Measles Anywhere is a Result of Measles Everywhere
Will we ever stop seeing cases of measles?
Last week, officials confirmed the first case of measles in Michigan this year. That may not sound significant. It’s only one case in one state, but it’s actually one of 21 cases of measles reported across 7 different states so far this year.
Last week we also heard the World Health Organization warn of measles outbreaks across Europe. This image, published in an article from The Sun in the UK, illustrates how widespread the outbreaks have been. There are currently 14 countries seeing endemic transmission of measles, to include such countries as France, Germany, Italy, Poland, Romania, Switzerland and the Ukraine. Maybe not the countries you were expecting. And maybe some countries you plan to visit.
Although measles was declared eliminated in the U.S. in 2000, and even eliminated from all of the Americas in 2016, measles still kills an estimated 115,000 children per year all across the globe – that’s 314 measles related child deaths each day. Clearly, measles remains a signifiant global health concern.
And it’s not just measles deaths we worry about. Measles can be a serious illness requiring hospitalization. As many as 1 out of every 20 children with measles gets pneumonia, and about 1 child in every 1,000 who get measles will develop encephalitis – a swelling of the brain that can lead to convulsions, and can leave the child deaf or intellectually disabled. For every 1,000 children who get measles, one or two will die from it.
When we consider the impact of measles worldwide, we begin to understand why every case is relevant and in someway related, and here’s why:
Measles is a highly contagious airborne disease.
When one person has measles, 90 percent of the people they come into close contact with will become infected, if they are not already immune. The virus can linger in the air for up to two hours after an infected person has coughed or sneezed. If other people breathe the contaminated air or touch the infected surface, then touch their eyes, noses, or mouths, they can become infected. This means you don’t even have to have contact with the contagious person to become infected. That is why one a case of measles can easily be spread to others.
Disease elimination is not the same as disease eradication.
Measles elimination is defined as the absence of continuous disease transmission for 12 months or more in a specific geographic area. Measles is no longer endemic in the United States, but that doesn’t mean we don’t still see measles cases. The cases we see here begin with transmission elsewhere. Sometimes cases originate with U.S. citizens who unknowingly contract measles while traveling abroad and then became sick and spread the virus upon returning home. Other times, travelers from other countries arrive in the U.S. while contagious. In both instances, these individuals can spread measles to anyone they come in contact with who isn’t already immune. In recent years, this has caused several widespread outbreaks of measles in the U.S.
There are still many people in this world who are not vaccinated against measles.
It’s estimated that in 2010 about 85% of the global population has received at least one dose of measles vaccine. While that may sound good, it’s still not good enough to stop the spread of measles. Because measles is extremely contagious, the immunity threshold – which is the percentage of individuals who need immunity in order to prevent a disease from spreading – is as high as 95%. Sadly, as of 2014, only about 63% of countries have an immunization rate that is above 90% and even 90% isn’t good enough.
In the U.S., we are fortunate that there is a high percentage of people who have received their vaccines and have immunity to measles. And yet, even in this highly vaccinated population, there are a still a few groups that remain at risk and quite a few cases each year.
- The un-vaccinated; this includes anyone who is not yet old enough to be vaccinated or who willingly refuses to be vaccinated.
- The under-vaccinated; defined as those who’ve only had one of the two recommended doses of measles vaccine.
- Those who were vaccinated but didn’t confer immunity.
If you’ve had a measles vaccine, the chances that you will get measles is extremely low. But there are no guarantees. Between 2% and 5% of people do not develop immunity after the first dose of measles vaccine. Such vaccine failure can occur for a variety of reasons and is why a second dose of vaccine is suggested. This second dose allows people who didn’t respond properly to the first dose to possibly respond to the second dose, and after both doses are administered, it’s believed that vaccine efficacy is as high 98-99 percent. While measles vaccine remains one of our most effective vaccines, it’s still not perfect and therefore a very small chance of infection remains.
Additionally, it is not uncommon for people to be unknowingly under-vaccinated. They may have received an MMR vaccine before two doses were recommended or they just never got around to getting that second dose. For anyone who is uncertain whether they had two doses, they should consult their healthcare provider, especially if they live in an area that is experiencing a measles outbreak, or are planning to travel to a country where measles is endemic.
Most people who are exposed to measles here in the U.S. will probably never realize it because their vaccine induced immunity will keep them from getting sick. However, the disease remains a significant risk to those who willingly refuse the measles vaccine, or who are too young to have received it.
The CDC recommends that the first ose of MMR vaccine – which is the vaccine that protects against measles, mumps and rubella – be administered to children between the ages of 12-15 months.
The reason we usually don’t administer the vaccine until babies are more than 12 months old is because there is evidence that the baby still has some passive immunity from the mom which can actually prevent the baby from mounting a robust immune response to the vaccine. Once the baby is 6 months old that immune response begins to wane, and by 12 months it is believed that children will receive optimal immunity from the vaccine. However, if a child lives or is traveling to an area that has a known measles outbreak, it is advisable for that child to get an MMR vaccine prior to 12 month of age. Since they still may not confer the most immunity at a younger age, those babies will then need to get another MMR vaccine when we can be more certain that the passive immunity from the mother is gone after 12 months of age.
As long as measles remains endemic in so many parts of the world, it can spread to any country, including those that have eliminated the disease. And as long as the disease continues to spread, then there continues to be work to do to protect people from this dangerous, yet preventable disease.