<Note: the below answer contains images that show the typical symptoms of smallpox, as well images of the rare adverse reactions to the smallpox vaccine. These images are not pleasant, so please skip this answer if you do not wish to see them.>
All medical procedures carry inherent risks, as well as potential benefits. While
some other interventions, e.g. surgery or anaesthetics, are relatively high risk compared to vaccines, vaccines still carry risks.
Back at the turn of the 20th century, those risks were considerable more severe than they are in modern times. The smallpox vaccination has a 95% success rate. It was probably lower in the 1900s, but it's unclear how much lower.
Vaccines are exceptional in that while the risks of being vaccinated are individual, the benefits are public as well as individual. An person who contracted a contagious illness because they are unvaccinated can infect other people. Someone who received a successful vaccination cannot spread said illness.
Contrariwise, an unvaccinated person still benefits from the vaccination of others. There are fewer vectors (i.e. ill people) to infect them. We can see a kind of game theory dynamic going on here: I might calculate that I should just let all these other people get vaccinated and I'll still probably be fine. I'm especially likely to make that calculation if, rightly or wrongly, I perceive the risk of said vaccination to be relatively high.
It's worth explaining why smallpox was considered such a serious problem by the government, and by a majority of the public whether rich or poor (you can see in one of the sources below that after the vaccine became voluntary, it still had a 75% compliance rate). In England, smallpox had been the cause of one in every thousand deaths at its highest points in the nineteenth century. This was not exceptional. In 1871, one of its worst years, smallpox was the cause of death 2.4 times out of every thousand in Prussia, and in Belgium and the Netherlands it killed over four of every thousand dead. You can find these statistics here; they also show a significant decline in smallpox deaths in England during the period of widespread vaccination.
You can see typical symptoms of the disease here:
Survivors of the disease were often marked by it for life:
To return to your question, the government may have calculated that, in an environment where most people did not object to receiving the smallpox vaccine, it was no longer necessary that the vaccine be mandatory in order to achieve a lower death rate among the population. The graph on this page a quarter of the way down shows that from 1880 to 1900, smallpox deaths per 1000 in England were considerably lower than in previous decades.
Today the list of side effects for the most modern smallpox vaccine:
More common: Feeling unusually cold, shivering, swollen, painful, or tender lymph glands in the neck, armpit, or groin
Less common: Agitation, [very long laundry list], wheezing.
Inoculation with vaccinia virus is highly effective for the prevention of smallpox infection, but it is associated with several known side effects that range from mild and self-limited to severe and life-threatening.
– Edward A. Belongia: "Smallpox Vaccine: The Good, the Bad, and the Ugly", Clin Med Res. 2003 Apr; 1(2): 87–92.
Concerns over poor hygiene in vaccinations for poor people in England are detailed below.
In 1898 after 45 years of enforcing mandatory infant smallpox vaccinations, the British parliament passed an act to allow parents to "opt out" of the compulsory system.…
This provided working- lower-middle-class antivaccinationists a measure of relief from the repeated fines they had suffered for noncompliance with the law, and from the threat of imprisonment. By the end of 1898, over 200,000 certificates of conscientious objection had been issued. Many of these were granted in antivaccination strongholds where exemptions outnumbered vaccinations, but conscientious objection to vaccination was by no means limited to these regions. Once an amended conscience clause was passed in 1907, which made conscientious objector status much easier to attain, the national exemption rate grew to 25 percent of all births.
Infant smallpox vaccination was made compulsory in England and Wales under a series of laws passed in 1853, 1867, and 1871. For those who could not afford the services of a private practitioner, vaccination was performed by state-paid vaccinators at public stations. At vaccinator stations vaccine matter was transferred directly from one child to another and with it, parents routinely complained, a variety of other diseases.
The arm-to-arm method thus provoked profound fears of blood pollution and bodily contamination. As it was administered by the Poor Guardians, whose vaccination officers could prosecute parents who did not comply with the law, compulsory vaccination epitomized what was considered the tyrannical policies of an increasingly interventionist Victorian state. For over fifty years an organized antivaccination movement successfully incited hundreds of thousands of largely, though not exclusively, working-class "citizen-parents" to resist the vaccination of children.
