Protection from pertussis after the Tdap booster vaccine fades quickly in adolescents, providing good protection for about two years, according to results from a recent study in California.
According to “Whooping cough protection fades fast after Tdap booster, study finds,” written by Carina Storrs for CNN, many states require middle school students to receive Tdap boosters — which protect against pertussis, tetanus and diphtheria.
The study found the booster protected about 69% of adolescents against whooping cough in the first year after vaccination, but protection dropped to 57% of adolescents in the second year, then 25% and 9% in the third and fourth years after vaccination, respectively, Storrs wrote.
Researchers with Kaiser Permanente Vaccine Study Center in Northern California looked at diagnosed pertussis infections in about 280,000 children from 2009, when the children were age 10, until 2015, according to the article. Nearly all of the children had received a Tdap booster by the age of 11 or 12 because California required the vaccine for seventh-graders starting in 2011.
“It provides moderate protection during the first year, but years two and three after vaccination, there is not that much protection left,” study lead author Nicola P. Klein, MD, PhD, co-director of the Kaiser Permanente Vaccine Study Center in Northern California, said in the article. Findings from the study were published Feb. 5 ahead of print in the journal Pediatrics.
Researchers hoped the Tdap vaccine would fare better than the five doses of DTaP, which are recommended for all children between 2 months and 4 to 6 years of age, Storrs wrote. Studies have shown that immunity fades starting one year after the last DTaP dose, and so Tdap is given later in adolescence to fill in the gap.
Researchers found most of the cases of pertussis in the study were mild or moderate, according to the article, but they noted the disease still could spread to more vulnerable populations such as infants or younger children.
In the article, Klein suggests healthcare providers look at new strategies for Tdap vaccinations. One such strategy would involve giving the booster to children only if an outbreak appears to be on the horizon, but that would require health departments to keep up with regular surveillance. Another option she mentions in the article is to give boosters to all adolescents every three to four years based on the frequency of outbreaks.
James D. Cherry, MD, MSc, distinguished research professor in the David Geffen School of Medicine at UCLA, said in the article, the bigger concern is how to protect babies — especially those younger than 3 months old — in whom pertussis can be deadly. “The most important thing is to vaccinate pregnant women [because protective antibodies get passed through the placenta] and start immunizing at 6 weeks and not 8 weeks,” Cherry said in the article.
Could there be a better vaccine?
According to the article, Klein said the study offers clues to building a more long-lasting vaccine. Findings from one outbreak showed cases of pertussis were less likely in older adolescents, who had been vaccinated in the 1990s when a different form of vaccine, whole cell pertussis, still was given. That vaccine offered longer protection, according to the article, but it was replaced by acellular pertussis, which had fewer side effects, Storrs wrote.
Cherry and other researchers worldwide are working to modify the vaccine so that it causes fewer side effects and still provides long-lasting immunity, according to the article. The idea would be for it to replace acellular pertussis in childhood and adolescent immunizations, Cherry said in the article. He said new versions are “a long ways away” from being ready to use.
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