US health experts say most people don't need a COVID-19 booster shot -- yet.

But all three companies, which make the vaccines being used in the US, are studying whether, and when, they might be. The CEO of Pfizer says it appears a booster will be needed between eight and 12 months.

Israel began offering boosters for people over 50, after seeing the effectiveness of Pfizer's vaccine drop to only 64% against the Delta variant.

The decision on whether to offer Covid-19 boosters in the US will involve the Food and Drug Administration and the Centers for Disease Control, and the process will depend on whether the booster is the same as the vaccines already approved, or a modified version.

Pfizer is working on one targeting the Delta variant; its approval process could be similar to what happens with flu vaccines each year.

The White House is expected to lay out a booster plan for all vaccinated Americans in September.

Dr. Anthony Fauci, Chief Medical Adviser to US President Joe Biden, says eventually, everyone will likely need a booster shot, but it's too early to be certain.