A booster shot to prevent pertussis or whooping cough among middle school-aged kids is found to offer only limited protection, according to a new study.

The study conducted by researchers at Kaiser Permanente's Vaccine Study Center was published on Feb. 5 in the journal Pediatrics. It found that although the Tdap booster vaccine is 70 percent effective in protecting a child from whooping cough for the first five years after receiving the shot, the effectiveness level drops after four or more years.

DTap is a vaccine given to children below the age of seven to protect them from the dreaded bacterial diseases: diphtheria, tetanus, and whooping cough. Tdap is the booster that is usually given by age 11 to continue giving the kid protection as they grow.

According to Kaiser Permanente's press release, there is high coverage of whooping cough vaccine, but there is no stopping in the rise of the condition.

To come up with their findings, the researchers gathered data on kids from California aged 10 and above and had received DTap vaccination. More than 96 percent of these kids also received the Tdap booster by the time they reached 14.

Over 1,200 cases of whooping cough in kids were recorded between 2006 and 2015 and most of them also succumbed to the disease during the epidemic in 2010 and 2014, researchers gathered.

Looking at those cases, it was estimated that the booster vaccine was 69 percent effective during its first year. In the following years, immunity waned, and by age three, those kids only had little protection, the researchers said.

According to Dr. Nicola Klein, co-director at the study center, the bottom line is that current vaccine preparations are not as effective as they should be in preventing an epidemic.

But Klein and Dr. Paul Offit, director of the Vaccine Education Center, agree that the current preparations somehow provide short-term protection. The researchers then suggest that instead of making it a routine shot, Tdap should be given at the right time or when an outbreak is imminent.