Measles: Why Vaccinate?

Sonja Koukel, PhD
Community & Environmental Health Specialist

Measles (Rubeola) is a serious respiratory disease that occurs in the lungs and breathing tubes. It is spread from person to person through the air when an infected person coughs or sneezes. Droplets can remain suspended in the air for up to two hours.

In the entire year of 2014, there were 23 reported outbreaks of measles in the United States. In 2015, there were 176 reported outbreaks in just 3 months (January 1 to March 13)! The Centers for Disease Control and Prevention (CDC) shows 465 individual cases of measles confirmed in 19 states since January 1, 2019. What is known about this outbreak:

·       The majority of people who got measles were unvaccinated.

·       Measles is still common in many parts of the world including some countries in Europe, Asia, the Pacific, and Africa.

·       Travelers with measles continue to bring the disease into the U.S.

·       Measles can spread when it reaches a community in the U.S. where groups of people are unvaccinated.

Prior to 1963, nearly everyone in the U.S. became infected before the age of 15. There were an estimated 3-4 million cases of measles each year in the U.S. and an average of 450 measles-associated deaths reported annually (1953-1963).

A measles vaccine was licensed in 1963. In the years following, the number of measles cases dropped dramatically. By 1981, the number of reported measles cases was 80% less compared with the previous year. In 2000, measles was declared eliminated from the U.S.

Today, the measles vaccine is usually combined with mumps and rubella - called the MMR shot. This vaccine is the best way to protect against measles.

What are the advantages of having everyone vaccinated?
 
Herd immunity is the concept behind mass vaccinations. Vaccinated people act as a barrier and reduce the risk of infection for people who cannot be immunized, such as the very young or those with compromised immune systems. For instance, health experts recommend first vaccines for children between 12 to 15 months of age.

Following are graphics used to demonstrate how herd immunity protects in a hypothetical measles outbreak (Corum et.al., 2015).

In a measles outbreak where nobody has immunity, one infected person might infect 12-18 people. Each of those infected people might each infect another 12-18 people. At this rate, a small outbreak quickly grows out of control.

Every vaccinated person (represented with green) reduces the potential sources of infection. Thereby, reducing the risk to unvaccinated people. This reduction in risk is sometimes calls the herd effect (Fig. 2). The presence of vaccinated people helps slow the spread of the disease (Fig. 3).

For an outbreak to end quickly, each infected person must infect, on average, fewer than one other person. In this example, at least 17 of every 18 people (more than 94%) would need immunity. This threshold is sometimes called the herd immunity threshold. To maintain this threshold within a community over time, children need to be vaccinated at a high rate. 

For more information on childhood vaccines and the measles shot, visit the Centers for Disease Control and Prevention website (www.cdc.gov). Talk to your primary care provider for a vaccination schedule.