But at home, resistance to vaccination was often intense. Willrich clearly portrays both sides in the debate: the progressives, confident in their science and determined to do good; and the anti-vaccinationists, who had strong scientific and political reasons to reject state coercion.

Politically, the anti-vaccinationists had a lot to work with. In one tragic case, working-class children in Camden, New Jersey, were vaccinated so they could attend public school. Many of them then died horribly of tetanus, which the parents blamed on the vaccinations. The government was obliged to check the origins of the vaccine and found that it was indeed contaminated.

The rise of Big Pharma

Incidents like these led to a decisive shift: Governments already saw themselves as possessing "police power" to enforce vaccination even against the individual's wishes. Now they saw this power extending to the makers of vaccines and pharmaceuticals. In 1902, president Theodore Roosevelt signed into law the Biologics Control Act. It drove the small vaccine producers out of business. From then on, only well-capitalized companies could meet the government's hygienic standards, and Big Pharma was born.

So was Big Government, which now demanded the vaccination of soldiers, prisoners, immigrants and many others far from the nearest smallpox outbreak. As Willrich says, "During the turn-of-the-century epidemics, millions of ordinary Americans could not enter their work sites, send their children to public school or travel freely without showing their vaccination scars."

Safer vaccines were not enough. Many Americans believed the government simply had no business forcibly injecting a disease into their healthy bodies. Anti-vaccination groups sprang up across the country. They often included exponents of what we now call "alternative" medicine: homeopaths, chiropractors and practitioners of now-forgotten therapies. Opposing vaccination helped them keep patients.

But the strongest opposition was based on philosophical grounds: The right of the individual to control over his or her body. In the spring of 1902, Henning Jacobson, a Swedish pastor in Cambridge, Massachusetts, refused to be vaccinated. The fine was five dollars, a sizable amount in those days. But Jacobson appealed -- and took his appeal all the way to the U.S. Supreme Court.

Jacobson v. Massachusetts was a pivotal case in American law, and reverberated for decades. The decision was handed down by John Marshall Harlan, a former slave holder. But he had been a loud dissenter in Plessy v. Ferguson, which had entrenched "separate but equal" Jim Crow. He was also a Progressive, often supporting the government's right to break up business trusts.

The limits on police power

Harlan's majority opinion upheld the police power of the state, with some limits. Jacobson had to pay his five dollar fine, but forcible vaccination was now forbidden. More importantly, the police power soon led to severe restrictions on personal liberty during the First World War and in the Red Scare following it. It also authorized horrors like eugenics laws that would later inspire the Nazis.

But after the Second World War, Harlan's limits on police power began to gain traction. In cases involving civil liberties and women's rights, his basic support for the right to bodily autonomy and integrity was the foundation for reproductive rights and sexual privacy.

A century later, we still battle over these issues. Measles and mumps outbreaks stem from parents' decisions not to vaccinate their children. Other parents blame vaccination for their children's autism. A large minority of health-care workers refuse to get flu shots. But smallpox is gone, and polio is almost gone. Vaccines have enabled many of their opponents to live long enough to oppose them.

The police power remains a vexing question for both the U.S. and Canada. It put troops in Little Rock to enforce school integration, but it also put Quebecers in jail during the October Crisis. And we still persist in the old Progressive dream of imposing our politics on other countries whether they want it or not.

Michael Willrich has thrown useful light not only on the pox and politics of a century ago, but on our present state of affairs, which is as conflicted as ever between public power and personal freedom.

[Tags: Health, Rights and Justice]