Discussion: What factors are impacting the vaccine rollout and distribution?

The vaccine rollout has offered new hope in seeing light at the end of the COVID-19 pandemic tunnel for many Americans. However, there have been conflicting timelines around when most Americans will be vaccinated. Currently, one factor contributing to vaccination delays is the winter weather storm in Texas which is impacting shipments. What do you think are the main factors impacting the vaccine rollout and distribution? Listed below are some relevant articles:

https://www.nytimes.com/interactive/2020/us/covid-19-vaccine-doses.html - NY Times

https://www.wsj.com/articles/behind-americas-botched-vaccination-rollout-fragmented-communication-misallocated-supply-11613663012 - Wall Street Journal

https://www.washingtonpost.com/health/2021/02/16/covid-vaccine-winter-storm/ - The Washington Post