Look at the difference in vaccine priorities between the UK and US.
Deaths from COVID-19 are heavily weighted by age, vaccinating those over 70 will drop the death toll dramatically with relatively few vaccinations. With few exceptions, early vaccinations for people under 50 won't prevent many deaths.
The UK goes with these tiers:
Care home patients, their caregivers.
Age 80+, front-line health and social workers.
75+, 70+, and the extremely vulnerable.
65+, then younger people with comorbidities.
60, 55, then 50+
The top 3 lines will cut their death toll more than 50%, with relatively few vaccinations. By late January, they'll be in much better shape.
In the US, by contrast, look who gets vaccinated before a 70-year old with a comorbidity:
Healthcare workers doing non-COVID facing work, all police, fire and emergency workers, all pre-K and K-12 workers, and workers in transit, grocery, agriculture, food, sanitation or public works.
That's a huge chunk of the population, which means the people most likely to die will be denied vaccines until April or later.
Reading the UK list, it's perfectly clear what their goal is - protect the most vulnerable. Reading the US list...it's not at all clear what our goals are.