A new whooping cough vaccine has just passed phase 2 clinical trials. An international research team, led by Camille Locht, Inserm research director at the Lille Infection and Immunity Center, published on March 10 in The Lancet results demonstrating the efficacy and safety of this vaccine called BPZE1.
Although two types of vaccines are already widely used against this extremely contagious disease, certain imperfections have led researchers to study alternatives. One of the existing vaccines uses whole germs, i.e. live weakened strains of Bordetella pertussis, the bacteria responsible for whooping cough. Its very high efficacy is marred by notable adverse effects, such as high fevers. This gives favor to a so-called “acellular” vaccine, composed of antigens of Bordetella pertussis with better tolerance, but 15% less efficacy.
However, the two types of vaccines do not completely prevent transmission between individuals, the bacteria still developing in the respiratory system. “Be careful, current vaccines remain very effective and vaccination must be maintained to limit the bacteriological reservoir, which is exclusively human”, emphasizes Camille Locht.
Mimicking natural infection
From the beginning of the 2000s, the Lille researcher and his colleagues began to clear the trail of the nasal passage, then still little used in vaccination. The advantage of this approach, which consists in introducing the product in the form of a spray through the nose, is to mimic the natural infection by Bordetella pertussis that affects the respiratory system. The induced immunity is therefore stronger at this level. “Furthermore, the side effects of whole-cell vaccines come mainly from the intramuscular injection. With the nasal route, the problem is circumvented”, says Camille Locht.
Whooping cough is not the only disease for which such a strategy has been developed. There are already nasal flu vaccines on the market.
Phase 2 of the clinical trials took place in three research centers in the United States, with a cohort of 264 healthy volunteers, aged 18 to 50. The objective was to compare the effects of the BPZE1 vaccine (developed by the American company Iliad Biotechnologies), the acellular vaccine and a placebo. The study was conducted in a randomized and double-blind way, that is to say that neither the participants nor the researchers knew which product was actually delivered. The routes of administration of the vaccines being different, the individuals receiving a dose of BPZE1 by the nasal route had a placebo by the intramuscular route, and vice versa for those receiving the acellular vaccine. To simulate a natural infection in an attenuated way, a dose of BPZE1 was administered three months later to half of the volunteers – the others receiving an intranasal placebo.
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