Background: Pertussis is a highly contagious respiratory disease. Despite a high rate of vaccine coverage through the Dutch national immunization program, the incidence of pertussis remains high in the Netherlands and the risk of infection continues. Because pertussis is most severe in unimmunized infants and infants who have only received some of the recommended doses, new pertussis immunization strategies should be considered to protect this vulnerable population.
Objective: This study was designed to estimate the cost-effectiveness of 3 new immunization strategies for possible addition to the current Dutch national immunization program: immunization of the infant at birth, immunization of the parents immediately after birth of the child (cocooning), and maternal immunization during the third trimester of pregnancy.
Methods: A literature search was performed in the PubMed database for articles published in English, German, and Dutch using the following terms: pertussis, whooping cough, vaccination strategies, maternal immunization, cocooning, at birth, vaccine efficacy, mortality, underreporting, prevalence, incidence, and cost-effectiveness. A decision-tree model was developed for this analysis, and data on pertussis morbidity and costs were collected consistently for different age groups (infants <1 year of age and adults 25 to 34 years of age). The size of the infant cohort was set at 200,000 to approximate previous Dutch birth cohorts. The size of the adult cohort was set at 401,380 parents for the cocooning strategy and 201,380 mothers for the maternal immunization strategy. Health benefits (quality-adjusted life-years [QALYs]) and costs were estimated in both cohorts for each of the 3 immunization strate- gies. Incremental cost-effectiveness ratios were calculated from both a payer's and a societal perspective. The robustness of the results was determined through sensitivity analysis.
Results: In the base-case analysis, cocooning and maternal immunization were found to be effective in reducing the incidence of pertussis among infants (123 and 174 infant cases were expected to be prevented, respectively). Furthermore, cocooning and maternal immunization were estimated to be cost-effective from a payer's perspective (euro4600 [US $6400]/QALY and euro3500 [$4900]/QALY, respectively) and even cost-saving from a societal perspective (savings of up to euro7200 [$10,100] and euro5000 [$7000], respectively). Sensitivity analyses revealed that favorable cost-effectiveness was generally robust. In the sensitivity analysis, the cost-effectiveness of cocooning and maternal immunization was mostly sensitive for changes in assumptions on underreporting (200-fold increase in reported number of symptomatic cases) of pertussis disease and infection. With no underreporting, the ICER was estimated at euro211,900 ($296,700)/QALY for cocooning and euro81,600 ($114,200)/QALY for maternal immunization from a payer's perspective. However, even at much lower levels of underreporting (20- to 30-fold increase in incidence), cost-effectiveness remained favorable. The cost-effectiveness of the third strategy, at-birth immunization, was highly unfavorable (euro329,900 [$461,900]/QALY from a payer's perspective and euro330,100 [$462,100]/ QALY from a societal perspective).
Conclusions: This study estimated that the addition of cocooning or maternal immunization to the current Dutch national immunization program likely would be cost-effective or even cost-saving. These estimates were mainly due to reduction in the number of cases among parents, which are likely to be mild and therefore would largely remain unreported. Immunization at birth was not a cost-effective strategy. Cocooning was the most expensive intervention to implement; however, it resulted in the highest number of QALYs gained (mainly in adults). Maternal immunization would offer better protection of infants, due to maternally acquired antibodies.
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