Thread by @InfectiousDz

So what do we know about the Pfizer vaccine.

1. Great news: vaccine, so far, 90% effective in reducing symptomatic COVID, as opposed to saline injection

2. Study enrolled 43,538 volunteers and 38,955 had 2 doses; 94 cases in unvaccinated
statnews.com/2020/11/09/cov…

3. Interim analysis found 94 cases in the non-vaccinated sooner than 1st expected. Surges in cases will mean more potential cases and faster vaccine study results

4. Authorization process will not begin in US until 2 months after 2nd doses given. Likely late Nov.

5. Phase 3 trial still on-going, will need over 164 cases for final analysis, which given recent surges will likely coincide with the 2 months after 2nd dose time period.

6. No mRNA vaccine has been approved in any country ever, though such vaccines have been studied for years

7. Logistics of distribution to reach herd immunity will be complicated. Pfizer vaccine will require 2 doses. It will need to be stored in neg 80C sub zero fridges.

8. If the vaccine is authorized for use, doses will be limited. 50M planned by end of 2020, 1.3B in 2021

9. Many countries already pre-ordered the vaccine - EU, US, UK, Canada, Australia. These orders exceed the stock available in 2020. UK alone has ordered 30M. Countries outside initial purchasing groups will have difficulty obtaining the vaccine, besides sub zero fridge logistics

10. Vaccine studied around world (Argentina, Brazil, Germany, South Africa, US), will need to ensure diversity

11. Vaccine studied in adolescents and older adults (65-85). Early data showed older adults hadgreater neutralizing antibody response w/vaccine than natural infection

12. Still waiting for data on safety, side effects, and longterm durability and effectiveness of the vaccine. Early work showed side effects included standard findings - pain at the injection site and fatigue, chills and fever

13. What may matter most in some parts of the world may be trust in the vaccine, rather than just enough doses.

Note among African Americans surveyed, 32% said they would definitely/probably take a vaccine if available today.
pewresearch.org/science/2020/0…

US population 331 million.
To achieve herd immunity with 2 doses, even with 90% efficacy and some natural immunity, this will require a lot of vaccines.
Vaccination of 80% of population = 530 shots
The annual flu vaccination has reached 140-170 shots/year
cdc.gov/flu/prevent/va…

14. Longer term data is needed to better understand how long vaccine immunity will last. It's possible that 2 shot vaccination will need to be followed by regular boosters, complicating control and logistics even more.