Pertussis post-exposure prophylaxis among household contacts: a cost-utility analysis.
BACKGROUND
Recent pertussis outbreaks have prompted re-examination of post-exposure prophylaxis (PEP) strategies, when immunization is not immediately protective. Chemoprophylaxis is recommended to household contacts; however there are concerns of clinical failure and significant adverse events, especially with erythromycin among infants who have the highest disease burden. Newer macrolides offer fewer side effects at higher drug costs. We sought to determine the cost-effectiveness of PEP strategies from the health care payer perspective.


METHODS
A Markov model was constructed to examine 4 mutually exclusive strategies: erythromycin, azithromycin, clarithromycin, or no intervention, stratified by age group of contacts ("infant", "child", and "adult"). Transition probabilities, costs and quality-adjusted life years (QALYs) were derived from the literature. Chronic neurologic sequelae were modeled over a lifetime, with costs and QALYs discounted at 5%. Associated health outcomes and costs were compared, and incremental cost-effectiveness ratios (ICER) were calculated in 2012 Canadian dollars. Deterministic and probabilistic sensitivity analyses were performed to evaluate the degree of uncertainty in the results.


RESULTS
Azithromycin offered the highest QALYs in all scenarios. While this was the dominant strategy among infants, it produced an ICER of $16,963 per QALY among children and $2,415 per QALY among adults. Total QALYs with azithromycin were 19.7 for a 5-kg infant, 19.4 for a 10-year-old child, and 18.8 for a 30-year-old adult. The costs of azithromycin PEP among infants, children and adults were $1,976, $132 and $90, respectively. While results were sensitive to changes in PEP effectiveness (11% to 87%), disease transmission (variable among age groups) and hospitalization costs ($379 to $59,644), the choice of strategy remained unchanged.


CONCLUSIONS
Pertussis PEP is a cost-effective strategy compared with no intervention and plays an important role in contact management, potentially in outbreak situations. From a healthcare payer perspective, azithromycin is the optimal strategy among all contact groups.
Division of Infectious Diseases, Children's Hospital of Eastern Ontario, Ottawa, ON, Canada; University of Ottawa, Ottawa, ON, Canada.
Nisha
N
Thampi
Department of Health Services Research and Policy, London School of Hygiene and Tropical Medicine, London, United Kingdom.
Ipek
I
Gurol-Urganci
Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada; Public Health Ontario, Toronto, ON, Canada.
Natasha S
NS
Crowcroft
Public Health Ontario, Toronto, ON, Canada; Institute of Health Policy, Management & Evaluation, University of Toronto, Toronto, ON, Canada; Institute for Clinical Evaluative Sciences, Toronto, ON, Canada; Toronto Health Economics and Technology Assessment Collaborative, Toronto, ON, Canada.
Beate
B
Sander
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003365:Costs and Cost Analysis; D005191:Family Characteristics; D005260:Female; D006801:Humans; D007223:Infant; D018942:Macrolides / Q000009:adverse effects / Q000191:economics / Q000627:therapeutic use; D008297:Male; D008954:Models, Biological; D014917:Whooping Cough / Q000191:economics / Q000453:epidemiology / Q000517:prevention & control
D018942:Macrolides