Researchers in the US are questioning the method through which the United States protects her citizens against whooping cough. The latter is a disease that has killed 11 babies and sickened thousands of people in a major outbreak in 2010.
The current vaccine known as DTaP, which is designed to protect against whooping cough but also tetanus and diphtheria, wanes greatly in efficiency in the five years following the fifth shot given to children as per recommendations from the Centers for Disease control, the study said.
It was carried out in California by the Kaiser Permanente Vaccine Study Center and published in the online version of the New England Journal of Medicine.
In the United States, the CDC recommends children get five shots, starting at two months and with the last coming between the ages of four and six, right before they start school.
The research was the first to focus specifically on a large population of highly vaccinated children who had exclusively received DTaP vaccines since birth and for whom enough time had passed since their fifth dose that the vaccine waning could be assessed.
"The findings suggest that whooping cough control measures may need to be reconsidered. Prevention of future outbreaks may be best achieved by developing new pertussis-containing vaccines or reformulating current vaccines to provide long-lasting immunity," said Nicola Klein, lead author of the study.
In the study, researchers compared 277 children, aged four to 12 and who were positive for whooping cough, with 3,318 children who were negative for pertussis and separately with 6,086 matched controls.
They assessed the risk of pertussis in children from 2006 to 2011 in California relative to the time since the fifth dose of DTaP. The researchers found that protection from pertussis after the fifth dose of DTaP vaccine wanes more than 40 percent each year.
The amount of protection remaining after five years depends heavily on the initial effectiveness of the fifth dose of DTaP, according to Klein.