Herd Immunity Can Slow — or Even Halt — a Disease
Immunity occurs when a person’s body has produced antibodies against a disease, protecting them from developing it, according to The Centers for Disease Control and Prevention (CDC). This can occur after a person has recovered from a disease or received a vaccine for it.
When enough people in a given population have immunity, more than just those people are protected. This is what’s known as herd immunity, also called community immunity.
If most people can’t get sick from a given germ, it’s not as easy for the germ to pass from person to person. Even people who aren’t immune to a disease — because they haven’t been vaccinated or had exposure to it — are therefore less likely to catch it.
Herd immunity can protect the vulnerable people in a population who may not be able to get vaccinated or might be at high risk for complications. This usually includes older adults, newborns and those with underlying health conditions. Herd immunity also reduces the risk for new outbreaks because the harmful infection may be stopped before it can spread widely.
The Power of the Herd
Herd immunity has dramatically reduced the risk for many diseases in the United States and worldwide — and has nearly wiped out some altogether. For example:
Now that many children have received pneumococcal vaccines, fewer older adults have been hospitalized for pneumococcal infections, which can strike the ears, lungs, brain and blood, the U.S. Department of Health and Human Services notes.
Smallpox has been wiped out altogether, thanks to widespread vaccination and community immunity. Now children don’t even have to get shots for it anymore, the CDC explains.
When about 95% of a population is vaccinated against measles, most people are protected, according to the World Health Organization (WHO).
