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Investigational acellular pertussis vaccine effective in adolescents, approved in Thailand
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Recent phase 2/3 data showed that a new recombinant acellular pertussis booster vaccine administered alone or in combination with tetanus and reduced-dose diphtheria vaccines was noninferior to a comparator vaccine in adolescents.
“To our knowledge, this is the first study to assess the effect of a genetically inactivated two-component acellular pertussis vaccine in adolescents primed with whole-cell pertussis vaccine in infancy, and to investigate both a monovalent (pertussis-only) formulation and the vaccine in combination with tetanus and reduced-dose diphtheria vaccines,” Sirintip Sricharoenchai, MD, of the pediatric infectious diseases unit at Medicine Siriraj Hospital in Bangkok, Thailand, and colleagues wrote in The Lancet Infectious Diseases.
According to the researchers, fast-waning immunity of current acellular pertussis vaccines has led to a resurgence of pertussis, or whooping cough, in recent years. As a result, repeated booster vaccination and vaccination during pregnancy is often recommended to maintain immunity in the community and protect newborns during the first few months of life.
“Although these strategies might offer a short-term solution, improved pertussis vaccines are needed that induce more effective and long-lasting protection than available vaccines,” they wrote.
For their trial, the researchers compared the efficacy of a new monovalent recombinant vaccine and tetanus-diphtheria-acellular pertussis (TdaP) vaccine — both of which were developed by BioNet-Asia and contain 5 g of genetically inactivated pertussis toxin and 5 g of filamentous haemagglutinin — with a comparator Tdap vaccine (Adacel, Sanofi Pasteur) containing 2.5 g of chemically inactivated pertussis toxin, 5 g of filamentous hemagglutinin, 3 g of pertactin and 5 g of fimbriae types 2 and 3. They randomly assigned 450 healthy adolescents aged 12 to 17 years to receive the monovalent (n = 150), new TdaP (n = 150) or comparator vaccine (n = 150) between July 6 and Aug. 20, 2015. The primary outcome was the proportion of patients with seroconversion rates for pertussis toxin and filamentous hemagglutinin IgG antibodies 28 days after vaccination. The researchers established a noninferiority margin of 10%.
Twenty-eight days after vaccination, seroconversion rates for antipertussis toxin IgG (96.6% vs. 55%; 41.6% difference; 95% CI, 33.1-50.1) and antifilamentous hemagglutinin (82.6% vs. 54.4%; 28.2% difference; 95% CI, 18.1-38.2) were higher among patients who received the new TdaP vaccine vs. those who received the comparator Tdap vaccine. Seroconversion rates were also higher for antipertussis toxin IgG (96%; 40.9% difference; 95% CI, 32.3-49.5) and antifilamentous hemagglutinin (93.2%; 38.9% difference; 95% CI, 29.9-47.8) with the monovalent vaccine vs. the comparator vaccine.
The incidence of adverse events was similar in all three vaccine groups. The most common adverse events included pain in the limbs (n = 5) and myalgia (n = 5).
Following these results, the two investigational pertussis vaccines were approved as booster immunizations for adults and adolescents in Thailand, according to the researchers. The monovalent vaccine is available under the brand name Pertagen and the new TdaP vaccine is available under the brand name Boostagen.
“The availability of recombinant monovalent pertussis vaccines inducing high antibody responses provides the medical community and consumers with the opportunity to vaccinate against pertussis when immunization against diphtheria and tetanus is not required or not desired, such as repeated maternal immunizations to protect newborn babies against pertussis,” the researchers wrote. “Studies are underway to pave the way for licensure studies of this acellular pertussis vaccine in countries other than Thailand, including trials in Europe and follow-up studies to prove the long-lasting protection induced by these new-generation recombinant pertussis vaccines.”
In a related editorial, Carl Heinz Wirsing von König, MD, director of the Institute of Hygiene and Laboratory Medicine at Helios Klinikum Krefeld, Germany, said it will be important to determine the long-term efficacy of the vaccines and how they perform in patients primed with other acellular pertussis products.
“This vaccine study is a first step in identification of how acellular pertussis vaccines could be improved. However, before we can really hope for an acellular vaccine 2.0, many more data and studies are necessary and other avenues should be explored,” he wrote. “For now, it is important to keep in mind that currently licensed acellular and whole-cell pertussis vaccines are efficacious and safe, and that only by maintaining high immunization coverage rates with the available vaccines can pertussis be kept at bay.” – by Stephanie Viguers
Disclosures: Heinz Wirsing von König reports receiving personal fees from GlaxoSmithKline and Sanofi Pasteur. Sricharoenchai reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.
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