The whooping cough vaccine--commonly given as part of the DPT/Tdap trio (diphtheria, pertussis, and tetanus)--loses its effectiveness after about three years, says a preliminary medical study.
Focusing on last year's whooping cough outbreak in California, the Associated Press reports the study showed that children who received the fifth dose within the last three years were less likely to be infected with the sometimes-fatal disease.
It is recommended that children receive five doses of the whooping cough vaccine between the ages of 2 months and 6 years, with a booster shot to be administered at the age of 11 or 12.
Rates of whooping cough are significantly lower in children older than 11 or 12, according to the study. The recommended booster shot may reinforce the vaccine's effectiveness.
While this study may shed some light on why whooping cough semi-frequently reappears at an epidemic level, it is not complete, with the CDC telling the AP that the long-term effectiveness of the booster is unknown.
For this reason, schools across the country--particularly in California--are now making the whooping cough vaccine mandatory for all middle and high school students.
Though the number of cases has dropped significantly over the summer, there is some concern that a return to school will incite another epidemic.
At this point, the only way to prevent such an occurrence is to require the whooping cough vaccine. So even if your child's school doesn't mandate it, you might want to raise the issue with your family physician.