Decision Analysis Modeling Favors Optimal Influenza Vaccination in Late November or Early December
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Background
Waning vaccine protection and variable epidemic timing create a tradeoff between vaccinating before influenza circulation and preserving protection when disease burden is greatest. Existing guidance does not quantify the week that best balances this tradeoff.
Objective
To estimate the optimal week for influenza vaccination while accounting for uncertainty in epidemic timing and vaccine protection.
Design
Simulation-based probabilistic decision analysis.
Setting
United States outpatient influenza surveillance from the 50 states and District of Columbia during the 2010/11 through 2018/19 and 2023/24 through 2025/26 seasons.
Participants
People in the United States who would receive 1 influenza vaccine dose.
Interventions
Vaccination during Morbidity and Mortality Weekly Report (MMWR) weeks 36 through 12.
Measurements
We combined influenza-like illness (ILI) syndromic surveillance and influenza-specific data with uncertainty in epidemic timing, initial vaccine effectiveness, waning, and immune-response lag. For each candidate week, the model estimated direct protection against outpatient surveillance burden.
Results
The primary model identified the optimal time to vaccinate as week 47, with weeks 47–48 being of similar utility. Our influenza-weighted outpatient analysis (ILI+) selected week 48. Compared with week 44, near the end of the current September–October guidance window, week 48 reduced modeled influenza-weighted outpatient burden by 50 visit equivalents per 10,000 weekly encounters.
Limitations
The model assumed vaccination would occur, used outpatient surveillance burden rather than severe outcomes, and did not incorporate transmission effects.
Conclusion
Under the primary waning model, these findings favor vaccinating during weeks 47–48, approximately late November through early December, for most one-dose recipients.
Primary Funding Source
None.
