The first measles vaccine arrived in 1963

The measles vaccine was licensed in the United States in March 1963. It was developed by John Enders and his colleagues at Boston Children's Hospital, building on decades of work to grow the measles virus in laboratory conditions. The original vaccine used a live virus that had been weakened through repeated growth in animal cells—a technique called attenuation.

Before 1963, measles was a routine childhood infection in the U.S. Nearly every child caught it by age 15. The disease killed roughly one or two children per thousand infected, and caused serious complications like pneumonia and brain inflammation in a significant fraction of cases. A vaccine that could prevent this changed the landscape of childhood illness almost immediately.

Key Takeaways

  • The measles vaccine was licensed in the United States in March 1963, developed by John Enders and colleagues at Boston Children's Hospital.
  • The original 1963 vaccine used a live weakened virus and reduced measles cases by over 90 percent within a decade of widespread use.
  • A second vaccine strain, the Moraten strain, became standard in 1968 and is still the basis for the measles vaccine given today.
  • The two-dose schedule (first dose at 12 to 15 months, second dose at 4 to 6 years) was adopted in the 1980s and provides immunity in over 99 percent of vaccinated children.

How the original vaccine worked and why it changed

The 1963 vaccine used a live measles virus that had been weakened so it could replicate in the body but cause only mild or no symptoms. This approach—using a live attenuated virus—triggers a strong immune response because the virus actually grows inside vaccinated people, mimicking natural infection without the danger.

The original strain, called the Edmonston strain after the child from whom the virus was first isolated, worked well but sometimes caused a rash and fever in vaccinated children. In 1968, a modified version called the Moraten strain was licensed. It caused fewer side effects while maintaining the same protection. The Moraten strain became the standard and remains the basis for measles vaccines used worldwide today.

Measles cases dropped sharply after vaccination began

In 1962, the year before the vaccine was licensed, the U.S. reported over 500,000 measles cases. By 1968, that number had fallen to around 23,000—a decline of more than 95 percent in just five years. Deaths from measles fell even more steeply because vaccination prevented not just infection but the severe cases most likely to be fatal.

This rapid decline happened because vaccination rates climbed quickly. By the early 1970s, roughly 85 percent of American children had received at least one dose. The combination of high vaccination rates and the vaccine's effectiveness at preventing infection created what epidemiologists call herd immunity—when enough people are immune, the virus cannot find enough susceptible hosts to spread.

Why a second dose was added decades later

For the first 20 years after the vaccine's introduction, one dose was considered sufficient. However, by the early 1980s, public health officials noticed that a small percentage of vaccinated children—roughly 5 percent—did not develop immunity from a single dose. Some of these children later caught measles, usually with milder symptoms than unvaccinated children but still contagious to others.

In 1989, the CDC recommended a second dose for all children, given at school entry (around age 4 to 6 years). This two-dose schedule catches the roughly 5 percent who did not respond to the first dose and provides a safety margin. With two doses, over 99 percent of vaccinated people develop immunity that lasts a lifetime.

The vaccine's composition has stayed essentially the same

The measles vaccine given today is still a live attenuated virus, still based on the Moraten strain licensed in 1968. The manufacturing process has become more refined—the virus is now grown in chicken egg cells rather than the animal cells used in the 1960s—but the fundamental vaccine has not changed.

In most countries, measles vaccine is given as part of the MMR vaccine, which protects against measles, mumps, and rubella with a single injection. Some countries use MMRV, which adds protection against varicella (chickenpox). The measles component of these combination vaccines is still the same live attenuated virus that Enders and his team developed more than 60 years ago.

What happened to measles after vaccination became widespread

By 2000, measles transmission had stopped in the United States. The last case acquired from someone living in the U.S. was reported in 2011. Cases that occur now are almost always imported by travelers from countries where measles still circulates, or occur in pockets of low vaccination coverage where the virus can spread among unvaccinated people.

Globally, the picture is different. Measles still kills tens of thousands of children each year in countries with lower vaccination coverage. However, vaccination campaigns have reduced global measles deaths by over 70 percent since 2000. The vaccine that arrived in 1963 remains one of the most effective tools for preventing infectious disease.

Frequently Asked Questions

Is the measles vaccine the same now as it was in 1963?

The vaccine is based on the same principle—a live weakened virus—but the strain changed in 1968 to the Moraten strain, which causes fewer side effects. Manufacturing has become more precise, but the core vaccine has remained essentially unchanged for over 50 years.

Why did it take so long to develop a measles vaccine?

Scientists needed to grow the measles virus reliably in the laboratory before they could weaken it for a vaccine. This required developing cell culture techniques that did not exist until the 1950s. Once those tools were available, the vaccine was developed and tested within about a decade.

Can you catch measles from the vaccine itself?

The vaccine virus is too weak to cause measles disease in healthy vaccinated people. Vaccinated people may develop a mild rash or low fever, but this is not measles. The vaccine cannot spread to other people because the virus does not replicate enough to shed from the body.

How long does immunity from the measles vaccine last?

Immunity from two doses of measles vaccine lasts a lifetime in over 99 percent of people. A single dose provides lifelong immunity in roughly 95 percent of vaccinated people. Booster doses are not needed for people who received two doses as children.