A new study of measles and pertussis epidemics in the United States suggests that refusal or reluctance to vaccinate children against the diseases may have contributed to recent outbreaks in this country. The research, published March 15 in the Journal of the American Medical Association (JAMA), found that the number of nonmedical vaccine exemptions have increased steadily over the last 20 years.
“When vaccine refusal rates are high, the rates of measles and pertussis are higher,” study researcher Varun Phadke, MD, a fellow in infectious diseases at Emory University in Atlanta, told HealthDay.
Measles and pertussis – also known as whooping cough – are vaccine-preventable diseases. Both were officially considered eradicated in the U.S, in 2000, when rates for the diseases were at the lowest since 1977. Recent outbreaks of measles and pertussis, however, have focused attention the association between vaccine refusal and the rising number of outbreaks.
And both are serious diseases to contend with. The Centers for Disease Control and Prevention (CDC) reports that children under the age or 5 and adults older than 20 are most prone to serious measles complications, including inner ear infections that can cause deafness, pneumonia, and brain swelling that can lead to convulsions. Pertussis is especially dangerous for babies younger than a year.
For the new study, researchers led by senior author Saad B. Omer, PhD, a pediatric and epidemiology researcher at Emory University, analyzed 18 published studies outlining 1,416 measles cases. The research team also reviewed 32 reports of pertussis outbreaks involving 10,609 patients.
The measles cases included patients ranging in age from 2 weeks to 84 years. Findings showed that 57 percent had no history of measles vaccination. Of the 970 measles cases that had detailed data, 574 cases were unvaccinated despite being vaccine-eligible. Among this group, 71 percent had nonmedical exemptions – religious or philosophical reasons as opposed to medical reasons such as allergies to vaccine ingredients, cancer treatment, or compromised immune systems for refusing vaccination.
Pertussis cases involved patients who ranged in age from 10 days to 87 years. Among this group, 24 percent to 45 percent of the people in the five largest statewide epidemics since 1977 were unvaccinated or only partially up-to-date on their vaccines. The researchers also found that in eight of 12 pertussis outbreaks for which data vaccination data was available, as many as 93 percent of unvaccinated patients intentionally avoided immunization.
However, several pertussis outbreaks also occurred among highly vaccinated populations. The research team suggested these epidemics were the result of decreased immunity among the group.
Officials at the CDC noted that large outbreaks such as these generally happen in clusters. “While coverage rates are high nationally, locally there may be clusters of under vaccinated or unvaccinated children that put those children, their schools and communities at risk for outbreaks,” the CDC said in an email to Healthline.
And there’s the rub. While parents may argue it is their right to decide whether or not to vaccinate their children, health experts counter with the need to overcome the risks to the child and the general population. Vaccinations, they say, are the safest and most effective way to protect against many diseases.
In an accompanying editorial, Matthew Davis, MD, a pediatrics researcher and deputy director of the Institute for Healthcare Policy and Innovation at the University of Michigan in Ann Arbor, said of the study, “What this latest comprehensive review illustrates is that individuals who refuse vaccines not only put themselves at risk for the disease, it turns out they also put others at risk too – even people who have been vaccinated before, but whose protection … may not be as strong as it used to be.”