SAN DIEGO, Oct. 9 (UPI) -- The United States may be in for more and larger measles outbreaks as national vaccination rates slip below those needed for herd immunity, according to new research at Emory University.
Researchers in the new study, presented at the annual conference of the Infectious Diseases Society of America, found that one in eight children -- nearly 9 million -- is at risk of contracting measles because of gaps in vaccination.
The measles, mumps and rubella, or MMR, vaccine is given to children in two doses, one between the ages of 12 and 15 months and the second when they are between four and six years old. Some young children are not vaccinated for medical reasons or have not completed the two-shot cycle because of their age, but the number of unvaccinated children has increased in recent years because parents are questioning vaccines' safety.
"Right now we have a little bit of a buffer," Robert Bednarczyk an assistant professor at Emory University, told the Boston Globe. "But it's just that: a little bit of a buffer. If we do start to see immunization levels dip down a little bit and we see those dips sustained, we could start to lose that overall population level immunity. And if measles get introduced, we may start seeing larger and more severe outbreaks."
Researchers analyzed national vaccination data collected as part of the annual National Immunization Survey - Teen. They found that between 92 and 94 percent of children are immune to measles.
While most children still receive the vaccine, 12.5 percent of all children have not received it, 24.7 percent of children age 3 or younger have not been fully protected against measles, and 4.6 percent of 17-year-olds had not received any doses of MMR vaccine.
At 92 to 94 percent, national vaccination rates are just enough to maintain herd immunity to prevent the spread of the disease should a small outbreak occur. The researchers warn, however, that should that rate drop to 98 percent of its current status, one in seven children will vulnerable to contracting measles.
"We know some parents have concerns about vaccines and may want to avoid or delay vaccination, or follow an alternative schedule than the one recommended because they're concerned about the safety of the vaccine," Bednarczyk said in a press release. "In fact, the vaccine is very safe, while not vaccinating is highly risky, leaving their children -- and others -- vulnerable to a serious illness that can cause a large number of complications. Currently, these children are protected because of the high vaccine coverage of the population, but that will change if we begin having more outbreaks and the percentage of children vaccinated declines."
