Most of the immunisations you need to fend off nasty diseases are normally given as a child, so as an adult, you'll rarely need to be jabbed in order to stay healthy. One of the most common adult vaccines is the one given for flu, but that's not as important unless you're in one of the groups of people most at risk of complications.
The biggest exception is when you're travelling. There are various infectious diseases around the world that aren't a risk at home, so it's important to be immunised against them if you're going where they're present. Many of these diseases have serious consequences, so check with your doctor if you're not sure what's present where you're heading. Here are some of the nasty diseases still found around the world.
Yellow fever typically lasts about a week, with symptoms similar to a bad case of the flu, complete with nausea and aching muscles. While that in itself would certainly ruin your holiday, the real problem occurs in a percentage of people. In this subset, shortly after the symptoms disappear, they return with added liver and kidney damage.
The disease is spread by a particular type of mosquito, found mostly in parts of Africa and South America.
While rabies can occur anywhere, there are certain places where the risk is particularly high. Spread by animal bites, the majority of rabies cases in humans come from dogs, but there's also a risk from various wild animals. In some places, the disease may not be present in terrestrial animals, but can still be contracted from bat bites.
Asia and Africa are the places where the risk is highest, but rabies is present somewhere on every continent, so check with your doctor to find out if you'll need the vaccine.
Hepatitis is often sexually transmitted, but it can be passed on through other forms of close contact as well. There's a chance you can come into contact with it anywhere in the world, but it's especially prevalent North Africa, South and Central America, and throughout Asia and the Middle East. If you're travelling to any of these places, the vaccine is recommended.
This bacterial infection is mostly characterised by a high fever, often with other flu-like and digestive symptoms. It's found pretty much everywhere but is mostly absent as long as there are good levels of sanitation. Africa, Asia, Europe, the Middle East, and Central and South America are all typhoid hot spots.