Measles is a highly contagious illness caused by a virus. It spreads through the air when an infected person coughs or sneezes, and it can linger in a room for up to two hours after that person has left. Because it spreads so readily, even a small number of cases can grow quickly in a community where many people are not protected.
What measles did before the vaccine
It is easy to forget how dangerous measles was, because the vaccine made it rare. Before the measles vaccine arrived in the United States in 1963, the disease swept through nearly every childhood — an estimated 3 to 4 million cases every year. On average, each year that caused:
- 400 to 500 deaths
- about 48,000 hospitalizations
- roughly 1,000 cases of encephalitis (swelling of the brain), which could leave a child with permanent deafness or lasting intellectual disability
Measles can also damage sight. Globally it remains a leading cause of childhood blindness, usually in children who are not vaccinated and are short on vitamin A.
Why get vaccinated
These numbers fell by more than 99 percent after widespread vaccination.
The protection is not only personal: when most of a community is vaccinated, the virus has nowhere to spread, which shields infants and others who cannot be vaccinated. That is why keeping vaccination rates high matters.
Further reading
The figures on this page are drawn from these authoritative sources:
- World Health Organization — MeaslesGlobal fact sheet: symptoms, spread, complications, and vaccination.
- Stanford Medicine — Understanding measlesAcademic overview, including the U.S. pre-vaccine case and death figures.
- Congressional Research Service — Measles outbreaks & policy (PDF)Nonpartisan federal research summarizing pre-vaccine U.S. cases, hospitalizations, and deaths.
- Illinois Dept. of Public Health — History of measlesA state health department's summary of measles before and after the vaccine.