Economic analysis of pandemic influenza vaccination strategies in Singapore.
BACKGROUND
All influenza pandemic plans advocate pandemic vaccination. However, few studies have evaluated the cost-effectiveness of different vaccination strategies. This paper compares the economic outcomes of vaccination compared with treatment with antiviral agents alone, in Singapore.


METHODS
We analyzed the economic outcomes of pandemic vaccination (immediate vaccination and vaccine stockpiling) compared with treatment-only in Singapore using a decision-based model to perform cost-benefit and cost-effectiveness analyses. We also explored the annual insurance premium (willingness to pay) depending on the perceived risk of the next pandemic occurring.


RESULTS
The treatment-only strategy resulted in 690 deaths, 13,950 hospitalization days, and economic cost of USD$497 million. For immediate vaccination, at vaccine effectiveness of >55%, vaccination was cost-beneficial over treatment-only. Vaccine stockpiling is not cost-effective in most scenarios even with 100% vaccine effectiveness. The annual insurance premium was highest with immediate vaccination, and was lower with increased duration to the next pandemic. The premium was also higher with higher vaccine effectiveness, attack rates, and case-fatality rates. Stockpiling with case-fatality rates of 0.4-0.6% would be cost-beneficial if vaccine effectiveness was >80%; while at case-fatality of >5% stockpiling would be cost-beneficial even if vaccine effectiveness was 20%. High-risk sub-groups warrant higher premiums than low-risk sub-groups.


CONCLUSIONS
The actual pandemic vaccine effectiveness and lead time is unknown. Vaccine strategy should be based on perception of severity. Immediate vaccination is most cost-effective, but requires vaccines to be available when required. Vaccine stockpiling as insurance against worst-case scenarios is also cost-effective. Research and development is therefore critical to develop and stockpile cheap, readily available effective vaccines.
Lee
Vernon J
VJ
Center for Health Services Research, National University of Singapore, Singapore, Singapore. vernonljm@hotmail.com
Tok
Mei Yin
MY
Chow
Vincent T
VT
Phua
Kai Hong
KH
Ooi
Eng Eong
EE
Tambyah
Paul A
PA
Chen
Mark I
MI
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D003362:Cost-Benefit Analysis / Q000191:economics; D003661:Decision Support Techniques; D004196:Disease Outbreaks / Q000191:economics*; D006801:Humans; D007252:Influenza Vaccines / Q000191:economics*; D007251:Influenza, Human / Q000191:economics* / Q000401:mortality / Q000517:prevention & control*; D008875:Middle Aged; D018803:Models, Economic; D012846:Singapore; D013045:Species Specificity; D014611:Vaccination / Q000191:economics*
D007252:Influenza Vaccines