Oh hi, I just answred your other similar question! Here’s what I said:
That’s quite tricky, as there are many infectious diseases that spread quickly through a population. For example measles – if people aren’t vaccinated 90% of those will catch it if they come into conatct with it. And Malaria is a huge probem – it’s spread by mosquito bites in tropical regions and kills millions of people every year. Then there are things like Influenza (the ‘flu’ or the common cold, which are highly contagious because they are spread by coughs and sneezes which are difficult to contain!
Right now, there are trials testing vaccines as treatments for cancer but there aren’t any available – but hopefully there will be if the trials are a success. Some cancers can be caused (or at least helped along) by viral infections, such as cervical cancer caused by the human papillomavirus (HPV), or liver cancer caused by hepatitis virus. There are currently vaccines against HPV and hepatitis which can prevent those cancers. One problem is that cancer is not one single disease, there are many different types which act in different ways in different parts of the body, but scientists are working on it! There’s good information on the Cancer Research UK website if you want to read further.