PEDIATRICS Vol. 112 No. 5 November 2003, pp. e348-e348

Decrease in Hospital Admissions for Febrile Seizures and Reports of Hypotonic-Hyporesponsive Episodes Presenting to Hospital Emergency Departments Since Switching to Acellular Pertussis Vaccine in Canada: A Report From IMPACT

Nicole Le Saux, MD*, Nicholas J. Barrowman, PhD{ddagger}, Dorothy L. Moore, MD, PhD§, Sharon Whiting, MD*, David Scheifele, MD|| and Scott Halperin, MD for Members of the Canadian Paediatric Society/ Health Canada Immunization Monitoring Program–Active (IMPACT)

* Department of Pediatrics, University of Ottawa, Ottawa, Ontario, Canada
{ddagger} Chalmers Research Group, Children’s Hospital of Eastern Ontario Research Institute, Ottawa, Ontario, Canada
§ Montreal Children’s Hospital, McGill University Health Centre, Montreal, Quebec, Canada
|| British Columbia’s Children’s Hospital, Vancouver, British Columbia, Canada
IWK Health Center, Halifax, Nova Scotia, Canada

Objective. Acellular pertussis vaccines were introduced with the promise of an improved safety profile compared with whole-cell vaccines. In 1997–1998, Canada adopted 1 combination acellular pertussis vaccine, having previously used 1 particular combination whole-cell pertussis vaccine. We hypothesized that the change would result in a decrease in hospitalization rates for seizures and reports of hypotonic-hyporesponsive episodes (HHEs) temporally related to pertussis vaccination.

Methods. Active surveillance was performed between 1995 and 2001 by the Immunization Monitoring Program–Active monitors at 12 hospitals using standard case definitions. Seizures had to occur within 72 hours after immunization with a pertussis-containing vaccine or 5 to 30 days after immunization with measles-mumps-rubella vaccine. HHE episodes had to occur within 48 hours of receipt of a pertussis-containing vaccine. Poisson regression models were used to compare the average number of monthly admissions for seizures and HHEs before and after introduction of the acellular pertussis vaccine.

Results. We found a 79% decrease in febrile seizures associated with receipt of pertussis vaccine but no significant decrease in febrile seizures temporally related to measles-mumps-rubella between 1995–1996 and 1998–2001. There was a 60% to 67% reduction in HHEs associated with pertussis-containing vaccines between the same time periods, depending on case definition.

Conclusions. The risks of febrile seizures and HHEs after pertussis-containing vaccine declined significantly with the introduction of acellular pertussis vaccine in Canada. Active surveillance systems are important for detecting trends in uncommon adverse events after routine immunizations.

A quote from researcher David Geier, MD, PhD: "We went to Atlanta," he continues, "to the CDC, and looked at the VSD [Vaccine Safety Data] data. There is  thimerosal-containing DTaP [diphtheria, tetanus and pertussis vaccine] and thimerosal-free DTaP, so we asked a question: Among children that got a minimum of  either three consecutive thimerosal-containing DTaPs or   three consecutive thimerosal-free DTaPs, was there a difference in the number of autism cases in the two groups? We found mega differences. More than 20 times higher. The rate of autism in the children that got more than three doses of thimerosal-containing DTaP  vaccines was much, much higher. Almost all the children that   have autism in that group were the ones that got the thimerosal-containing DTaP vaccine. The more  thimerosal the greater the cases of autism."
   --O'Meara KP. CDC Study Raises Level of Suspicion.

 Posted on Wed, Nov. 08, 2006 by Sun Herald.com


MSU studies safer vaccine
Current ones may damage


STARKVILLE - Biologists at Mississippi State University are studying safer vaccines for whooping cough, which can sometimes lead to brain damage or death. Lakshmi Pulakat and Nara Gavini head up a research team that discovered a mechanism in current vaccines that may trigger neurological damage among whooping cough patients. Whooping cough is caused by the bacterium Bordetella pertussis, which produces various toxins upon infection, said Mary Hetrick, a member of the MSU research team and a biological sciences doctoral student.

"Neurological damage is a dangerous after-effect among patients suffering from whooping cough and also seems to affect infants vaccinated with DPT vaccine or acellular vaccine," said Hetrick. Hetrick said Pulakat and Gavini "have identified a novel mechanism by which the pertussis toxin can exert its ill effects and contribute to brain damage. Since this mechanism is significantly different from the conventional understanding of the action of pertussis toxin, this study provides new possibilities to generate safer acellular vaccines to combat whopping cough," she said.

