September 13, 2012

Whooping Cough Vaccine Less Effective After 5 Years, Booster Shots Suggested

Michael Harper for — Your Universe Online

In the early years of life, children are given immunization shots against all types of potential dangerous illness, including whooping cough, or acellular pertussis. According to a new study, however, children older than 6 and even some teenagers could benefit from an extra round of booster shots.

“We found that the effectiveness of the vaccine wanes 42% on average each year during the five years after the fifth dose," said Dr. Nicola Klein, lead author of a study concerning the effectiveness of the whooping cough vaccine. This study was published in today´s New England Journal of Medicine.

Without a longer-lasting vaccine available, Dr. Klein suggests parents should continue to vaccinate their children saying, “parents should know that some protection is better than no protection."

Dr. Klein and her team were the first to study such a large population of children who had received the diphtheria, tetanus, acellular pertussis (or DTaP) vaccine since birth and for whom enough time has passed to evaluate the effectiveness of these shots.

These researchers were prompted to conduct this study following a recent outbreak of whooping cough cases in California in 2010.

Dr. Klein and team compared 277 4 to 12-year old children with positive signs of whooping cough versus 3,318 children of the same age who did not have the cough. The team then compared both groups of children to a control group of more than 6,000 children. In comparing these groups of children, the researchers found that protection from whooping cough after the fifth dose of the DTaP vaccine can decrease by as much as 40%. Furthermore, the amount at which this protection decreases depends heavily upon the effectiveness of the fifth and final dose, said Dr. Klein. For instance, if the initial and final dose of DTaP was 95% effective in protecting against whooping cough, this effectiveness would decline dramatically – up to 71% – after 5 years. If the initial effectiveness was 90%, the effectiveness of the DTaP would only decline by as much as 42%.

“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 Klein in a statement.

“That said, the DTaP vaccine is effective and remains an important tool for protection against whooping cough for children and the communities in which they live, and following current CDC recommendations remains important.”

Currently, the Center for Disease Control (CDC) recommends giving children 5 DTaP shots at 2, 4 and 6 months of age. The fourth shot should ideally be given between 15 and 18 months of age, with the final shot administered between ages 4 and 6.

Though this study has revealed that the current vaccine isn´t performing as well as some doctors would like, Dr, Klein concluded her study by saying she is hopeful this study will encourage drug manufacturers to start working on a better, more effective version of the vaccine.

"Prevention of future outbreaks will be best achieved by developing new pertussis-containing vaccines that provide long-lasting immunity.”