Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:In addition, these vaccines may also prevent or reduce transmission of pathogens by reducing tick populations and/or affecting tick vector capacity (de la Fuente et al. 1998, 2007a; Rodríguez Valle et al. 2004).
Category: