As the US faces its largest outbreak of measles in 15 years - affecting 214 children so far – new research suggests too many unvaccinated U.S. children could be the reason. Experts speculate that unfounded fears regarding safety of the measles-mumps-rubella (MMR) vaccine leading to many children bring missed out could have led to this situation.
Several measles-related studies were unveiled at the annual IDSA annual meeting, currently being held in Boston. In the first report, U.S. Centers for Disease Control and Prevention (CDC) researchers chronicled the nation's ongoing outbreaks in 2011. Most of those sickened were not vaccinated against the disease, CDC researchers said. Before the vaccine became available in the 1960s, some three to four million people contracted measles every year. Of those, 48,000 were hospitalized, 1,000 were permanently disabled and about 500 died, the CDC said. Unfortunately, “we have experienced an increased incidence of measles this year,” said Huong McLean, lead researcher and CDC epidemiologist. “Typically we see 60 to 70 cases a year, this year we have 214 as of Oct. 14.” Throughout the United States, 68 of the patients have been hospitalized, 12 with pneumonia. Among those people infected, 86 percent were unvaccinated or their vaccination status was unknown. Thirteen percent were under one year old - too young for vaccination. Most of these cases occurred among people who traveled overseas to Western Europe, Africa or Asia, where vaccination rates are lower, and the disease is an ongoing problem, the researchers note.
Dr. Andrew Pavia, professor of pediatrics at the University of Utah and spokesman for the Infectious Diseases Society of America (IDSA), said, “The good news is that we are seeing introductions of measles that are being contained as small outbreaks.” Pavia credits containment to high levels of vaccination and rapid response by public health officials. However, if an outbreak occurred in a “really susceptible population the outcome could be very different,” he said. “What would happen in an area with a lot of vaccine refusers? Then you might see a much larger outbreak,” he said.
McLean said that the vaccination coverage in the United states remains relatively high, about 90 percent. “However, measles is very contagious and can spread quickly in communities where people aren't vaccinated,” she said. “The vaccine is very safe and effective in preventing the disease,” McLean said.
“Health care providers together with public health and community leaders must address growing vaccine hesitancy to ensure high immunization rates in all communities,” Pam Gahr, a senior health department epidemiologist, said in an IDSA news release. Not only is measles highly contagious, it's also expensive to contain its spread, according another meeting presentation.
Another Thursday presentation centered on a large measles outbreak in Quebec, Canada: the largest since 1989, with 757 cases as of October 5. That outbreak started with 18 people who traveled abroad, most to Europe. Among those infected, 505 had not been vaccinated or their vaccination status was not known, and 70 had received only one doses of the vaccine, according to the report.
“This outbreak is being fed largely on unvaccinated or undervaccinated people, but we were concerned that a significant number had received the recommended two doses of MMR vaccine,” Philippe Belanger, an epidemiologist at Ministere de la Sant et des Services Sociaux du Quebec, Montreal, said in the releases. Pavia said public health officials should be on the outlook for measles and the high level of vaccination needs to be maintained.
“The ongoing fear of the measles vaccine and the myths about measles vaccine and autism just won't go away - and put us at continuous risk,” Pavia said. One such myth, according to most experts, is that the shot might cause autism in children. Pavia stressed that when parents decide against vaccinating their child, their action may affect other kids, as well. “Your child might get measles and do well. But if you are the one who brings measles back into the community and your child infects someone else in the classroom who can't be vaccinated because of being immunocompromised, you might be responsible for the death of another child or an infant who can't be vaccinated,” he said.
“While this still ongoing outbreak feeds largely on unvaccinated individuals, the high proportion of cases who received two doses raises concerns on vaccine effectiveness,” Philippe Belanger said adding, “However, the take-home message is still to get vaccinated.”
Two mass campaigns were implemented in Quebec in 1996. The goal of the first was to administer a second dose of measles vaccine to children aged 18 months to 16 years, and the goal of the second was to introduce a two-dose measles vaccine schedule in young children (at 12 and 18 months). The first initiative resulted in an 89% coverage rate for the second dose. Despite these efforts, Belanger said that Quebec is experiencing the largest measles outbreak reported in the Americas since 2000.
Between Jan. 1 and Aug. 3, 2011, 727 cases were reported; 682 meet the national case definition and 35% of those were laboratory confirmed. Prior to mid-March, the few sporadic cases were linked to importations from Europe, but there was continued transmission that peaked in May, and the cases declined after the end of the school year in late June. However, cases continued to persist through Aug. 3.
In Auckland some doctors are calling for a national mass vaccination to control the spreading outbreak. The central Auckland and Waitemata health districts have been worst affected in an outbreak since May. By last week, 250 cases had been reported. Waikato has been affected since July, with more than 20 cases and many other areas have had sporadic cases of the highly infectious viral disease. Of the 29 new cases of confirmed or probable measles reported last week, 19 were from the Auckland region. The remainder were in six other health districts from Northland to Southland.
“There has to be a serious look at the control of the current outbreak,” said pediatric infectious diseases specialist Professor Diana Lennon, of Auckland University. “The main option is to do a mass campaign, to consider vaccinating everybody from one year of age to the end of school. We've got to mop up the years and years and years of poor vaccine delivery,” she said.
The director of the Immunization Advisory Centre at Auckland University, Dr Nikki Turner, agreed on the need for catch-up work to fill in the gaps in the national coverage with measles, mumps and rubella (MMR) vaccination. She said although New Zealand now had reasonably high coverage of young children - 90 per cent of 2-year-olds were up-to-date with their immunizations - there were big gaps among older children and young adults. “So throughout New Zealand we've got pockets of people who are not immunized, who can transmit measles. A lot of people still have this myth that measles is a disease of young children, but we're seeing measles in adults, young adults, older adults, older kids.”
The clinical director of primary care at the Auckland and Waitemata District Health Boards, Stuart Jenkins, said the regional public health service had ceased tracing measles cases because the boards had decided it was now better to increase vaccination.
“For the past few months, the ministry has been encouraging general practitioners to increase measles immunization as much as they are able to," said deputy public health director Dr Darren Hunt.