In a letter to the East London Observer in 1876, the antivaccinator and medical reformer John Stephens argued that the "medical monopoly," which included state-paid public vaccinators, deprived freemen of their civil rights and privileges".
– Nadja Durbach: "Class, Gender, and the Conscientious Objector to Vaccination, 1898-1907", J of British Studies, 41,1, 2002, pp. 58–83.
Eczema vaccinatum is a rare severe adverse reaction to smallpox vaccination. A vaccinated person can spread it to innocent people who have not been vaccinated. This was the cause of the symptoms in the image below.
Src: (PHIL), identification number #3311. CDC/Arthur E. Kaye,
This 8 mo. old boy developed eczema vaccinatum after he had acquired vaccina from a sibling recently vaccination for smallpox.
More direct effects of vaccine can look like this:
– "Smallpox: Dead or Alive?" Duke
It's pertinent that while an adverse reaction to a vaccine is obvious, the benefits of being vaccinated are less easy to distinguish. How can I know if it was the vaccine that prevented me from contracting the disease? I don't know for certain that I would have got the illness if I hadn't been vaccinated. See this article for more context.
– R.E. Spier: "Perception of risk of vaccine adverse events: a historical perspective", Vaccine, 20, (2002) S78–S84
Vaccines are never free of risk, despite them supposedly getting better all the time.
The mistake produced […] live polio virus. Of children […] 40,000 developed abortive poliomyelitis […] 56 developed paralytic poliomyelitis—and of these, five children died from polio. The exposures led to an epidemic of polio in the families and communities[…] resulting in a further 113 people paralyzed and 5 deaths.
– "Cutter incident" 1955
For English smallpox vaccination we see also the effect that "saving money" produces another problem, distinct from side-effects and political ramifications: plainly chaotic organisation and incompetent personnel:
Seaton told of a highly qualified medical practitioner who, according to his own account, ‘could not make his vaccination succeed more than 4 times out of 5’. What the quality of private vaccination was like no one seemed either to know or care.
In the meantime inspectors had a benchmark against which to assess the state of the nation’s arms, or at least those of its children, after nearly a decade of compulsory vaccination. Their annual reports justified the worst accusations of its critics:
- Not one tenth part of the vaccinated children had that all but complete protection which four proper scars have been found to give.
- In Dowlais, in the union of Merthyr Tydfil […] the vaccination of children of 3 to 7 years of age was scandalously bad. Some […] was nothing more than a sham.
- Only 3% [of children] had four typical cicatrices, 6.8 had three equally good, 26.7 had two, 25.5 had one, 15 were quite unprotected; and the amount of [their] immunity from death was very slight. (Stevens: Derbyshire, Shropshire, Staffordshire)
- In a village in Gloucestershire, where vaccination has long been performed by an unqualified assistant, almost all the children in the school exhibit unsightly oblong scars such as might have been produced by an instrument having a blunt jagged edge. In a neighbouring town […] the scars were in general not only very small, but so far from typical that they could scarcely be recognised as vaccination scars at all.
Such critics pressured the government into action:
The anti-vaccinationists capitalized on the outbreak in Sheffield by demanding that the Home Secretary appoint a Royal Commission, and in what has been described as a volte-face (possibly influenced by events in Sheffield) the President of the Local Government Board, Henry Chaplin, granted the request, not, he insisted, ‘because [the government] have the slightest doubt of the efficiency of vaccination, but because the state of public opinion requires that a thorough investigation should be made into the whole question’.
