Name an example of a viral disease that can be effectively prevented by a vaccine.

Measles is a viral disease that can be effectively prevented by a vaccine, specifically the measles, mumps, and rubella (MMR) vaccine. The vaccine has demonstrated high efficacy in creating immunity against the measles virus, significantly reducing the incidence of disease among vaccinated populations. Measles is highly contagious and can lead to serious complications, making vaccination crucial for controlling its spread.

In contrast, Hepatitis C currently does not have an effective vaccine available. While treatment options exist, prevention relies on public health measures rather than vaccination. Similarly, while there is ongoing research into vaccines for HIV/AIDS, there is currently no effective vaccine available that can provide immunity against the virus. COVID-19, on the other hand, does have effective vaccines available, but it is important to identify that measles represents a classic example of successful vaccination for viral disease prevention, with a long history of vaccine use leading to substantial declines in global cases.