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Whooping cough vaccine not as powerful as thought

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  • Whooping cough vaccine not as powerful as thought


    Whooping cough vaccine not as powerful as thought

    The Atlanta Journal-Constitution

    Sunday, March 22, 2009

    A cluster of whooping cough cases among Cobb County (Georgia) elementary students is adding to concerns that an important vaccine isn?t as effective as it needs to be to stop the spread of disease.

    Whooping cough, also called pertussis, is highly contagious and can cause serious illness among infants and very young children. But the vaccine is only about 85 percent effective and wears off over time, leaving a significant number of children and adults vulnerable to an infection that is more common than many realize, health officials said.

    Of the 18 students in the recent Cobb cluster, 17 were properly immunized with five doses of DTaP vaccine, which protects against diphtheria, tetanus and pertussis, health officials said.

    The Centers for Disease Control and Prevention has been studying the Cobb cases. While a better pertussis vaccine is needed, CDC officials said, the available shots are still the best protection against the disease and they reduce the severity of symptoms in people who are infected.

    ?Despite the fact that we routinely vaccinate against pertussis, pertussis is endemic. There?s lots of pertussis,? said Dr. Nancy Messonnier, director of CDC?s meningitis and vaccine preventable diseases branch.

    But scientists are struggling to understand why reports of pertussis cases have risen dramatically since the 1980s. It may reflect more testing or diagnosis; it may reflect the cyclical nature of the disease. It?s even unclear how often clusters like the one in Cobb occur.

    ?We are frustrated by the fact that we don?t know,? Messonnier said.

    About 10,000 cases and 20 infant deaths were reported in the United States last year, but some studies have suggested the number of people sickened each year may be closer to 300,000, CDC officials said.

    Experts believe the disease is underdiagnosed and underreported in vaccinated school-age children and adults who often have milder symptoms and whose childhood shots have worn off. They believe that adolescents and adults are spreading the disease to vulnerable infants and children.

    In an effort to stop this under-the-radar disease transmission, the CDC about four years ago began recommending that adults and adolescents get pertussis booster shots.
    The goal is to increase ?herd immunity? ? the more people who are immune, the harder it is for the disease to spread to those who aren?t protected because the vaccine didn?t work for them or because they aren?t vaccinated.

    It?s too early to tell whether the adult and adolescent booster shots will curb the spread of pertussis because it can take years for a significant number to get shots.

    While no vaccine is 100 percent effective, some parents are surprised and angry that a vaccine they trusted is failing to protect some children. And officials with the Georgia Division of Public Health said too many local doctors are not aware the disease is circulating in the community and can infect fully vaccinated children.

    Earlier this month, the state health department sent a blast fax to area pediatricians and family doctors alerting them to be on the lookout for pertussis.

    East Cobb parent Laurie Wood assumed her children were protected because they?d received all the shots. Then her 8-year-old son, Charlie, developed a cough so severe it caused him to vomit. In January, Charlie was diagnosed with pertussis.

    ?I was scared because he?s been vaccinated,? Wood said last week. ?I also was mad because if the vaccination wasn?t working, we should have known about it.?

    So far this year, 48 pertussis cases have been reported in Georgia, continuing an uptick in reports to state health officials that began last year when 103 cases were reported. Five Georgia infants have died from whooping cough since 2004.

    Whooping cough starts with coldlike symptoms, but after a week or two, a severe cough can develop. Children can cough violently until all the air in their lungs is gone and they inhale with a ?whooping? sound.

    Between August and February, 18 cases were reported at four elementary schools in the Cobb County School District, including two third-graders at Mountain View; two second-graders and two fourth-graders at Garrison Mill; and three first-graders at Timber Ridge. Nine children had the disease at Rocky Mount Elementary: three third-graders, three fourth-graders and three fifth-graders.

    Wood?s son Charlie is a third-grader at Kincaid Elementary ? just a few miles from Mountain View.

    It was somewhat surprising that so many of the cases involved young children who were fully vaccinated, said Stacey Martin, a CDC epidemiologist who was involved in investigating the cluster.

    Nationally, school-age children diagnosed with the disease are generally teenagers, which is what prompted a CDC advisory panel in 2005 to recommend an additional pertussis booster shot at age 11 or 12.

    To try to determine the magnitude of the problem at the four Cobb schools, last month CDC and local health officials gave voluntary pertussis tests to 108 children and staff who were currently coughing, and 22 of them showed evidence of recent infection, said Julie Gabel, a state health department epidemiologist.

    Despite the study?s test results, some doctors refused to believe parents when they said that their children had pertussis. ?More than one said to the parent: ?Well, your child couldn?t have had pertussis, your child?s been vaccinated,? Gabel said, adding that the department is working to educate physicians.

    At the four schools, health officials think the outbreaks are over or winding down. But whooping cough continues to be reported elsewhere. Georgia health officials aren?t aware of any other current whooping cough clusters.

    Dr. Walter Orenstein, a leading vaccine expert, was surprised to hear that the Cobb cluster involved young students who would have received a pertussis booster as they entered school.

    ?The real issue is what the rate of vaccine failure is,? said Orenstein, a former CDC official who recently became deputy director for vaccine preventable diseases at the Gates Foundation in Seattle.

    It?s possible, Orenstein said, that the sick children were simply among the expected 15 percent of people immunized that the vaccine fails to protect.

    Despite concerns about pertussis, the reported cases are still far fewer than before a vaccine became available.

    In the 1920s and 1930s, there were more than 160,000 cases and more than 5,000 deaths each year. After the introduction of a pertussis vaccine in the 1940s, reports dropped dramatically. In 1976, just 1,010 cases were reported ? the record low.

    Whether it?s possible to develop a more effective pertussis vaccine is a matter of scientific debate. But Dr. John Robbins, a scientist at the National Institutes of Health, has urged in scientific journals that a more effective vaccine be made using a different way of creating the component that produces immunity.

    ?I think we?d probably get rid of the disease,? Robbins said.

    Vaccine manufacturers aren?t looking for more effective vaccine because the current one is ?good enough? ? especially once more adolescents and adults start getting booster shots, said Dr. Michael Decker, a vice president at Sanofi Pasteur. His company and GlaxoSmithKline make pertussis vaccines.

    Decker said there?s nothing unusual about the Cobb cluster. Until the U.S. population is more thoroughly vaccinated and receiving booster shots, he said, such clusters will occasionally occur across the country. ?I look at this and see absolutely nothing remarkable,? he said.



    Despite concerns about pertussis, the reported cases are still far fewer than before a vaccine became available.

    In the 1920s and 1930s, there were more than 160,000 cases and more than 5,000 deaths each year. In the 1940s, after the introduction of a pertussis vaccine, reports dropped by more than 99 percent. In 1976 just 1,010 cases were reported ? the record low.


    2009* 48

    2008 103

    2007 37

    2006 102

    2005 78

    2004 71

    2003 n/a


    2009* 1,699

    2008 10,007

    2007 10,454

    2006 15,631

    2005 25,617

    2004 25,827

    2003 11,647

    * Year so far

    Source: CDC and Georgia Division of Public Health