Does Getting Sick Give You More Immunity Than Getting a Vaccine?

I was having a discussion with a colleague who said that it is a well-documented fact that immunity deriving from getting sick is much stronger than immunity from vaccination. I did some research but couldn’t find anything on the subject. Can you help?
—Luisa

The answer to this question depends slightly on what vaccine and virus you are talking about. But it is true that for many viruses, the immunity from getting sick is greater than the immunity from a single vaccine. This is why, for example, we give kids two measles vaccines as the standard dose, whereas a single infection with measles would provide lifelong protection.

But measles is also a good example of why it’s important to weigh the costs and benefits. Two doses of the measles vaccine provides virtually complete protection against getting measles. The side effects of the vaccine are minimal, and decades of experience has shown it to be safe. Actually getting measles is not a good substitute. It can be very serious, even fatal.

The reason illness is often more potent than vaccination is that when you get sick, your body produces a big response — lots of antibodies, since you’re really ill. With vaccines, we aim to get an adequate response but not to overwhelm your system, which would produce more side effects. So the smaller dose leads to less potency, and this is why we often need multiple doses.

There are some vaccines where the vaccination response is actually better (like HPV), so it doesn’t always work this way, but it does for many vaccines. But, again, the vaccines have the distinct advantage of not involving being sick, or getting others sick.