Which of the following actions would not typically reduce the presence of vectors?

Vaccination programs primarily focus on preventing diseases in individuals and do not directly address the presence of vectors, which are organisms that spread pathogens, such as mosquitoes and ticks. While vaccinations can reduce the incidence of diseases transmitted by these vectors, they do not eliminate the vectors themselves or their breeding sites.

In contrast, the other measures mentioned directly target vector populations. Eliminating standing water removes potential breeding sites for mosquitoes. Using insect repellent provides a protective barrier against the bites of vectors, thereby reducing the chance of transmission of diseases. Closing off breeding sites further minimizes the habitat available for vectors to reproduce. Thus, while vaccination is essential for public health, it does not specifically reduce the presence of vectors like the other options do.