Smallpox was eradicated in 1977 thanks to a massive worldwide vaccination campaign. But how did the US government enforce the smallpox vaccine, given that you needed 90+% vaccinated to achieve herd immunity? I can find Supreme Court cases showing that mandatory vaccinations were allowed but how exactly were they enforced? Wikipedia contains the following passage:

In the United States, from 1843 to 1855, first Massachusetts and then other states required smallpox vaccination. Although some disliked these measures, coordinated efforts against smallpox went on, and the disease continued to diminish in the wealthy countries. In Northern Europe a number of countries had eliminated smallpox by 1900, and by 1914, the incidence in most industrialized countries had decreased to comparatively low levels.

But... what exactly did the states do to ensure vaccine compliance? Did local medical authorities go house to house injecting everyone with the vaccine without asking for consent?

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    Comments are not for extended discussion; this conversation has been moved to chat.
    – MCW
    Commented Sep 13, 2021 at 14:35
  • @Pere While we're at it, note that Wikipedia is a collection of written interpretations, not a source for itself. Please link to the source of the 80% itself instead.
    – Mast
    Commented Sep 14, 2021 at 15:35
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    @Mast The source is beyond a paywall nature.com/articles/414748a . However, I just wanted to highlight that the unsourced claim in the question that herd immunity = 90% vaccination is not true for all diseases, but just an estimate for Covid-19, or some of its variants.
    – Pere
    Commented Sep 14, 2021 at 15:40

5 Answers 5


After a brief period of federal control in the early 1800s, administration of the smallpox vaccine was mainly left to the states. Because of that, there is more than a century of different laws, mandates, and vaccination campaigns to sift through. To keep things simple, we can look at a few big court cases and outbreaks to get a general idea of what states did to eradicate smallpox through vaccination.

In short, smallpox vaccinations could be enforced among adults through fines for noncompliance, children were often required to be vaccinated to attend public school, and people were just generally encouraged or willing to get vaccinated to prevent or control outbreaks.

In 1813, Congress passed the Vaccine Act of 1813, which had half a sentence authorizing a federal agent to preserve the vaccine for any citizen who asked for it, and two paragraphs devoted to how that agent could use the postal system to distribute it:

...That the President of the United States be, and he is hereby authorized to appoint an agent to preserve the genuine vaccine matter, and to furnish the same to any citizen of the United States, whenever it may be applied for, through the medium of the post-office;

Unfortunately, it seems that in 1821 a doctor appointed as the federal agent caused an outbreak in North Carolina by accidentally sending a sample of smallpox rather than the vaccine, and the law was soon repealed.

For the rest of the 19th century, states implemented their own measures to control any smallpox outbreaks, including mandatory vaccinations in certain situations and different punishments for noncompliance. In 1905, Jacobson v. Massachusetts established that compulsory vaccine laws were constitutional, and the text of the decision provides a good overview of vaccine laws in Massachusetts at the time:

This case involves the validity, under the Constitution of the United States, of certain provisions in the statutes of Massachusetts relating to vaccination.

The Revised Laws of that commonwealth, chap. 75, § 137, provide that 'the board of health of a city or town, if, in its opinion, it is necessary for the public health or safety, shall require and enforce the vaccination and revaccination of all the inhabitants thereof, and shall provide them with the means of free vaccination. Whoever, being over twenty-one years of age and not under guardianship, refuses or neglects to comply with such requirement shall forfeit $5.'

In short, towns were allowed to require everyone to get a free vaccination, and adults who refused would be fined $5 (about $150 today). In 1902, the city of Cambridge enacted such a requirement:

Proceeding under the above statutes, the board of health of the city of Cambridge, Massachusetts, on the 27th day of February, 1902, adopted the following regulation: 'Whereas, smallpox has been prevalent to some extent in the city of Cambridge, and still continues to increase; and whereas, it is necessary for the speedy extermination of the disease that all persons not protected by vaccination should be vaccinated; and whereas, in the opinion of the board, the public health and safety require the vaccination or revaccination of all the inhabitants of Cambridge; be it ordered, that all the inhabitants habitants of the city who have not been successfully vaccinated since March 1st, 1897, be vaccinated or revaccinated.'

Subsequently, the board adopted an additional regulation empowering a named physician to enforce the vaccination of persons as directed by the board at its special meeting of February 27th.

