Evidence shows that by fall 2021, COVID‑19 booster doses were indeed being recommended and deployed for parts of the vaccinated population in both Israel and the U.S., matching Friedberg’s prediction.

Key timeline points:

• Israel:

  • On July 30, 2021, Israel began offering a third (booster) dose of the Pfizer-BioNTech vaccine to people aged 60 and older who had been vaccinated at least five months earlier. This is widely reported as the first national booster campaign.
  • This clearly satisfies “by fall 2021” and “for at least some portion of the vaccinated population.”

• United States (CDC / FDA):

  • On August 12, 2021, the FDA amended the EUA for Pfizer and Moderna vaccines to allow an additional dose for certain immunocompromised people.
  • In September 2021, U.S. health authorities moved more broadly: the FDA and CDC authorized and recommended Pfizer-BioNTech booster doses for specific groups (e.g., older adults, people with underlying conditions, and those at high risk due to occupational exposure).
  • These actions are explicit recommendations and led to active deployment of boosters in the U.S. during fall 2021.

Given that:

• the prediction was made on July 9, 2021;
• boosters were recommended and rolled out in multiple countries (notably Israel and the U.S.) before and during fall 2021;
• and the prediction’s condition (“for at least some portion of the vaccinated population”) is clearly met,

Result: The prediction is right.