In due course the Duchess gave birth to six more children.
- Lady Jean Douglas-Hamilton born 11 June 1904.
- George Nigel Douglas-Hamilton, 10th Earl of Selkirk born January 4th 1906.
- Lady Margaret Douglas-Hamilton born 1907.
- Lord Malcolm Avondale Douglas-Hamilton, born November 12th 1909.
- Lord David Douglas-Hamilton November 8th 1912.
- Lady Mairi Nina Douglas-Hamilton born 24th August 1914.
On August 26th 1904, The Duke appeared at Wimborne Magistrates Court in Dorset to register his conscientious objection to the vaccination of his child and was granted his certificate of exemption. The word child is used advisedly, The Vaccination Inquirer and Health Review, the journal of the National Anti-vaccination League, refer to “…a little daughter…” and that the Duke had become a member of the Scottish Anti-Vaccination League.
However, the numerous newspaper reports refer to “…an infant son.” The following is an example taken from The Bellshill Speaker.
The Duke of Hamilton applied to the Wimborne magistrates on Friday for a certificate exempting his infant son from vaccination. The Chairman—Why do you ask for this? The Duke—I have objection to vaccination. The Chairman-Very well, it is granted. It should be added that in Scotland conscientious scruples would not entertained, but in England the vaccination laws are voluntary.
So, did the Duke claim exemption for his heir Douglas or his daughter Jean? Either is possible as in England and Wales, vaccination had to be performed by the time the child was three months old. Without reading the court documents or tracing the Registrar’s Vaccination Book it is impossible to identify which child was exempted. No earlier record of the Duke applying for exemption has yet been identified.
Whatever the gender of the exempted child, it certainly created something of a furore in Scotland. The law relating to conscientious objection which came into force in 1898 allowed parents in England and Wales to obtain a certificate of objection. However when the legislation was being considered by parliament, Scotland was specifically excluded from the legislation. Had these children been born at the family seat Hamilton Palace, Lanarkshire, the Duke would have been unable to claim an exemption from vaccination, as the conscience clause was not extended to Scotland until 1907.
In 1905, John H Bonner undertook a speaking tour of Scotland on behalf of the National Anti-Vaccination League, to “educate’ the people of Scotland about the “evils of vaccination”. One of the locations where Bonner spoke was at Hamilton and Bonner’s account comments
At Hamilton we assembled within half a mile of the Duke’s palace, and the fact that his Grace had been enabled to apply for, and obtain, an exemption certificate considerably impressed the local people. I was informed that in all probability the attention of the Duke was attracted to our question through an employee on his estate having suffered a term of imprisonment a year or two ago.
A search of The British Newspaper Online discovered another court appearance by the Duke in 1906, the year his second son, George, was born.
At Wimborne, yesterday, the Duke of Hamilton obtained a vaccination exemption certificate on the ground that he conscientiously believed vaccination would be prejudicial to his child's health.
But no further reports of court appearances have yet been located.
What influenced the Duke to become an anti-vaccinationist? Quite possibly because of the influence the Duchess, Nina Douglas-Hamilton who was a founder of the Animal Defence and Anti-vivisection Society. Many anti-vaccinationists were also committed anti-vivisectionists, probably owing to the use which was made of calves to cultivate the cowpox lymph used in vaccinations. The Duchess remained committed to animal rights until her death in 1951.
The Vaccination Inquirer and Health Review of August 1907, reported that the Duke was to open a fete being held in aid of the N.S.P.C.C., with a “beautiful baby” class. Perhaps somewhat with tongue in cheek, a suggestion had been made that the committee should have a speciality class for ‘…un-cowpoxed bairns and that the Duchess herself could enter two.
Did the Duke obtain exemption for “the Heir and the spare”? Did he allow his other children to be vaccinated? It is impossible to know with any degree of certainty. What is certain is that the Scottish Anti-Vaccination League considered his membership to be something of a coup, one which would encourage others to follow his lead. It is a pity that the society records are not in an archive, but one can live in hope that somewhere, they are lurking still in a box and might yet be re discovered
 St George Hanover Square Registration District, March Quarter, volume 01A, page 449.
 Poole Registration District September Quarter 1904 Volume 5a, page 243
 Poole Registration District March Quarter 1906 Volume 5a, page 241.
 Stockbridge Registration District December Quarter 1907 Volume 2c, page105.
 Avondale Registration District, November 1909 621/108, page 36
 Avondale Registration District, November 1912 621/88, page 30.
 Avondale Registration District, August 1914 621/74, page 74.
 The Vaccination Inquirer and Health Review, Volume 26, no.388, page 162, November 1904.
 Bellshill Speaker 2 September 1904.
 The Vaccination Inquirer and Health Review, Volume 26, no.311, page 213, February 1905.
 Globe 21 April 1906
 Jon Wynne-Tyson, Nina Mary Benita Douglas Hamilton, Duchess of Hamilton, Oxford Dictionary of National Biography, September 2004.
 The Vaccination Inquirer and Health Review, Volume 29, no.341, page 88, August 1907