At the turn of the 19th century, a Massachusetts doctor named Benjamin Waterhouse learned that an English physician had been injecting people with the cowpox virus and claiming it protected them from the deadlier smallpox. So Waterhouse decided to test this novel treatment on his 5-year-old son and expose him to smallpox patients.

At the time, it wasn’t unusual for scientists and doctors to use their children as test subjects. When Waterhouse’s son didn’t become ill, he vaccinated other members of his family. Then he raised the stakes.

He repeated the experiment — this time with 19 children. He injected them with cowpox and sent them to Noddle’s Island, a secluded smallpox hospital off the coast of Boston. Twenty days later, not a single one was showing symptoms of smallpox.

Waterhouse published his results within weeks of completing the experiment. He became a passionate vaccine advocate, lobbying every level of government, from the Boston Board of Heath all the way up to the White House, to demand an organized way to vaccinate the public. He even sent the vaccine to President Thomas Jefferson.

Armed with the results of Waterhouse’s experiments, alongside several conducted by other local doctors, the Massachusetts legislature took swift action. In 1809, it passed a law giving local health boards the authority to require vaccination — the first vaccine mandate law in U.S. history.

The law was initially ad hoc: The state remained predominantly rural, and the mandate was largely enforced — through fines or quarantine — when outbreaks occurred, according to Elena Conis, a historian of medicine at the University of California, Berkeley. Still, the same year the mandate passed, people across the state clamored to get vaccinated, according to local news reports at the time. As one newspaper wrote of the process in 1809: “It leaves behind no blemish, but a blessing; — one of the greatest ever bestowed on man; — a perfect security against the future infection of the small-pox.”

Reports from Boston and nearby towns often described the smallpox vaccine in reverential terms. The word “blessing” appears again and again in articles published at the time, which were collected by the genealogy company MyHeritage. One journalist for the Boston Gazette listed the smallpox vaccine among the great inventions of history, comparing its societal importance to those of gunpowder, the compass and the printing press.

The vaccine itself, and later the mandate, met with some resistance. That same Gazette article noted that some locals considered the vaccine “fallacious and equivocal.” A swath of the population was hesitant; early vaccines risked more severe side effects than current ones, including scarring around the injection site, and unsanitary needle practices meant that people could contract other diseases such as tetanus. The benefit, however, outweighed the risk for many Massachusetts residents who had lived under the threat of smallpox their entire lives.

“It doesn’t seem to have triggered widespread opposition at the time,” said James Colgrove, a professor of sociomedical sciences at Columbia University and author of “Epidemic City: The Politics of Public Health in New York.” “People were terrified of smallpox, and people’s own experience with vaccination reassured them. When smallpox outbreaks struck their area, people could see that those in their community who had been vaccinated didn’t get sick.”

The biggest hurdle was not that people did not want the shot, but that many did not have access to it. The procedure often required paying a small fee, and some poorer Bostonians could not afford it. Boston began setting up free vaccinations for those who could not afford to pay as early as the first decade of the 19th century.

While the 1809 law may have been the first vaccine mandate, it was hardly the first public health law of its kind, and similar requirements had been put in place for vaccination’s predecessor, inoculation.

“Mandates were not uncommon,” said Lawrence Gostin, a professor of global health law at Georgetown University. “Even George Washington ordered the inoculation of all of the continental troops. Smallpox was the dominant public health problem, and mandates weren’t foreign to the United States.”

Starting in 1827, all Boston children were required to show proof of smallpox vaccination to attend school. Massachusetts enacted a statewide requirement in the 1850s, and other states followed suit. By the end of the 19th century, 13 states required vaccination for schoolchildren, and 11 states had adult vaccine mandates.

The greatest challenge to Massachusetts’s vaccine mandates would come nearly a century after the initial legislation, in a case that would go to the highest court in the land. Massachusetts resident Henning Jacobson refused a mandatory smallpox booster vaccine in 1902, citing a bad reaction to his first shot several years prior. After he was fined $5 (the equivalent of approximately $153 today) for refusing to comply, local anti-vaccination activists picked up his case, eventually bringing it all the way to the Supreme Court.

In a 7-2 vote, the Supreme Court upheld the mandate and the state’s right to fine citizens who did not comply, though it also decreed that no one could be forcibly vaccinated. “[T]he liberty secured by the Constitution of the United States to every person within its jurisdiction does not import an absolute right in each person to be, at all times and in all circumstances, wholly free from restraint,” wrote Justice John Marshall Harlan in the majority opinion. With that, the mandate enacted nearly 100 years prior was affirmed as constitutional.

More than a century after that ruling, the country is again grappling with mandates and their constitutionality. Last month, President Joe Biden announced that starting in January, certain health care workers and employees of private companies with at least 100 employees would be required to be vaccinated against the coronavirus (with exemptions for companies that regularly tested employees). But those mandates were blocked in court and could end up being reviewed by the Supreme Court. Meanwhile, New York City has enacted its own local mandate, while on Wednesday, Senate Republicans voted to overturn Biden’s mandate for private-sector employees.

Just as at the turn of the 19th and 20th centuries, a legal and political contest is playing out between individual liberty and public health. It’s too soon to say whether the current courts will agree, as Justice Harlan wrote in 1905, that personal freedoms should never supersede “the common good.”

Jess McHugh’s book “Americanon,” a history of U.S. bestsellers, was published this year.