According to a computer-based cost-effectiveness analysis in the February issue of JAMA, recommending the use of the 13-valent pneumococcal conjugate vaccine (PCV13) could possibly prevent more pneumococcal disease than the current 23-valent pneumococcal polysaccharide vaccine (PPSV23) recommendations. The costs would remain reasonably economic, however the researchers point out that their findings are sensitive to several assumptions.

The article’s background information states that the PPSV23 vaccine has been recommended to prevent invasive pneumococcal disease (IPD) in adults since 1983, saying:

“Most studies show that PPSV23 provides some protection against IPD, but studies have reached contradictory conclusions about its ability to prevent nonbacteremic pneumococcal pneumonia (NPP), which causes several hundred thousand illnesses annually in the United States.”

The authors continue to say that the efficacy of the PCV13 vaccine to prevent NPP in adults remains unknown. The Food and Drug Administration has recently approved PCV13 for use amongst adults aged 50 years and older, however, the vaccine’s cost-effectiveness in comparison with PPSV23 amongst U.S. adults is not known.

Kenneth J. Smith, M.D., M.S., of the University of Pittsburgh School of Medicine and his team decided to estimate the efficacy and cost-effectiveness of pneumococcal vaccination strategies amongst adults aged 50 years and older by using various modeling techniques and simulations in hypothetical groups of American 50-year-olds.

An expert panel developed vaccination strategies and efficacy estimates of the indirect (herd immunity) impact of childhood PCV13 vaccination, which they projected based on observed 7-valent pneumococcal conjugate vaccine (PCV7) effects based on data sources obtained from the Centers for Disease Control and Prevention Active Bacterial Core surveillance, the National Hospital Discharge Survey and Nationwide Inpatient Sample data, and the National Health Interview Survey.

The findings revealed that no vaccination produced an estimated lifetime risk for hospitalized NPP of 9.3% for those aged 50 years or older, 0.86% for IPD, and 1.8% for deaths caused by pneumococcal disease.

A comparison of all the different vaccination strategies in the analysis revealed that those using PPSV23 were estimated to prevent more IPD as compared with strategies using only PCV13, whilst those with 2 scheduled PCV13 doses were estimated to prevent more NPP.

The base case scenario shows that in terms of cost-effectiveness, administering PCV13 as a substitute for PPSV23 in present recommendations, i.e. vaccinating those aged 65 years and younger if co-existing illnesses are present, were estimated to cost $28,900 per quality-adjusted life-year (QALY) gained in comparison with no vaccination.

This makes PCV13 more cost-effective compared with the currently recommended PPSV23 strategy. Routine vaccinations at the ages of 50 and 65 years were estimated to cost $45,100 per QALY for PCV13 as compared with PCV13 substituted in current recommendations, whilst estimations showed that administering PCV13 at 50 and 65 years followed by PPSV23 at 75 years cost $496,000 per QALY gained.

The researchers comment:

“There are no absolute criteria for cost-effectiveness, but in general, interventions costing less than $20,000 per QALY gained are felt to have strong evidence for adoption, interventions costing $20,000 to $100,000 per QALY have moderate evidence, and those costing more than $100,000 per QALY have weaker evidence for adoption.”

They highlight that whilst their results were robust in sensitivity analyses and alternative scenarios, they were not when assuming low PCV13 efficacy against nonbacteremic pneumococcal pneumonia, or when greater childhood vaccination indirect effects were modeled. In these circumstances PPSV23 as currently recommended turned to be in favor.

They conclude:

“Model estimates of the effect of adult PCV13 would be strengthened by evidence of PCV13 effectiveness against NPP from ongoing clinical trials and availability of data on the indirect effects of childhood PCV13 on adult pneumococcal disease rates.”

Eugene D. Shapiro, M.D., of the Yale University School of Medicine and Yale Graduate School of Arts and Sciences, New Haven, Conn., writes in a linked editorial that policy makers will probably need do decide whether they recommend changing the immunization strategy of adults in the absence of definitive data on all values that contribute to analysis of the potential cost-effectiveness of a change in policy, stating:

“The analyses by Smith et al provide a reasonable framework with which to approach this issue. However, if recommendations are made to switch to PCV13 for adults, the degree to which subsequent decreases in rates of both invasive pneumococcal infections and NPP among adults are due to a switch to PCV13 for adults or to the already implemented administration of PCV13 to children might never be known.

What does seem clear is that improvements in vaccines against pneumococci and increased rates of immunization likely will result in continued reductions in the incidence of infections due to this common pathogen.”

Written by Petra Rattue