Original title: Decision Analysis Modeling Favors Optimal Influenza Vaccination in Late November or Early December
Austin Meyer, Brittany Rosales, Shihao Yang, Mauricio Santillana · September 2026
Flu shots present a tough timing puzzle. If you get vaccinated too early, your protection fades before the worst part of flu season hits. If you wait too long, you might catch the virus before the shot kicks in. Current health advice does not name the single best week to get vaccinated. To find out, researchers built a computer simulation using United States outpatient flu tracking data. The model factored in how fast protection wears off, how long the immune system takes to respond, and changing epidemic timing. It found that the best time to vaccinate is week 47 or 48, which falls in late November or early December. Waiting until week 48 instead of week 44—near the end of the current September to October recommendation—cut the modeled flu outpatient burden by 50 visit equivalents per 10,000 weekly encounters.
Imagine you're cooking a dish that tastes best served right away, but you don't know exactly when your guests will arrive. Cook it too early and it dries out; cook it too late and everyone is hungry. In this paper, the dish is the flu shot, the guests are the flu season, and the model calculates the best time to start cooking so the dish is at its best when people actually show up.
Most flu shots happen in September or October, but this model says waiting until late November or early December would prevent more outpatient illness. That could push public health guidance later and help people get more protection from the same vaccine.
The model assumes everyone gets vaccinated, so it doesn't address whether later timing reduces uptake. It measures outpatient visits, not hospitalizations or deaths, so severe outcomes aren't directly captured. It also ignores transmission — how vaccinating some people protects others. The results depend on the waning model used; a different waning assumption could shift the optimal week.
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Decision Analysis Modeling Favors Optimal Influenza Vaccination in Late November or Early December — Austin Meyer, Brittany Rosales, Shihao Yang et al. — medRxiv — doi:10.64898/2026.09.11.26362843
Abstract licence: CC BY
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.