HealthDay News — Vaccinating adults with the 13-valent pneumococcal conjugate vaccine (PCV13, Prevnar 13, Wyeth), now only used in children, instead of the currently recommended 23-valent pneumococcal polysaccharide vaccine (PPSV23, Pneumovax 23, Merk) has the potential to prevent more disease at a better price, results of a modeling study suggest.

The estimated cost per quality life-year gained with PCV13 was $28,900 compared with $34,600 for PPSV23, Kenneth J. Smith, MD, of the University of Pittsburgh, and colleagues reported in the Journal of the American Medical Association.

“PCV13 might prevent more pneumococcal disease compared with current PPSV23 vaccination recommendations while remaining economically reasonable,” the researchers wrote.

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PCV13 covers the 13 bacterial serotypes that account for the most invasive forms of pneumonia. The vaccine replaced the 7-valent pneumococcal conjugate vaccine (PCV7) used for children in 2010 and gained expanded indications for adults aged 50 and older in Jan. 2012.

Using hypothetical cohorts of U.S. adults aged 50 years, Smith and colleagues developed vaccination strategies and effectiveness models and performed cost analyses.  As part of these models, the researchers extrapolated data on the indirect effects of herd immunity observed with another conjugate vaccine, PCV7.

PPSV23, although offering protection against a greater number of pneumococcal serotypes than PCV13, does not have much effectiveness against nonbacteremia cases of pneumonia. Based on efficacy data from PCV7, the researchers hypothesized that PCV13 may have more efficacy in preventing pneumonia cases that do not involve the bloodstream infections.

But if this assumption does not hold true, neither will the favorable cost-benefit findings. If PCV13 has low effectiveness against nonbacteremic pneumonia it would cost $131,000 per quality life-year gained compared with $34,600 for the 23-valent vaccine. In this case, current recommendations of PPSV23 were favored.

In an accompanying editorial, Eugene D. Shapiro, MD, of Yale University, pointed out that another unknown modeling variable — the level of herd immunity conferred — could also determine whether PCV13 or PPSV23 is more cost effective. Not enough data is currently available to show how sizable the herd immunity effect from children vaccinated with PCV13 will be in adults, he wrote.

A randomized clinical trial assessing PCV13 in 85,000 adults aged 65 years and older is currently underway in the Netherlands with results expected to be available in 2013.

Smith KJ et al. JAMA. 2012; 307: 804-812.

Shapiro ED. JAMA. 2012; 307: 847-849.