Flu vaccine risk-benefit calculator

Quantify the mortality trade-off of seasonal influenza vaccination in micromorts (μmort) — one-in-a-million chances of death. Adjust all parameters below; the chart updates live.

This calculator is for educational purposes only and does not constitute medical advice. Only mortality risk is modeled — morbidity outcomes (hospitalization, long recovery, post-influenza complications) are not included and would further favor vaccination. Individual risk factors (immunocompromised status, egg allergy, prior GBS) are not modeled. Indirect benefits (herd immunity, reduced transmission to vulnerable contacts) are not included. Consult your physician. See methodology and limitations.

How to read this: The net benefit is the number of micromorts (one-in-a-million chances of death) prevented by vaccination — accounting for both the mortality avoided (from flu death and flu-triggered GBS) and the mortality risk added (from vaccine-triggered GBS and anaphylaxis). A positive value means vaccination reduces your expected mortality risk. All values are annual and per-person. Indirect benefits (herd immunity) are not modeled.
Net benefit by age (micromorts)
Summary for age
2.19
net benefit (μmort saved)
$21.91
net benefit (monetary value)
2.27
μmort avoided (upside)
0.0763
μmort incurred (downside)
5.6
μmort from flu (unvaccinated)

Parameters

Influenza infection risk (% per year, unvaccinated) Source
%
%
%
%
Case fatality rate (% of symptomatic infections) Source
%
%
%
%
Vaccine effectiveness Source
%
Note: VE is often substantially lower in the elderly (sometimes 20–30%). Since ages 65+ account for the vast majority of flu deaths, consider lowering VE when evaluating older ages.
Guillain-Barré syndrome Source
per M doses
%
per M infections
Anaphylaxis Source
per M doses
%
Value of a Statistical Life Source
M USD
1 micromort ≈ $10 at this VSL. US EPA base estimate is $7.4M (2006 dollars), ~$11M inflation-adjusted; DOT uses ~$12.5M.
Methodology

This is a single-season, per-person expected-mortality model expressed in micromorts (μmort).

Benefit (micromorts avoided by vaccinating):

  • Direct influenza mortality avoided: P(symptomatic flu) × CFR(death | symptomatic flu) × VE × 106
  • Flu-triggered GBS deaths avoided: P(symptomatic flu) × (GBS per 106 infections) × GBS-CFR × VE

Risk (micromorts incurred by vaccinating):

  • Vaccine-triggered GBS micromorts: (GBS per 106 doses) × GBS-CFR
  • Anaphylaxis micromorts: (anaphylaxis per 106 doses) × anaphylaxis-CFR

Net benefit = Benefit − Risk

Monetary value = Net benefit × VSL (since 1 μmort = $1 per $1M of VSL).

Simplifications & caveats:

  • CFR, not IFR. The model uses case fatality rates (deaths per symptomatic infection) multiplied by the symptomatic infection rate. Not all infections are symptomatic, so this may somewhat overestimate mortality compared to an IFR-based approach — though it also excludes asymptomatic infections from the denominator, so the two biases partially cancel.
  • Denominator mismatch risk. The GBS-from-flu input is entered as “per million infections”, but published estimates may be reported per infection, per symptomatic illness, or per medically attended influenza/ILI. If the source denominator differs from the infection-risk input on this page, the GBS component can be under- or over-stated.
  • Single-year static model. The calculation ignores prior immunity (from past infection or vaccination) and does not accumulate risk over multiple seasons. In reality, cumulative lifetime benefit of annual vaccination is more nuanced than simply multiplying the single-year figure.
  • No age stratification for some parameters. VE, vaccine adverse event rates, and adverse-event CFRs are treated as constant across ages even though they can vary (often materially) by age and health status.
  • Only mortality is modeled. Non-fatal outcomes (hospitalization, prolonged recovery, post-infectious complications) and indirect effects (reduced transmission to others) are excluded; including them would generally increase the estimated benefit of vaccination.

Key sources: CDC Flu Burden, Kwong et al. 2013 (GBS), Osterholm et al. 2012 (VE), van den Berg et al. 2014 (GBS CFR), McNeil et al. 2016 (anaphylaxis).

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