Acellular pertussis vaccine is shown to prevent symptoms
in vaccine recipients while NOT preventing transmission
of the bacterium to other individuals.
AAAS article summary of how the study was set up: The current study goes a step further and suggests that people who get the newer vaccine may still become infected and spread the germ. Tod Merkel, a microbiologist, and colleagues at the Food and Drug Administration in Bethesda, Maryland, examined response to the acellular vaccine in infant baboons, an animal that responds to the bacterium responsible for pertussis similarly to people. The researchers infected four groups of baboons, each group containing three or four babies, by anesthetizing the animals and dripping a pertussis-containing solution into their noses. One group had already received the standard three doses of the acellular vaccine; a second received the whole-cell vaccine. Members of the third group had previously had whooping cough. Those in the fourth group had not had the disease and received no vaccine before being exposed.
AAAS article summary of vaccine efficacy for the individual: As expected, the unvaccinated baboons developed severe whooping cough, while the baboons that had been sick previously remained well, the research team reports today in the Proceedings of the National Academy of Sciences. Both groups of vaccinated animals also remained healthy. However, the germ persisted an average of 35 days in the throats of baboons vaccinated with the acellular shot, though it grew less thickly than it did in the throats of the sick, unvaccinated animals. Baboons vaccinated with the whole-cell shot harbored the germ for 18 days, and it did not grow at all in animals that previously had recovered from pertussis.
PNAS article summary of vaccine efficacy for the community: Pertussis rates in the United States have been rising and reached a 50-y high of 42,000 cases in 2012. Although pertussis resurgence is not completely understood, we hypothesize that current acellular pertussis (aP) vaccines fail to prevent colonization and transmission. To test our hypothesis, infant baboons were vaccinated at 2, 4, and 6 mo of age with aP or whole-cell pertussis (wP) vaccines and challenged with B. pertussis at 7 mo. Infection was followed by quantifying colonization in nasopharyngeal washes and monitoring leukocytosis and symptoms. Baboons vaccinated with aP were protected from severe pertussis-associated symptoms but not from colonization, did not clear the infection faster than naïve animals, and readily transmitted B. pertussis to unvaccinated contacts.
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