Whooping cough increase related to current vaccine

For Immediate Release: Nov. 27, 2013
FDA study helps provide an understanding of rising rates of whooping cough and response to vaccination
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.
Whooping cough rates in the United States have been increasing since the 1980s and reached a 50-year high in 2012. Whooping cough is a contagious respiratory disease caused by Bordetella pertussis bacteria. Initial symptoms include runny nose, sneezing, and a mild cough, which may seem like a typical cold. Usually, the cough slowly becomes more severe, and eventually the patient may experience bouts of rapid, violent coughing followed by the “whooping” sound that gives the disease its common name, when trying to take a breath. Whooping cough can cause serious and sometimes life-threatening complications, permanent disability, and even death, especially in infants and young children.

19 kids in Summit Co. diagnosed with whooping cough despite being up to date on vaccinations
PARK CITY, Utah — A whooping cough outbreak is causing concern in Summit County as 19 children have been diagnosed, and it’s the first time in years Park City schools have seen a case of pertussis.
Officials said all of the children who have been diagnosed were vaccinated against the illness.
“It has been a very busy week, very busy week here, a lot of people coming in to be tested,” said Dr. Alison Delgado with Summit Pediatrics.
Delgado tested dozens of children for whooping cough in the last week. According to the Summit County Department of Health, there are 19 confirmed cases of the highly contagious illness in Park City, and all of the children infected are up to date on their vaccinations.
“A lot of people want to know why their child is getting it because they’re vaccinated, and it has to do a lot with the vaccine; it’s not a 100 percent, however it is about 90 to 95 percent effective,” said Carolyn Rose, who is a nursing director for the Summit County Department of Health.

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.
Their research finds the level of protection of the currently used acellular vaccine is lower than that of the previously used whole-cell vaccine.
Gambhir says the original whole-cell vaccine developed in 1942 was very effective.
Following introduction of vaccination, the reported disease incidence in the US dropped from 150 cases per 100,000 each year before 1940, to the point of near elimination in the mid-1970s when there were just 0.5 reported cases per 100,000 population.
“Now in the past decade we have seen a rise from that low to about 10-20 cases per 100,000,” says Gambhir.
Gambhir, who led the study with Dr Thomas Clark at the Centers for Disease Control and Prevention, in Atlanta, Georgia, and Professor Neil Ferguson, of the Imperial College London in the UK, says while the number of cases remains low the trend is upward.
“It’s the sort of five-year by five-year rise that is the concern because the worry is it could go back to those levels at which we would start seeing infant deaths,” he says.
New vaccine to blame
Gambhir says in 1991 researchers developed a new vaccine to address public concerns that the whooping cough vaccine caused a reaction in some children.
This vaccine, known as acellular pertussis vaccine, used particular components of the bacteria that were believed to generate the immune response, but was essentially artificially created.
Gambhir says the impact of the change in vaccine has taken time to show in the data.
“You didn’t see an immediate increase [in whooping cough],” he says. “It has taken cohorts of children to have all of their doses to be the new vaccine for the increases in disease to manifest themselves.”
Gambhir says the efficacy of the acellular vaccine is still high – around 80 per cent protection for the first three doses – but there has been a “significant drop” when compared with the older whole-cell vaccine (90 per cent protection).

Study: A Change in Vaccine Efficacy and Duration of Protection Explains Recent Rises in Pertussis Incidence in the United States
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.

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