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Adult Vaccination Strategies for Invasive Pneumococcal Disease


Kevin L. Carter

Although the 23-valent pneumococcal polysaccharide vaccine (PPSV23) has been recommended for prevention of invasive pneumococcal disease (IPD) in adults since 1983, there have been no conclusive assessments of its ability to prevent nonbacteremic pneumococcal pneumonia (NPP), which causes several hundred thousand illnesses annually in the United States. A newer pediatric conjugate vaccine containing 6 additional serotypes (PCV13) is expected to further reduce pneumococcal disease in children and adults. The objective of this analysis [JAMA. 2012;307(8):804-812] was to use decision-modeling techniques to estimate the effectiveness and assess the cost-effectiveness of PCV13 vaccination strategies among adult cohorts ≥50 years of age.

For this analysis, the investigators used a Markov state-transition model with a cycle length of 1 year to examine 6 pneumococcal vaccination strategies developed by a Delphi expert panel process. The 6 strategies were as follows: (1) no vaccination; (2) the present US Advisory Committee on Immunization Practices (ACIP) adult recommendations (vaccinate all persons with PPSV23 at age 65 years, with those who have received PPSV23 before age 65 years for a comorbid condition being recommended to receive another dose at ≥65 years if at least 5 years have passed since the previous dose); (3) substituting PCV13 for PPSV23 in current ACIP recommendations; (4) PCV13 at age 50 years and PPSV23 at age 65 years; (5) PCV13 at ages 50 and 65 years; and (6) PCV13 at ages 50 and 65 years followed by PPSV23 at age 75 years.

Strategies were compared using identical hypothetical cohorts that were tracked as they aged. The authors used a lifetime time horizon, a societal perspective, and a 3% discount rate for costs and benefits, converting costs to 2006 US dollars. Quality of life was modeled using health state utility weights, with 0 equaling death and 1 denoting perfect health; quality-adjusted life-years (QALYs) are the product of the health state utility and the length of time in that state. Data sources for model parameters included Centers for Disease Control and Prevention Active Bacterial Core surveillance, National Hospital Discharge Survey and Nationwide Inpatient Sample data, and data from the National Health Interview Survey. Primary outcome measures were pneumococcal disease cases prevented and incremental costs per QALY gained.

With no vaccination, lifetime risk for hospitalized NPP from 50 years of age onward was 9.3%. For IPD, lifetime risk was 0.86%, and for death due to pneumococcal disease, lifetime risk was 1.8%. Among the cohort of approximately 4.3 million 50-year-olds in the United States in 2006, the model estimated 396,087 NPP hospitalizations, 36,576 IPD cases, and 75,647 deaths due to pneumococcal disease over their lifetime.

As for the public health effect of different strategies, those that used PPSV23 prevented more IPD than strategies that used PCV13 only, while strategies using 2 scheduled PCV13 doses prevented more NPP. In the worst-case scenario NPP analysis, more total pneumococcal disease cases and deaths were prevented by strategies containing PCV13 compared with the current PPSV23 recommendation strategy.

In general, interventions costing <$20,000 per QALY gained show strong evidence for adoption, interventions costing $20,000 to $100,000 per QALY have moderate evidence, and those costing >$100,000 per QALY have weaker evidence for adoption. In the base-case scenario, administration of PCV13 as a substitute for PPSV23 in current recommendations cost $28,900 per QALY gained compared with no vaccination and was more cost-effective than the currently recommended PPSV23 strategy.

Routine PCV13 at ages 50 and 65 years cost $45,100 per QALY compared with PCV13 substituted in current recommendations. Adding PPSV23 at age 75 years to PCV13 at ages 50 and 65 years gained 0.00002 QALYs, costing $496,000 per QALY gained. When PCV13 effectiveness against NPP is set at low-range estimates, current PPSV23 recommendations were favored, costing $34,600 per QALY gained.

The authors contend that adults should be vaccinated with PCV13 rather than PPSV23 and suggest that PCV13 administered either as a substitute for PPSV23 in current recommendations or routinely at ages 50 and 65 years might reduce pneumococcal disease burden in an economically reasonable fashion.

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