Whooping cough vaccine not as powerful as thought
By ALISON YOUNG, The Atlanta Journal-Constitution
Sunday, March 22, 2009

A cluster of whooping cough cases among Cobb County 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...

... "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...

... 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...

Regarding the statement above about vaccine effectiveness, its a topic that we will explore further. How is the effectiveness of a vaccine calculated or worked out? What assumptions are made? How accurate is this claim of efficacy and how can it be known that it was actually the vaccine that was the preventative factor and not other factors? When you actualy look at the assumptions they make behind the calculations of vaccine efficacy, you realise how shaky these claims are.

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."...

...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.

Source: AJC.Com