A back-of-the-envelope timeline for U.S. Covid-19 vaccinations
Dr. Bob Wachter, Chair of the Department of Medicine at UCSF, has emerged as one of the nation's most informative and accessible health experts on Covid—summarizing the latest research, data, and news via his near-daily tweet storms.
For his tweets and insights, Dr. Wachter has been featured in nationwide news outlets including The Wall Street Journal, NPR, CNN, and The New York Times. Give this man a Pulitzer Prize.

He recently tweeted a back-of-the-envelope prediction of a possible 2021 vaccination timeline in the U.S., and we wanted to share his estimates with you.
This model is based on the CDC's recommendations for which groups would receive the vaccine first—once it's approved and available. This also factors in a potential ramp-up schedule for vaccine production, according to statements made by officials at Pfizer, Moderna, and Operation Warp Speed.
The 3 key dates and milestones highlighted:
- May 2021: Vaccination complete of phase 1 group, which includes healthcare workers, people >65 in nursing homes, people >65 w/ pre-existing conditions, essential workers (144M people)
- September 2021: Herd-immunity threshold reached, ~70% vaccinated (230M people)
- January 2022: All U.S. population vaccinated (329M people)

During a time when the U.S. is reaching record levels of daily coronavirus cases, hospitalizations, and deaths, this timeline provided us with some sense of relief, clarity, and hope. There is a light at the end of the tunnel...
Read Dr. Wachter's full tweet storm for more details, including some potential obstacles he sees that could get in the way. The most concerning on the list, of course, are politics and misinformation—but luckily, we'll have Dr. Wachter to help us fight against these forces.
5/ And here’s my estimate of how many people in U.S. can be vaccinated at various times in 2021. It’s based on statements made by @Pfizer, @moderna_tx & Op Warp Speed, and assumes we have enough vaccine to vaccinate 20M by Jan 2021, 150M by June, & the entire country by December. pic.twitter.com/3zL6xu34Il
— Bob Wachter (@Bob_Wachter) December 2, 2020