The whooping cough booster vaccine known as Tdap gradually loses its potency, researchers have recently determined.
The worrisome findings have been featured in the journal Pediatrics on Friday, February 5, and were based on a study led by Dr. Nicola Klein, research scientist and co-director of the Vaccine Study Center at Kaiser Permanente Northern California.
The purpose of the analysis was to assess the long-term effectiveness of Tdap, a booster vaccine for that’s commonly used in order to provide immunization against whooping cough (pertussis).
Preventive shots meant to ward off whooping cough were first administered in the 1940’s, and involved using a whole-cell vaccine consisting of dead cells, pertaining to the pertussis bacteria (Bordetella pertussis).
While this vaccine proved extremely beneficial in preventing whooping cough outbreaks, it had some troubling side effects, such as extremely high fever, capable of causing convulsions.
That’s why in 1991, an “acellular” vaccine called DTaP was created: this type of immunization was based on dead cellular material, instead of entire cells, and was therefore believed to be safer and more hypoallergenic than its predecessor.
The DTaP vaccine is normally administered in 5 doses throughout childhood: the first shot occurs when the baby is 2 months old, the following two happen at intervals of 2 months, the fourth is given between the age of 12 months and 18 months, while the last is offered when the child is between 4 and 6 years old.
Unfortunately however, DTaP only has a success rate of around 80%, lower by around 10% in comparison with that of the original formula. In addition, its effect begins to wear off approximately a year following the last dose.
As a result, in 2006 Tdap was also introduced for 11-year olds and 12-year olds, in order to function as a booster vaccine against pertussis. The vaccine even became mandatory in California starting from 2011, but it appears this type of immunization also loses its usefulness in the long run.
By reviewing medical data recorded between January 2006 and March 2015 regarding 280,000 California teenagers, researchers could identify a total of 1,200 instances of whooping cough, even though before and during that study period immunization efforts had been quite extensive.
Even worse, there were also 2 major outbreaks, in 2010 and 2014, which shows that Tdap failed to offer kids the protection they needed against this extremely contagious disease.
In fact, as scientists have measured, the booster vaccine’s potency a year after being administered was of just 69%.
After 2 years had passed, the effectiveness decreased to 57%, and in the next two years this downward trend was even more staggering, with Tdap success rates being calculated at 25% and 9%, respectively.
While study authors had expected the booster vaccine to become more ineffectual as time went by, they never anticipated results would be so dismal after just 4 years.
Following this surprising discovery, Dr. Nicola Klein and her colleagues are now arguing that Tdap should no longer be routinely administered to preteens.
Instead, given that it provides adequate protection at first, without being too reliable after a lengthier period of time, the whooping cough booster vaccine should be used solely when local outbreaks are considered imminent by health officials.
Alternatively, the shots could be provided to teenagers once every 3 to 4 years, since this is usually the periodicity for pertussis outbreaks.
Also, as study authors point out, it is imperative to develop another type of whole-cell immunization against this highly contagious bacterial disease, given that current preventive shots are so obviously deficient.
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