He served in the Spanish military and engineered a successful vaccination program against smallpox in 1804 and 1805.
[4] In Origins of New Mexico Families, Fray Angélico Chávez states extant orders given to Larrañaga to vaccinate the area until 1809.
[9] In Tocante a monumentos de españoles, author Jerry Padilla says that Larrañaga should be honored for his efforts of vaccinating so many.
[10] On page 106 of Land Claims in New Mexico, Congressional Edition, Volume 967, Larrañaga signs as secretary of the Corporation (Capital) of Santa Fé.
Larrañaga is mentioned as deserving a promotion due to his extensive knowledge of medicine.