Smallpox was rife throughout Siam and returned every year, affecting much of the population – Dr Bradley himself lost a daughter to it. He worked on a vaccination and documented his efforts in his treatise of 1844.
The complete “Treatise on Vaccination” has been transcribed from scans of the original documents and published on this site.
To give some context to this document, inoculation had been practised in Siam before Bradley's arrival with the Chinese, Indians and Europeans having their own methods for it. Terwiel  gives a detailed account of the history of these practises and a balanced account of Bradley's role in the vaccination campaigns from the 1830s and into the mid-1840s.
An English translation of the treatise by Pearson  was printed in 2016 and available online.
- Terwiel, B.J. Acceptance and Rejection: The First Inoculation and Vaccination Campaigns in Thailand (PDF) Journal of the Siam Society, Vol.76, 1988
- Bradley, D.B. translated Pearson, Q. Treatise on Smallpox Vaccination (PDF) Journal of the Siam Society, Vol.104, 2016