 2006 The Sun Herald and wire service sources. All Rights Reserved.


Study: Whooping cough vaccination fades in 3 years
ATLANTA, Mon Sep 19, 05:02 PM

An empty bottle of Tetanus, Diphthera and Pertussis, (whooping cough) vaccine is seen at Inderkum High School in Sacramento....More

The whooping cough vaccine given to babies and toddlers loses much of its effectiveness after just three years - a lot faster than doctors believed - and that could help explain a recent series of outbreaks in the U.S. among children who were fully vaccinated, a study suggests.

The study is small and preliminary, and its authors said the results need to be confirmed through more research. Nevertheless, the findings are likely to stir debate over whether children should get a booster shot earlier than now recommended.

"I was disturbed to find maybe we had a little more confidence in the vaccine than it might deserve," said the lead researcher, Dr. David Witt, chief of infectious disease at the Kaiser Permanente Medical Center in San Rafael, Calif. Witt presented his findings Monday at a medical conference in Chicago.

The study was done in California, where whooping cough vaccinations are a hot-button issue. The state had a huge spike in whooping cough cases last year, during which more than 9,100 people fell ill and 10 babies died after exposure from adults or older children. California schools have turned away thousands of middle and high school students this fall who haven't gotten their booster shot.

Government health officials recommend that children get vaccinated against whooping cough in five doses, with the first shot at age 2 months and the final one between 4 and 6 years. Then youngsters are supposed to get a booster shot around 11 or 12. That means a gap of five to eight years.

Witt's study looked at roughly 15,000 children in Marin County, Calif., including 132 who got whooping cough last year. He found that youngsters who had gone three years or more since the last of their series of shots were as much as 20 times more likely to become  infected than children who had been more recently vaccinated. The largest number of cases was in children 8 to 12 years old.

Whooping cough, or pertussis, is a highly contagious bacterial disease that in rare cases can be fatal. It leads to severe coughing that causes children to make a distinctive whooping sound as they gasp for breath.

Marin County has a reputation for anti-vaccine sentiment, and Witt said that when he started the study he expected to see the illness concentrated in unvaccinated people. But more than 80 percent of the children who developed whooping cough in Witt's study were fully vaccinated.

California health officials told doctors last year that they could give the booster to kids as young as 7 in an effort to stifle the outbreaks. Federal health officials said that they are still studying the issue and that it is too soon to make that a standard practice.

At the Centers for Disease Control and Prevention, which makes recommendations on childhood shots, officials acknowledged that the vaccine's protection declines, but they said the agency's own studies show the drop-off is not as pronounced as Witt's research found.

The CDC has estimated that the risk of the disease can increase fourfold several years after vaccination, not 10 to 20 times. One reason may be differences in how a case is defined: Witt counted positive test results, while the CDC also requires more than a week of symptoms.

CDC officials stressed that the vaccination is still much better than nothing - it reduces how sick a child becomes. Also, the nation no longer sees thousands of whooping cough deaths each year, as it did before there was a vaccine.

The shots "are still our best protection against pertussis, and they still protect well against fatal disease," said Dr. Tom Clark, who leads the CDC's epidemiology team focused on vaccine-preventable diseases. A vaccine using killed bacteria was used for decades, but the nation switched over to a new type in the late 1990s that was seen as less likely to cause the arm soreness, fever and more severe side effects associated with the older version. The vaccine is typically given in a combination shot that also protects against tetanus and diphtheria.

Periodic outbreaks still occur in places with high vaccination rates.

The short-term effectiveness of the vaccine has been shown to be 90 percent or higher in the first couple of years, and nearly every state requires children to get the full series of shots before enrolling in school. The long-term effectiveness is not well understood, but researchers thought it was more than three years.

A preliminary study conducted by the CDC last year found the five-dose vaccination for children was about 70 percent effective five years after the last shot. Witt's research suggests the effectiveness may drop much lower than that, perhaps below 50 percent after just three years.

Witt also found that shots work great in the short term. Rates of whooping cough dropped dramatically after kids were age 11 and 12, when many get the booster shot. The long-term effectiveness of that booster also is not known and has received relatively little study. Health officials are also discussing whether additional boosters may one day be recommended for teenagers or adults.

"It's a little too soon to say much" about the longer-term effectiveness of that booster, said Lara Misegades, a CDC epidemiologist.



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