Measles vaccination rates fell to the lowest level in more than a decade during the COVID-19 pandemic, complicating efforts to prevent outbreaks, according to a new report from the U.S. Centers for Disease Control and Prevention (CDC).
Globally, a record high of nearly 40 million children missed a measles vaccine dose last year, including 25 million kids who didn’t get the first of two recommended doses, and an additional 14.7 million who missed their second dose, according to the report, which was issued jointly with the World Health Organization (WHO) November 23.
“The record number of children under-immunized and susceptible to measles shows the profound damage immunization systems have sustained during the COVID-19 pandemic,” said the CDC's director, Rochelle Walensky, MD, MPH, in the report.
At least 95 percent of the population needs to be fully vaccinated against measles in order to achieve and maintain what’s known as herd immunity, when enough people are inoculated to effectively eliminate the spread of disease.
In 2021, only 71 percent of children worldwide were fully vaccinated, meaning they had received both doses of the measles vaccine, according to the report. This is the lowest global measles vaccination rate since 2008.
Because measles is highly contagious, slight dips in vaccination rates can lead to a large spike in cases. A study published April 16, 2019, in the Annals of Internal Medicine found that a 5 percent in measles vaccination rates could triple the number of cases. As of 2016, only about 91 percent of U.S. children had received at least one dose of the measles vaccine — too few to create herd immunity.
With suboptimal vaccination rates, no region of the world has achieved and sustained the elimination of measles since the vaccine became available more than a half century ago, according to WHO. And since 2016, 10 countries that had previously eliminated the disease have experienced outbreaks.
Measles was eliminated in the United States in 2000. But there were almost 1,300 cases in 31 states in 2019 — the highest number recorded since 1992, the CDC reported. All the measles outbreaks that year were linked to travel-related cases that affected people who weren’t fully vaccinated, according to the CDC. International travel as well as travel within the United States have helped spread the virus.
Several large measles outbreaks have occurred in the United States in recent years, including a multistate outbreak that originated at Disneyland in California and resulted in 147 cases, and an outbreak within several close-knit Orthodox Jewish communities in New York City and New York state that resulted in more than 280 cases.
Measles is highly contagious. Nine in 10 people who aren’t fully vaccinated become infected when they’re exposed to the virus, according to the CDC.
Infected individuals can spread the virus for several days before and after telltale rashes appear that are a hallmark of these infections. The virus can also survive up to two hours on surfaces, and people can easily become infected by touching these contaminated surfaces then rubbing their eyes, nose, or mouth. People can also become infected when they inhale droplets after somebody with measles coughs or sneezes.
Infections often begin with a fever, followed by a cough, runny nose, or pink eye. Rashes on the face and neck appear next, then spread to the rest of the body. In the most serious cases, people can develop pneumonia and encephalitis (inflammation in the brain), which can be fatal.