Nearly 20 years ago, measles in the United States was all but a distant memory, and the disease was declared eradicated. Beginning around 2012, however, measles began to make a dramatic comeback, with outbreaks across the country and a steadily growing number of cases. In 2019, the Centers for Disease Control and Prevention announced the worst measles outbreak since 1994.
Health experts believe there are a few reasons why the number of people, especially young people, with the measles has increased:
- More international travel has made it possible for people to continually “re-introduce” measles to the US.
- More parents are opting out of vaccinating their children due to concerns over the safety of the measles vaccine, thus increasing their risk of measles infection.
- In rare cases, the measles vaccine may not prove effective in preventing the vaccination’s spread. For example, people who were vaccinated before 1968 did not receive long-term protection against the disease.
How does the vaccine work?
The measles vaccine is a live virus vaccine that contains live but weakened forms of the virus. The mumps and rubella viruses are often included with this vaccine (e.g., the MMR vaccine).
When a person is injected with the MMR vaccine, their body begins making cells known as antibodies to fight the virus. Because the virus in the vaccine is weakened, the antibodies are able to successfully overtake the virus without causing a full-blown measles infection. If a vaccinated person is exposed at a later date to the measles virus, the antibodies have a “memory” from the vaccine that allows them to destroy the virus without infection. This is known as acquired immunity.
Typically, the first dose of the MMR is administered between 12-15 months of age, when a child’s immune system is strong enough to build up sufficient protection against the virus. A second dose is given between the ages of 4-6 years of age.
How effective is the vaccine?
On rare occasions, people who have received two doses of the MMR vaccine still fail to develop antibodies at a high enough level to protect against measles exposure. This concept is known as vaccine failure. According to a report published in the January 2012 edition of Vaccine, anywhere from 2 -10 percent of people immunized with two doses of the vaccine did not have high enough antibody levels to be protective. The journal article ended with a call to develop more effective vaccines to achieve a lower failure rate but still strongly recommended immunization for all children.
While the measles vaccine may not be a perfect vaccine, it has protected many Americans, especially children, against measles. According to Vaccine, measles killed an estimated 777,000 people worldwide in 2000 compared to 160,000 people worldwide in 2010. This decrease is widely attributed to increased vaccination rates. According to the New York Department of Health, those who did not get vaccinated against measles are 22 times more likely to get measles than those who received two doses of the vaccine.
Reviewed by Dr. Sara Connolly, April 2019
- Once eradicated in the US, the last five years have shown that measles will spread quickly when re-introduced into communities with low vaccination rates.
- The measles vaccine is composed of a live, weakened virus that help the receiver build up immunity against the virus.
- Two doses of the MMR vaccine are 97% effective in preventing disease in people with healthy immune systems.
- Vaccines are still considered the best way to protect a person against measles.