Republican Lawmakers Sponsored 86 Percent of Antivaccine Bills Introduced in US States Since the Pandemic

In 2021 a Republican legislator in Idaho introduced a bill that would have made it a form of bodily assault to require a vaccine as a condition of work or school. Not a fine. Not a civil penalty. Assault, the same statutory category as hitting someone. The bill died, as most bills do, and would have been an odd footnote were it not for the fact that lawmakers in other states were reaching for much the same lever at much the same time.

Montana, for instance, actually passed a law restricting employers from requiring vaccination, and a federal judge later struck it down. Idaho and Montana looked, for a while, like outliers.

They were not. A new analysis in the American Journal of Public Health has put numbers to what had until now been a pile of anecdotes and news clippings: since COVID-19 vaccines arrived, US state legislatures have been flooded with vaccine bills, and a large and growing share of them are designed to weaken vaccination rather than promote it. Matt Motta and Timothy Callaghan, both at Boston University School of Public Health, built a data set of 3,574 vaccine-related bills introduced across all fifty states between 2019 and 2023, coded one at a time by hand. The raw crawl turned up 6,426 candidate bills mentioning some variant of the word vaccine. Graduate student coders then worked through them, deciding case by case whether each bill increased access, funding and promotion, or cut them.

The volume alone is striking. In 2019 state legislatures introduced 386 vaccine-related bills; in 2021, the first full session after the vaccines rolled out, they introduced 1,154.

The Asymmetry Nobody Had Measured

What Motta and Callaghan were really after, though, was direction. Polarization can be symmetrical: both sides get louder, and the net effect on policy is roughly nil. That’s not what the data show. Of the 1,513 bills the team coded as antivaccine, 86 percent had a Republican primary sponsor. Roughly two-thirds of everything Republicans introduced was antivaccine in focus, against 28 per cent that was provaccine. Democrats went the other way, with about 82 percent of their bills promoting vaccination and fewer than one in ten opposing it.

“Our work shows that state lawmakers affiliated with the Republican party are responsible for the overwhelming majority of antivaccine bills introduced in recent years,” says Motta.

The obvious objection is that this is really a story about which party happens to control which statehouse. Red states pass red bills; the sponsor’s own party affiliation might be incidental. So the team ran a model holding state political context constant, testing whether Republican control of the lower house, the upper house or the governor’s office explained the pattern. It mostly did not. Sponsorship by a Republican was associated with a 55-percentage-point jump in the likelihood that a given bill was antivaccine, and that effect held steady regardless of who ran the building. Republican control of a state senate added another nine points. Control of the lower house and the governor’s mansion added nothing statistically distinguishable from zero. It’s the individual legislator, in other words, not the chamber.

Most of these bills go nowhere, which is the usual fate of legislation everywhere. Of the vaccine bills that were adopted, provaccine measures made up 65 percent and antivaccine measures 24 percent, so the filter is doing something. But 138 antivaccine bills did become law, expanding religious and personal belief exemptions for school and childcare immunization, or barring employers from requiring shots.

What a Bill Signals Even When It Fails

A bill that dies in committee changes no one’s vaccination status. “These antivaccine bills not only signal the discontent that some have with vaccines, but also the more hostile policy environments towards vaccination,” Callaghan says. The researchers stop short of claiming that any of this has yet moved coverage rates; they say only that with nearly one in ten of the antivaccine bills in their data signed into law, the policy environment could plausibly shape future rates of protection against vaccine-preventable disease. They also concede a limitation: their crawl missed bills. Checked against a National Conference of State Legislatures database for 2023 to 2024, the project captured about 69 percent of the pooled total, though the gaps did not skew by party.

Motta frames the stakes geographically. Weakening rules in one state, he argues, does not stay in that state. “Weakening vaccine regulations in one state puts everyone’s health at risk, as the current measles outbreak demonstrates.”

Both researchers are alert to why the arguments hit home. Sponsors rarely present themselves as against vaccines; they present themselves as for medical freedom, parental rights, bodily autonomy. That is a formidable rhetorical position, and Motta doesn’t pretend otherwise. “Nobody likes being told what to do. But our government has the ability and obligation to take actions that protect public health,” he says, before making the case that vaccination is itself a way of reclaiming freedom from pathogens.

Callaghan’s diagnosis of the trust problem is bleaker and, perhaps, more useful. There is no single fix, he says, because the reasons people distrust science are not singular. And “messengers matter as much, if not more, than the message.” His conclusion is one that public health institutions may find hard to swallow: “public health officials are not always going to be the right messengers to encourage vaccine uptake.” Funding for the research that would identify better ones, he notes, is thin.

The team now wants to widen the data set backward in time and outward into other contested territory: gender-affirming care, reproductive health, water fluoridation. Whether the vaccine pattern generalizes is an open question.

Frequently Asked Questions

Are most antivaccine bills actually becoming law?

Most antivaccine bills are not becoming law. Among vaccine-related bills that were adopted between 2019 and 2023, provaccine measures accounted for 65 percent and antivaccine measures 24 percent. Even so, 138 antivaccine bills were enacted, several of which expanded religious or personal belief exemptions for school immunization or barred employers from requiring vaccination.

Is this just a case of Republican-controlled states passing Republican bills?

It is not just a case of Republican-controlled states passing Republican bills. When the researchers held state political context constant, a Republican primary sponsor was still associated with a 55-percentage-point increase in the likelihood that a bill was antivaccine, regardless of which party controlled the legislature or the governor’s office. Republican control of a state senate added a further nine points, while control of the lower house and governorship showed no statistically meaningful effect.

Why does a bill that fails still matter for public health?

A bill that fails still matters because it signals a more hostile policy environment for vaccination, according to study co-author Timothy Callaghan. Failed bills also indicate where future attempts are likely, and the researchers argue that low vaccine coverage in one part of the country can affect people far away, as with measles.

How did the researchers actually count these bills?

The researchers counted the bills by first crawling a legislative database for any bill mentioning a variant of the word vaccine, which produced 6,426 candidates, then having trained graduate student coders read and classify each one by hand. The final data set contains 3,574 vaccine-related bills from all fifty state legislatures covering 2019 through 2023. The team acknowledges the collection is not exhaustive, capturing roughly 69 percent of bills when checked against a separate legislative database.