Faced with the highest number of measles cases in a dozen years, officials at the Centers for Disease Control and Prevention are warning parents to vaccinate their children to ward off further outbreaks.
From January through July, 131 measles cases have been identified in 15 states and the District of Columbia - the most since 1996, the CDC announced yesterday. About half of the cases involve children whose parents refused to vaccinate them for religious or philosophical reasons.
No cases have been detected in Maryland. No deaths have been reported.
Nevertheless, local vaccine experts joined CDC officials yesterday in alerting parents that measles is still a threat and that vaccinations are vital to stopping the spread of the highly contagious disease.
"It is important we maintain high disease vaccination," said Dr. Neal Halsey, director of the Institute for Vaccine Safety at the Johns Hopkins Bloomberg School of Public Health. "Getting vaccinated is the safest thing we can do for children."
As a warning, CDC officials are using statistics from countries such as Switzerland, Italy and the United Kingdom that are reporting measles outbreaks caused by failure to vaccinate. Of the 131 U.S. cases this year, 17 were people who either traveled abroad and returned with the disease or were foreign visitors to the United States.
"At the national level, I am concerned about our situation," said Dr. Anne Schuchat, director of the National Center for Immunization and Respiratory Diseases. "Every year, the U.S. experiences importation of measles. What is different this year is once it is imported, we are seeing it spread to more people, and most of that spread is to people under 20."
Since the availability of the measles vaccine in the 1960s, the United States has experienced occasional outbreaks. But in recent years, the number of cases has been held relatively low, with 55 cases reported in 2006 and 66 cases in 2005. Public health experts attribute those low figures to widespread vaccinations.
Although the rates of vaccine coverage remain high in the United States, countries with similar vaccination rates, such as the United Kingdom and Israel, are struggling with outbreaks.
"This highlights that even with extremely high vaccine levels, we could have sizable pockets of people contract measles," said Dr. Jane Seward, deputy director of the CDC's viral diseases division. "Similar to what's happening in Israel, it could result in much higher outbreaks than we have now."
The symptoms of measles include rash, high fever, cough, runny nose and red, watery eyes. The disease can lead to pneumonia, encephalitis - a brain inflammation that causes neurological defects - and death.
All states require school-age children to be vaccinated against measles, which involves two doses, the first typically given between 12 and 15 months and the second between 4 and 6 years. States offer exemptions for children with certain medical conditions that result in a weakened immune system. And most states allow exemptions for religious and philosophical reasons.
Halsey, the Hopkins vaccine expert, thinks parents are asking for more exemptions lately without understanding the dangers.
"One of the reasons that some parents have withheld measles vaccines is they believe that the risk is very low" of contracting measles, he said. "That is, unfortunately, a false belief."
Halsey also blamed news media reports questioning the safety of the vaccine and a possible connection to autism for fueling doubts. Both Halsey and the CDC say studies have shown no credible link between the vaccine and autism. "I think that publicity about concerns about the safety of vaccines has contributed to parents delaying or deferring the vaccine for their children," he said. "Unfortunately, parents are not considering the risks of the disease."
In addition, Halsey warned of the importance of both doses of the vaccine. One dose provides 95 percent protection. Of the 131 people who contracted measles this year, 11 had received some level of vaccination.