PhotoJust when you think a chronic illness has been permanently defeated, it sometimes creeps back up. For example, take whooping cough or pertussis, as it’s otherwise known.

This year alone over 21,000 cases of the sickness have been documented by the Centers for Disease Control and Prevention (CDC), which is up from 18,179 cases in 2011. In the last two years nearly 25 children, in some cases babies younger than 1 years of age, have died from whooping cough.

You may ask why the disease has come back with such a vengeance?

According to a study conducted by Kaiser Permanente and recently published in the New England Journal of Medicine, the vaccine for pertussis tends to weaken over time, losing its ability to combat the disease effectively.

Protection wanes

“During the five years after the last dose of vaccine, protection from the disease wanes substantially each year, said Dr. Nicola Klein, co-director of Kaiser’s Vaccine Study Center, and lead author of the report.

“If we estimate that after the fifth dose of vaccine, protection is at 95 percent, protection would decrease to 71 percent after five years. A large part of the reason the epidemics have been occurring here and in other states around the country has to do with this waning immunity in this school-aged population,” she said.

PhotoTom Clark, who is an epidemiologist with the CDC, also revealed other important truths about whooping cough. One: The disease actually never went away, it’s just been somewhat contained compared to many years ago. Two: No one -- especially parents -- should use this particular study as an excuse not to get their children vaccinated, as it’s still our best form of protection against the pertussis disease.

“We want to make sure parents understand that even though the protection wears off more quickly, the vaccine shouldn’t be misconstrued as not being protective,” said Clark. “Pertussis never went away, and it’s back now with a vengeance. And this vaccine protects against severe disease and its complications.”

Pertussis infections usually linger somewhere between one and six weeks, says the CDC, but can also stretch on for longer periods of time. The government agency also states that 50 percent of infants who are younger than one years old and develop whooping cough have to be hospitalized.

The CDC also says that infants should be vaccinated with what’s known as DTaP, and adults, teens and preteens should be protected with what’s known as Tdap.

Weakens over time

Although these vaccines are still considered the first line of defense against whooping cough, scientists have known for quite some time that effectiveness does in fact weaken over time.

This truth was confirmed after Klein and her research team studied the previous findings of two groups of children who both received full whooping cough vaccinations. They first examined 277 children between 4 and 12 years of age with pertussis, and also studied 3,318 children who didn’t have the disease.

Klein and her research team found that 4.5 percent of the 6-year olds who were studied had whooping cough, along with 12.2 percent of the 8-year olds and 18.5 percent of the 10-year olds.

 The research determined that children who didn’t have the disease received their vaccination on a more recent date, confirming the potency of the vaccination diminishes over time. The findings also explained why a higher percentage of the older kids who were studied had pertussis.

According to the CDC, DTaP should be given to children at 2-months of age up until the age of 6. If children haven’t been immunized by age-7, they should receive Tdap, and doses of the vaccine differs depending on how consistent your child has been protected since infancy.  

“In conclusion, our evaluation of data from a large pertussis outbreak in California showed that protection from disease after a fifth dose of DTaP among children who had received only DTaP vaccines was relatively short-lived and waned substantially each year, wrote Klein and her research team. “Our findings highlight the need to develop new pertussis-containing vaccines that will provide long-lasting immunity.”

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