According to the World Health Organization, measles has been officially eradicated in the Americas — that's all countries in North, Central and South America, from Canada to Chile. That makes the Americas the first region in the world without any endemic cases of what was once considered one of the world's most infectious diseases.

Prior to the introduction of the measles vaccine in 1963, hundreds of thousands of people in the United States contracted the disease every year. In fact, a 1954 scientific review of measles in the U.S. published in the American Journal of Medical Sciences concluded that contracting measles was "as inevitable as death and taxes."

Graph showing measles infections in the U.S. over time Measles cases reported in the U.S. before and after the introduction of the measles vaccine. (Photo: Wikimedia Commons)

But all of that drastically changed with the development of the measles vaccine. Thanks to herd immunity — which means that at least 90 to 95 percent of the population is vaccinated — there has not been an endemic case of the disease in the Americas since 2002 in Venezuela. The U.S. has been declared measles-free since 2000.

But wait, weren't there just cases of measles reported in California a few years ago? Even though the disease has been eradicated from an area, it doesn't mean there are no reported cases; it means that those infections didn't originate in that area.

In the U.S., there are roughly 54 cases of measles diagnosed every year, but they all originate in other countries and are brought into the U.S. according to the Centers for Disease Control and Prevention. If a case is imported near an area where there are lower levels of herd immunity, the disease can still spread in local populations. That's what happened during the measles outbreak that originated in Disneyland in 2014.

That's why herd immunity and vaccinations are so important, even now. There are segments of the population that cannot be vaccinated, such as newborn babies and young children with autoimmune diseases or those who are undergoing chemotherapy. For these children, contracting measles would be a death sentence. But they are protected when the rest of the population gets vaccinated and keeps the disease at bay.

Considering that measles is still responsible for about 314 deaths every day around the world, it's important that we all continue to stay educated — and protected — until the whole world can be declared measles-free.