Whooping cough increase related to current vaccine
The move to an artificially created vaccine for whooping cough is behind an increase in cases of the deadly disease in the US, a new study suggests.
The findings highlight the need to do similar research in Australia where whooping cough cases have spiralled upward in the past decade, co-author Associate Professor Manoj Gambhir, from the University of Monash, says.
In 2012 the US saw the highest number of pertussis (whooping cough) cases since 1955.
At the same time there has been a shift in the age group reporting the largest number of cases from adolescents to 7 to 11 year olds.
In the paper, published today in PLOS Computational Biology, Gambhir and colleagues use mathematical modelling of 60 years of pertussis disease data to determine what best explains this increase.
A Change in Vaccine Efficacy and Duration of Protection Explains Recent Rises in Pertussis Incidence in the United States
Published: April 23, 2015
PDF – Study
Over the past ten years the incidence of pertussis in the United States (U.S.) has risen steadily, with 2012 seeing the highest case number since 1955. There has also been a shift over the same time period in the age group reporting the largest number of cases (aside from infants), from adolescents to 7–11 year olds. We use epidemiological modelling and a large case incidence dataset to explain the upsurge. We investigate several hypotheses for the upsurge in pertussis cases by fitting a suite of dynamic epidemiological models to incidence data from the National Notifiable Disease Surveillance System (NNDSS) between 1990–2009, as well as incidence data from a variety of sources from 1950–1989. We find that: the best-fitting model is one in which vaccine efficacy and duration of protection of the acellular pertussis (aP) vaccine is lower than that of the whole-cell (wP) vaccine, (efficacy of the first three doses 80% [95% CI: 78%, 82%] versus 90% [95% CI: 87%, 94%]), increasing the rate at which disease is reported to NNDSS is not sufficient to explain the upsurge and 3) 2010–2012 disease incidence is predicted well. In this study, we use all available U.S. surveillance data to: 1) fit a set of mathematical models and determine which best explains these data and 2) determine the epidemiological and vaccine-related parameter values of this model. We find evidence of a difference in efficacy and duration of protection between the two vaccine types, wP and aP (aP efficacy and duration lower than wP). Future refinement of the model presented here will allow for an exploration of alternative vaccination strategies such as different age-spacings, further booster doses, and cocooning.
FDA NEWS RELEASE – FDA study helps provide an understanding of rising rates of whooping cough and response to vaccination
For Immediate Release: Nov. 27, 2013
A new study is helping to provide a better understanding of vaccines for whooping cough, the common name for the disease pertussis. Based on an animal model, the study conducted by the U.S. Food and Drug Administration (FDA) and published November 25, 2013, in The Proceedings of the National Academy of Sciences, shows that acellular pertussis vaccines licensed by the FDA are effective in preventing the disease among those vaccinated, but suggests that they may not prevent infection from the bacteria that causes whooping cough in those vaccinated or its spread to other people, including those who may not be vaccinated.
While the reasons for the increase in cases of whooping cough are not fully understood, multiple factors are likely involved, including diminished immunity from childhood pertussis vaccines, improved diagnostic testing, and increased reporting. With its own funds plus support from the National Institutes of Health (NIH), the FDA conducted the study to explore the possibility that acellular pertussis vaccines, while protecting against disease, might not prevent infection.
Study- Acellular pertussis vaccines protect against disease but fail to prevent infection and transmission in a nonhuman primate model
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
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
pertussis to unvaccinated contacts. Vaccination with wP induced a more rapid clearance compared with naïve and aP-vaccinated animals. By comparison, previously infected
animals were not colonized upon secondary infection. Although all vaccinated and previously infected animals had robust serum antibody responses, we found key differences in T-cell immunity.
Previously infected animals and wP-vaccinated animals possess strong pertussis-specific T helper 17 (Th17) memory and Th1 memory,whereas aP vaccination induced a Th1/Th2 response instead. The
observation that aP, which induces an immune response mismatched to that induced by natural infection, fails to prevent colonization or transmission provides a plausible explanation for the
resurgence of pertussis and suggests that optimal control of pertussis will require the development of improved vaccine