The text of the first document presented in this article to illustrate the issue of health literacy, a publication from 1768, stands out for resorting to different forms of knowledge organization to convince the authorities of the need for mass use of the inoculation process against smallpox, a disease that affected Europe and Brazil. It is a letter from the English doctor, dr. Gualter Wade, who, living in Portugal, was responding to a query about what would be new and worthy of imitation in the fight against smallpox. In addition to the representativeness of the language used in the document, a sample of the doctor's effort to prove the safety of inoculation for the elimination of bladders, the topic comes in handy with the current debates, in which the efficacy of vaccines against infectious diseases is still being discussed. The second document, from 1775, handwritten by the captain-general of the captaincy of São Paulo, Martim Lopes Lobo de Saldanha, and addressed to the then secretary of State for the Navy and Overseas, Martinho de Melo e Castro, is a counterpoint to the approach to the sanitary issue, in relation to the 1768 document, since homemade and ineffective measures continued to be used in the colony.