The Supreme Court found this vaccination requirement to be within a state's power to enact, and in their decision they reference cases involving vaccinations as a condition to go to school:

And the principle of vaccination as a means to prevent the spread of smallpox has been enforced in many states by statutes making the vaccination of children a condition of their right to enter or remain in public schools. Blue v. Beach, 155 Ind. 121, 50 L. R. A. 64, 80 Am. St. Rep. 195, 56 N. E. 89; Morris v. Columbus, 102 Ga. 792, 42 L. R. A. 175, 66 Am. St. Rep. 243, 30 S. E. 850; State v. Hay, 126 N. C. 999, 49 L. R. A. 588, 78 Am. St. Rep. 691, 35 S. E. 459; Abeel v. Clark, 84 Cal. 226, 24 Pac. 383; Bissell v. Davison, 65 Conn. 183, 29 L. R. A. 251, 32 Atl. 348; Hazen v. Strong, 2 Vt. 427; Duffield v. Williamsport School District, 162 Pa. 476, 25 L. R. A. 152, 29 Atl. 742.

That list references cases in Indiana, Georgia, North Carolina, California, Connecticut, Vermont, and Pennsylvania, indicating that school children across the country were being vaccinated for smallpox, much like they are for a variety of diseases today.

These sorts of vaccination requirements helped control smallpox outbreaks, and by the 1950's smallpox was essentially eliminated from the US. The last major outbreak occurred in New York in 1947, when a couple returned to New York City from a vacation in Mexico. Eugene Le Bar had apparently been exposed to smallpox in Mexico, and caused a small outbreak that resulted in 12 confirmed cases and 2 deaths. As a result of these cases, a massive vaccination campaign was launched to prevent a larger outbreak. Vaccinations weren't required, but an ad campaign and door-to-door volunteers urged people to go to newly set up vaccination clinics, leading to most of the city being vaccinated within a few weeks.

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    "in 1821 a doctor appointed as the federal agent caused an outbreak in North Carolina by accidentally sending a sample of smallpox rather than the vaccine" - Whoops!
    – Vikki
    Commented Sep 14, 2021 at 22:27

It's hard to say how reliable this source is, but it is said in an interview with a history professor who wrote a book on the matter that in some cases more definite force was used:

The events of this time, known as the Progressive Era, paved the way for laws and regulations still in force today. Michael Willrich, the Leff Families Professor of History, chronicled this period in American history in his award-winning book, “Pox: An American History.” [...]

How was compulsory vaccination carried out in discriminatory ways?

Willrich: Ultimately, compulsory vaccination was carried out in many communities in a way that was discriminatory against African Americans and immigrant groups. There were examples of compulsory vaccination being carried out with force in immigrant tenement districts in cities like Chicago, New York and Boston. Local governments created “virus squads,” teams of police and vaccinators that cordoned off city blocks, entered neighborhoods in the middle of the night, and went door to door, checking people to see if they had vaccination scars proving they had recently been vaccinated. Police tore infected children from their mothers’ arms and took them to isolation hospitals called “pesthouses.”

I'm adding this because you asked "Did local medical authorities go house to house injecting everyone with the vaccine without asking for consent?" Unfortunately, the interview is not more detailed than that in that regard, like more concrete time frame and instances of such events. The book might have more in that regard.

Based on another source that uses the "virus squad" terminology (which I'm guessing it's a modern retrofitting), that seem to roughly refer to events around 1900:

The last epidemic of smallpox in Boston, Massachusetts began in 1901 and lasted for almost two years. A recent article (New England Journal of Medicine 2001;344:375–9) has described some of the excesses of medical fervour displayed in an attempt to control it.  The epidemic began in May 1901 and when it ended in March 1903 there had been 1596 cases and 270 deaths. Almost half (47%) of the cases had been vaccinated and in these the fatality rate was 11% whereas in unvaccinated patients it was 22%. In “public” (state) schools vaccination had been compulsory since 1855 and during the epidemic the rate of infection in children aged 6–10 years was about one sixth of that in pre-school children.  Initially, voluntary vaccination was offered but compulsory vaccination was introduced in December 1901. The penalty for refusing to be vaccinated was a $5 fine or 15 days in prison. Homeless and destitute people were thought to constitute a major risk to the rest of the population and men in cheap boarding houses were vaccinated forcefully by “virus squads”, often including three policemen to hold down the resisting tramp.

N.B. the 2001 longer article referenced is open access. It does say that force was at least not part of the official instructions (given to physicians)...

