COST-EFFECTIVENESS OF AN INTERVENTION TO INCREASE VACCINATION RATES IN ADULTS <65 YEARS OLD

Purpose: Vaccination of adults <65 years old is suboptimal. The 4 Pillars Immunization Toolkit to improve adult vaccination rates was tested in a cluster randomized trial; the cost-effectiveness of this intervention is examined here.

Method(s): The 4 Pillars intervention uses primary care practice-chosen components, including immunization standing orders, vaccination access improvements, tracking tools, and a practice immunization champion to improve vaccination rates. This intervention was compared to control in 2 US cities among diverse populations and practices. In <65-year-old adults, 2 vaccines were targeted: influenza and Tdap (tetanus, diphtheria, acellular pertussis). A decision tree model was used to estimate intervention cost-effectiveness compared to control, with outcomes as costs/QALY gained. Trial data supplied changes in vaccination rates and intervention implementation/maintenance costs. US databases and literature data were used to model vaccine effectiveness, illness rates, and costs with/without vaccination over a 10 year time horizon. Future costs and effectiveness were discounted at 3% per year.

Result(s): Total vaccination and illness costs with the intervention (cost $1.78 per eligible patient per year), were $46.09 higher compared to control while gaining 0.001 QALYs, or $43,590/QALY gained. The intervention was not favored, at a $100,000/QALY threshold, when varying these influenza-related parameters: yearly attack rate <2.5% (base case 6.6%), case-fatality <0.048% (base 0.134%), influenza vaccine effectiveness <26.2% (base 59%), or program-related absolute increase in influenza vaccination <2.0% (base 8.6%). Results were insensitive to plausible individual variation of all other parameters, including absolute improvement in pertussis vaccination rate (11.8%). In a probabilistic sensitivity analysis, the 4 Pillars intervention was favored in 54.4% of model iterations at a $50,000/QALY acceptability threshold and in 90.8% at $100,000/QALY. In a separate scenario analysis, the intervention became cost saving if the total economic burden of influenza was >$1967 per case (base $265).

Conclusion(s): The 4 Pillars Immunization Toolkit was an economically reasonable intervention to improve vaccination rates in adults <65 years old.