The re-emergence of measles presents a compelling case study for why immunizations are so important, Dr. Vandana Madhavan told an audience of mostly health care professionals in a public presentation, part of the Martha’s Vineyard Hospital’s Health Fair on Saturday.
A nationwide inoculation campaign with the highly effective measles/mumps/rubella (MMR) vaccine made measles cases rare in the U.S., and the disease was considered eradicated in 2000, Dr. Madhavan said.
But measles is not a disease of the past. Last week, the Centers for Disease Control (CDC) reported 173 cases in 17 states and the District of Columbia, Dr. Madhavan said. Most of the cases were linked to a December 2014 outbreak in Disneyland, but there also have been three unrelated outbreaks since that, in Illinois, Washington, and Nevada.
Dr. Madhavan, a pediatric infectious disease specialist at the Massachusetts General Hospital for Children, said the spike in measles corresponds with a growing percentage of nonimmunized children. Unfortunately, the decrease in immunizations has impacted “herd immunity” in the general population, she explained.
That term refers to a form of indirect immunity that occurs when a large percentage of the population is immune to an infectious disease, which provides a measure of protection for those who aren’t immune. A greater number of immune people lessens the chance for a nonimmune person to come into contact with someone infected with a disease.
In recent years, some parents have chosen to delay or opt out of recommended vaccine schedules for their children, which puts others in their community at risk by decreasing herd immunity.
A pocket of concern
From 1994 to 2013, the national percentage of MMR vaccinations overall was great, Dr. Madhavan said, and in Massachusetts, overall vaccination rates are excellent. Massachusetts law requires vaccinations against 14 communicable diseases, including the MMR vaccine, as a condition of enrollment in public schools. In addition to medical exemptions, Massachusetts allows exemptions on religious grounds.
“We’re generally almost always first in the country for our state’s overall rate; however, there are pockets of nonimmunized children,” she added.
Dr. Madhavan said the most recent statewide immunization survey, organized by school, city, and county, shows an enormous amount of variability, with Martha’s Vineyard’s rate of nonimmunized children among the highest.
“There is a school exemption rate of over 20 percent here on the Vineyard, with an MMR vaccination rate for kindergartners at 77 percent, which is far below what we need for herd immunity,” Dr. Madhavan said.
The results of the state vaccination survey also reveal that families who choose not to immunize their children tend to cluster geographically and seek out the same pediatricians and schools, particularly private schools that are known to be more accepting of vaccine exemptions.
“Those nonimmunized pockets are what concerns me and those concerned with the potential resurgence of certain infections,” she said.
Adisproven research paper written by former British surgeon and researcher Andrew Wakefield that linked vaccinations to autism has continued to fuel many parents’ fears since its publication in the medical journal Lancet in 1998.
Dr. Madhavan said that Mr. Wakefield’s paper was retracted in 2010 after his claims were proven to be based on fraudulent research and altered facts about the 12 children in the study. He moved to the U.S. after being stripped of the right to practice medicine in the United Kingdom.
Despite many subsequent studies based on medical evidence showing there is no link between vaccinations and autism, celebrity supporters such as actress Jenny McCarthy continued to perpetuate Mr. Wakefield’s findings, and incidences of measles have increased since his paper was published.
How bad can it be?
Although some people think of measles as a fairly benign childhood disease, Dr. Madhavan ran down a sobering list of possible complications that include ear infections, pneumonia, and croup, as well as acute encephalitis, which may occur in one in every 1,000 cases.
As a poignant example, Dr. Madhavan read an excerpt from an essay about the danger of measles by children’s author Roald Dahl, whose 7-year-old daughter Olivia died of measles-related encephalitis in 1962.
Mr. Dahl urged all parents to have their children immunized, which he said he was unable to do for Olivia because a safe, reliable measles vaccine was not available when she was born.
“In my opinion, parents who now refuse to have their children immunized are putting the lives of those children at risk,” Mr. Dahl wrote. “It really is almost a crime to allow your child to go unimmunized.”
Dr. Madhavan said the effects of measles also can linger and have long-term devastating consequences. Survivors may suffer subacute sclerosing panencephalitis, a fatal disease of the central nervous system, seven to 10 years after acute measles.
There is only one type of measles. Its incubation period could potentially be as long as three weeks, Dr. Madhavan said. Symptoms include fever, cough, runny nose, red eyes, mouth lesions, and a rash. Measles is one of the most highly contagious diseases. A child exposed to measles may be transmitting the virus to other people while still mildly ill. Patients are contagious four days before a rash appears, and up to four days after.
The virus is spread mainly by direct contact with airborne respiratory droplets, created when someone who is infected coughs or sneezes, that can remain infectious for up to two hours. Dr. Madhavan noted that there is much less fear about measles than other diseases, even though the transmission risk is so much greater and the potential for morbidity and mortality can still be so high.
“People are so worried about Ebola; Ebola has a much higher death rate, but measles is one of the most easily transmittable infections out there,” Dr. Madhavan said. “Someone with measles could be in this room, the health fair could be finished, and someone unimmunized that came in here could catch measles, without being in the same physical proximity as that person at all.”
Rates and trends
According to measles statistics from 1944 to 2007, the annual number of cases in the U.S. peaked in the late 1950s at nearly 800,000, and the number of deaths at 2,400.
There was a marked decrease in cases with the introduction of a vaccine in the 1960s. In the late 1980s, however, the number of cases spiked again, leading health professionals to recommend a second dose of the MMR vaccine. The MMR vaccine is now administered to children in 2 doses, one at 12 to 15 months and a second at 4 to 6 years.
At her presentation’s conclusion Dr. Madhavan took a few questions from the dozen or so people, most of them health professionals, in the audience. No parents present asked about or commented on the antivaccine viewpoint.