The most notable event during the seemingly interminable inquiry occurred with the publication of the fifth of the Commission’s annual interim reports, which broke away from the laconic one-sentence format of its predecessors ‘to make recommendations with respect to certain subsidiary questions to which our attention has been drawn’. The first recommendation, which could be said to arise from the fifth of the questions set out in the Commission’s remit, recalled the events of 1871 by virtually accepting the conclusion of the select committee of that year embodied in the clause that the House of Lords had succeeded in removing from the ensuing Act. The Royal Commission’s recommendation was that ‘the imposition of repeated penalties in respect of the non-vaccination of the same child should no longer be possible’. The justification given for the change was that ‘any advantage which may arise from the tendency of repeated convictions to increase vaccination is more than counterbalanced by the resentment and active opposition to vaccination which they engender’.
The second recommendation addressed a more serious abuse – the treatment of parents who, having refused or been unable to pay fines, had been given a prison sentence. Accounts of their experiences, even allowing for some excusable exaggeration, revealed regimes of severity and harshness that were out of all proportion to the offence, and were due, in the Commission’s opinion, to a deliberate misreading by the Home Secretary of the Prisons Act, which stated explicitly that ‘[i]n a prison where debtors are confined means shall be provided for separating them altogether from the criminal prisoners’. The Home Secretary had decided that this should not apply to those imprisoned under the Vaccination Acts for non-payment of fines. The Commission now recommended firmly that ‘persons imprisoned under the Vaccination Acts should no longer be subjected to the same treatment as criminals’, but should be treated as ‘simple imprisonment prisoners’, and were therefore ‘not to be sentenced to hard labour’. The Commissioners’ reasoning was that ‘many of those whose imprisonment arises from the contravention of the laws relating to vaccination regard the practice as likely to be injurious to the health of their children, and are well conducted and in other respects law-abiding citizens’. Subjecting them to the treatment awarded to criminals was not ‘calculated to secure obedience to the law or to add to the number of the vaccinated’.
Both recommendations, although rationally defended and based on more than thirty years’ experience of the failure of the existing system, were predictably and bitterly attacked by hardliners in the compulsion camp, but for those shrewd enough to read between the lines they provided a clear pointer to the spirit of the conclusions that the Commission was likely to reach in its final report. Owing to confusion among the anti-vaccinationist leaders, and an unfortunately timed change of government, a Bill that was intended to give effect to the Commission’s recommendations made no progress.
The Commission’s final report was issued in 1896 (with a dissenting report written by Collins and J. A. Picton, a Methodist minister who, as the anti-vaccinationist candidate at a by-election in 1884, had been returned unopposed as one of Leicester’s two MPs). It offered something less than the anti-vaccination lobby had hoped for and far more than the pro-compulsion medical and political establishments had expected to have to concede. It made numerous recommendations, of which the main ones were that vaccination should continue to be compulsory but that parents who could demonstrate a conscientious objection to having the operation carried out on a child should not be compelled to do so. This concession, as was furiously pointed out, could and probably would undermine the whole purpose of the Vaccination Acts. […]
A Bill incorporating most of the Commission’s proposal but not the significant concession of a conscience clause was introduced by Henry Chaplin. After a great deal of political infighting and bargaining a compromise proposed by Balfour, which stopped short only of the abolition of compulsion, secured the passage of the Vaccination Act of 1898. By a remarkable irony this argument took place against the background of the last major epidemic of smallpox to occur in Britain. Under the leadership of the proprietor of a local newspaper the city of Gloucester had almost completely abandoned vaccination, until 1896, when an outbreak of smallpox in one area spread rapidly, as much as anything because facilities for dealing with it were grossly inadequate.
– Stanley Williamson: "The Vaccination Controversy. The rise, reign and fall of compulsory vaccination for smallpox", Liverpool University Press: Liverpool, 2007.
On a large enough scale for populations and time, the benefits of mass vaccination may be clearer. But these benefits may only outweigh the dangers from a public health perspective. It does not eliminate the dangers any vaccinations carry.
–– Hervé Bazin: "The Eradication of Smallpox. Edward Jenner and the First and Only Eradication of a Human Infectious Disease", Academic Press, 2000.
–– James C. Frauenthal: "Smallpox. When Should Routine Vaccination Be Discontinued?", Birkhäuser: Boston, Basel, 1982.