This is the 18113th most frequent Russian word.
холерную
The Russian word "холерную" translates to "cholera-related" in English.
In this sentence, 'холерную' is an adjective modifying the noun 'вакцину', describing the type of vaccine, which is cholera-related.
Этот врач изобрел холерную вакцину.
This doctor invented a cholera vaccine.
Here, 'холерную' serves as an adjective defining 'морфологию', indicating that the morphology pertains to cholera.
Она изучала холерную морфологию в университете.
She studied cholera morphology at the university.
In this example, 'холерной' modifies 'эпидемии', describing the epidemic as related to cholera.