudinal studies of policy trends.

The study documents a significant shift in state-level vaccine policy debates following the onset of the pandemic, with antivaccine legislation becoming increasingly common and largely concentrated within one political party. The passage of nearly a quarter of these bills into law has tangible consequences for public health, including weakened immunization requirements in schools and restrictions on workplace vaccine mandates. These changes occur against the backdrop of ongoing disease outbreaks, such as measles, which public health experts link to declining vaccination rates.

The findings also highlight a growing partisan divide in health policy, with implications for national disease prevention efforts. Because infectious diseases do not respect state borders, localized policy changes that reduce vaccine coverage can undermine herd immunity across regions. The researchers’ call for improved communication strategies and better-funded public health messaging reflects a recognition that legislative trends are intertwined with public trust and scientific literacy.