Jo Walker is a scientist, but rather than use the reported vaccine efficacy (90-100%), Jo’s model used an estimate of 70%.

Jo's model also doesn't take into account the highly age-stratified risk of COVID published by the CDC. The CDC says the risk of death is 270x higher for 70+ as those aged 18-50. Jo’s model ignored the highly lethal nature of this disease to the elderly, so Jo was able to recommend that younger essential workers be prioritized above the elderly, because the elderly are whiter.

The NYT explained why this was fair, and now many states are implementing vaccination plans based on Jo’s model—resulting in hardly anyone over 70 being vaccinated.