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Type: Theses
Title: Determinants of severe pertussis infection in Australian children and awareness and uptake of pertussis vaccination in adults
Author: Clarke, Michelle
Issue Date: 2016
School/Discipline: School of Public Health
Abstract: Despite long standing immunisation programs, pertussis remains a challenging disease in Australia and globally, with young infants most at risk of death and severe disease. Globally, the emergence of pertactin negative strains of Bordetella pertussis has been observed, with implications unclear. Adults are a common reservoir of infection and a source of transmission to young infants, and vaccine coverage in this group is largely unknown. In this research program, we aimed to: 1. Describe the clinical severity of Bordetella pertussis infections in Australian children and investigate factors associated with severe disease; 2. Describe the impact of genotypic variants lacking pertactin expression on severity of pertussis infections in children; and 3. Assess community knowledge and awareness of pertussis infections and predictors of uptake of recent pertussis vaccination in the South Australian population. Methods: 1. Medical, laboratory and vaccination records were reviewed for children admitted to hospital with a diagnosis of pertussis at any of eight participating tertiary paediatric hospitals around Australia. A severity scoring system was designed and used to determine predictors of severe pertussis disease in the enrolled children. 2. To assess the influence of emerging B. pertussis variants deficient in pertactin antigen, clinical details were collected from medical records of children presenting to, or admitted to one of three major paediatric hospitals in Australia (Women’s and Children’s Hospital, Adelaide, Princess Margaret Hospital, Perth, Children’s Hospital at Westmead, Sydney) during 2008-2012 with a confirmed pertussis infection and an isolate available for determination of pertactin expression and genotyping. 3. A cross-sectional survey of randomly selected households was conducted in South Australia by Computer Assisted Telephone Interviews to ascertain pertussis (whooping cough) vaccination history and predictors of recent vaccine uptake (within previous five years) amongst South Australian adults. Knowledge, perceptions and attitudes towards pertussis infections and prevention were evaluated. Log binomial models were fit to assess predictors of awareness of adult pertussis vaccine availability Results: 1. One hundred and twenty children who were hospitalised with pertussis were enrolled nationally. Over 40% of cases were in children less than two months of age. A pertussis severity score (PSS) was determined for all cases with the majority of children classified as not severe (PSS ≤ 5). Young age (< two months, p=0.014), presence of fever at admission (p=0.030), presence of co-infection (p=0.004) and prematurity (p=0.024) were associated with more severe disease. 2. A total of 199 B. pertussis isolates collected during 2008-2012 were identified from children presenting to, or admitted to, one of the three participating hospitals. One third of these isolates (35.7%; 71/199) were pertactin deficient. Over one third of cultured cases were from children less than three months of age (n=82/199; 41.2%). Most severe disease occurred in young, unimmunised infants. Adjusting for pertussis toxin promoter allele, vaccination status and age category, Prn status was not associated with disease severity (Risk Ratio=0.97, 95%CI: 0.57-1.62, p=0.90). 3. From 3124 randomly sampled contactable households, 1967 interviews with individuals aged 18-93 years were conducted (participation rate 63%), including 608 parents of children aged < 18 years. Recent adult pertussis vaccine coverage was low, with only 10% of respondents reporting pertussis vaccination in the previous five years. Predictors of recent pertussis vaccination included higher education, larger household size, perception of greater disease severity and discussion with a family physician about pertussis vaccination. The majority of respondents (97%) had heard of pertussis (whooping cough) and many (73%) considered whooping cough to be highly contagious and severe for infants (89%). Whilst 61% of respondents were aware of the availability of an adult pertussis booster vaccine, only 8% (n=154) reported their general practitioner had discussed it with them. If provided free, 77% agreed that they would be more likely to accept a booster pertussis vaccination. Conclusion: B. pertussis infections continue to pose a threat to Australian children, particularly infants too young to have received direct protection through vaccination. Children admitted to hospital with Bordetella pertussis and fever or co-infection should be closely monitored, particularly if they have a history of prematurity. The rapid emergence of pertactin negative Bordetella pertussis variants do not appear to be associated with any increased severity of disease for children, however the impact of strain evolution on vaccine efficacy and transmissibility requires further investigation. Whilst knowledge regarding transmission and severity of Bordetella pertussis was high in the general community, uptake of adult pertussis vaccination is remarkably low amongst South Australians. Improved awareness regarding the availability of a booster pertussis vaccine through general practitioners and/or provision of funded pertussis vaccination for adults has the potential to improve pertussis vaccine coverage and provide greater protection for vulnerable infants.
Advisor: Marshall, Helen Siobhan
Giles, Lynne Catherine
Dissertation Note: Thesis (M.Phil.) (Research by Publication) -- University of Adelaide, School of Public Health, 2016.
Keywords: pertussis
whooping cough
severity
genotype
vaccination
Provenance: Copyright material removed from digital thesis. See print copy in University of Adelaide Library for full text.
This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at: http://www.adelaide.edu.au/legals
DOI: 10.4225/55/5900056249013
Appears in Collections:Research Theses

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