WFLA

Why eight months? What’s behind the timing of the COVID booster shot

FILE - A pharmacy technician loads a syringe with Pfizer's COVID-19 vaccine, Tuesday, March 2, 2021, at a mass vaccination site at the Portland Expo in Portland, Maine. U.S. experts are expected to recommend COVID-19 vaccine boosters for all Americans, regardless of age, eight months after they received their second dose of the shot, to ensure lasting protection against the coronavirus as the delta variant spreads across the country. An announcement was expected as soon as this week, with doses beginning to be administered widely once the Food and Drug Administration formally approves the vaccines. (AP Photo/Robert F. Bukaty)

(NBC) — Federal health officials are expected Wednesday to present evidence for why people are likely to need COVID-19 boosters eight months after their second doses of a vaccine, according to sources with the Centers for Disease Control and Prevention.

The eight-month time frame is most likely based on findings from both the U.S. and abroad looking at how the vaccines have held up over time — and whether they can stand up to the hypertransmissible delta variant of the coronavirus that has overtaken the country.

“Delta is forcing this discussion” on boosters, said Dr. Colleen Kraft, associate chief medical officer at Emory University Hospital in Atlanta.

The variant now accounts for nearly 100 percent of new Covid-19 cases in the U.S., according to the CDC. The seven-day average of Covid-19 cases has soared by 700 percent since the beginning of July, when delta became the dominant strain in the U.S.

Read the full story on NBCNews.com.