Live Vaccines: How They Work and How They're Made

Of course you know that vaccinations are super important to your child’s health, but how much do you really know about what goes into them and how they work? The science behind them is fascinating, but at the same time, vaccination is one of the most natural ways to prevent infectious diseases. 

Types of vaccines

Some vaccines are made from a killed version of the virus or bacteria that they’re meant to protect us from. Others are made from only a specific piece of a germ or from a toxin that the germ produces. The last type is a “live” vaccine, which actually contains the live (but weakened) virus or bacteria. While they all work in about the same way, live vaccines offer the best protection and only require one or two doses in a lifetime, rather than boosters every few years.

How are live vaccines made?

The main active ingredient in a live vaccine is the antigen, which is the weakened germ. Some vaccines also contain adjuvants, which are substances that, when added, help your immune system to be more effective at responding to the germ.

The inactive ingredients in a vaccine are there to keep the active ingredients safe and effective during storage or transport. These might include preservatives to keep the vaccine fresh and free from outside germs, and stabilizers to protect it from the effects of temperature changes.

How do they work?

Vaccines are based on the natural response of our bodies’ immune systems when we get sick—which is to fight the infection and kill the invading germs. Some germs are relatively easy to fight off; for example, healthy people typically don’t die from a cold virus or pink eye. Some germs, however, are nastier and can cause dangerous, even fatal diseases before our bodies have time to mount a defense.

When a child gets a vaccine, their immune system gets a sneak peek at one of those especially nasty germs as it fights the weakened form. Then, if that child ever comes into contact with the “real” germ, their body recognizes the threat right away and fights it off without ever becoming seriously ill. In short, vaccines teach your child’s body to defend itself and stay healthy—and a healthy child is all a parent really wishes for.