The instructions given to the physicians were as follows: “Vaccinate all who are willing and are not too ill. No force to be used.” [...] Persons who refused vaccination were subject to a $5 fine or a 15-day jail sentence.

But given how police was well known for "curbstone justice" at the time... a practice which persisted until much later... what was in the official instructions and what might have happened aren't necessarily the same thing. The NEJM article relates some of that by quoting the press of the time:

In November 1901, the Boston Board of Health ordered “virus squads” to vaccinate men living in inexpensive rooming houses.

A reporter for the Boston Globe accompanied a squad one night and described the scene: “Every imaginable threat from civil suits to cold-blooded murder when they got an opportunity to commit it, was made by the writhing, cursing, struggling tramps who were operated upon, and a lot of them had to be held down in their cots, one big policeman sitting on their legs, and another on their heads, while the third held the arms, bared for the doctors.” One “fighting tramp,” who “went down in a heap on the floor” from the blow of a policeman's club, received both vaccination and suturing of his scalp.

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    @JonathanReez: also "virus squads" is a modern term, since it was definitely not known through much of pox history that it even was a virus. That makes it hard to search for a relevant term to find other (historical) sources. Commented Sep 13, 2021 at 4:56
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    The term "virus" was in widespread use in all of the 19th century to mean "infectious agent", including both bacteria and what we now call viruses. (virology.ws/2019/08/22/the-evolving-concept-of-virus traces the shift in meaning of the word to the modern sense.) If you google-books search for 19th century "virus squad" you will find mention of vaccinating squads and collecting squads, as in google.com/books/edition/Yale_Medical_Journal/… . Commented Sep 14, 2021 at 11:39
  • Very interesting update! Looks like force was only applied to the homeless and everyone else was just nudged in other ways. Commented Sep 14, 2021 at 19:04

Let me first note that the percentage of vaccinated population necessary to achieve herd imunity varies with virus, but also with other factors, such as the density of population, nature of human interactions, etc.

Moreover, the herd immunity applies to populations that are being constantly exposed to a pathogen, meaning that isolated cases have negligeable chance to spread in the population. Smallpox existed only in human populations - unlike covid-19, influenza, Zika, Ebola and other viruses that we hear about today, which have animal reservoirs and/or transmitted by animals/insects. Thus, one needed to vaccinate those who were at risk of being exposed to already sick individuals, but not necessarily the whole population.

Note that this is also the strategy used today in respect to diseases that are not endemic to a specific region. E.g., tuberculesis is largely non-existent in most developed countries, so that vaccination is potentially more harmful/expensive than containing the small outbreaks. Thus, one vaccinates only those who could have been in contact with a knwon case or those who are traveling to areas affected by this disease.

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    This might be true but it doesn't address the question of how vaccinations were enforced in the U.S.
    – Steve Bird
    Commented Sep 15, 2021 at 6:12
  • @SteveBird I think this addresses the question in a different way: there was never need for enforcing 90% population to be vaccinated against the smallpox, just as there is no need to do it today.
    – Roger V.
    Commented Sep 15, 2021 at 7:30

According to this article, the authorities in some areas did literally go door-to-door to check whether people were vaccinated.

Isolation was also taken far more seriously. Infected people were not just trusted to self-isolate - often they were forcibly interned to keep them isolated. The case of Typhoid Mary is not at all atypical for the time; whilst a different disease, it demonstrates the lengths to which the authorities would go.

In short, the right to life for the majority was seen as far more significant than the right to personal freedom for an individual, in the case of a disease with a high probability of fatality. This balance naturally depends on the probability of death, the effectiveness of treatment, and the degree to which personal freedoms are curtailed; but in the case of infectious and frequently-fatal diseases like smallpox and typhus, and without modern healthcare, this was clearly the best they could do at the time.

  • Was it really respect for "the right to life" or simply less scrupulous understanding of "individual freedoms"? In even less recent past thousands of individuals were shipped overseas to risk their lives in wars that they didn't really care about.
    – Roger V.
    Commented Sep 17, 2021 at 15:18

In my state (Oregon) I was not vaccinated as a child but had to be vaccinated to enter a state university (1969).

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    Personal histories don't really have supporting documents. This answer is an important contribution, despite this comment. Commented Sep 14, 2021 at 10:57
  • In Chicago in the 40's , your grammar school class went to ( gym ?) and everybody got small pox vaccinations, period. White area ,which I doubt made any difference. What the documented histories miss is after the pustules formed at the vaccination spot some boys would try to break each others . Commented Sep 14, 2021 at 19:59

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