Dr. Fauci says a third booster shot for COVID-19 ‘might likely happen’ for people who are immunocompromised

• On CNN Sunday morning, Dr. Anthony Fauci said a COVID-19 vaccine booster shot "might likely happen."
• Emerging data from Israel indicates that the two-shot Pfizer vaccine could be less effective against the Delta variant.
• As Delta causes a surge in cases, Fauci said the coronavirus outbreak is now "a pandemic among the unvaccinated."
• See more stories on Insider's business page.

Dr. Anthony Fauci, the nation's infectious disease expert and President Biden's chief medical advisor, says that a third COVID vaccine booster shot "might likely happen."

On CNN's State of the Union Sunday morning, Fauci told anchor Jake Tapper that the CDC's Advisory Committee on Immunization Practices (ACIP) is looking at evolving data that could recommend a thirdbooster shot, particularly for vulnerable and immunocompromised people.

"It's a work in progress," Fauci said of the CDC's stance on a vaccine booster shot. "It evolves, like in so many other areas of the pandemic. You have got to look at the data."

Fauci said the ACIP is still examining preliminary data from Israel and Pfizer that suggests the Pfizer vaccine could be less effective at protecting against infection from the Delta variant than other variants of the disease.

New data from Israel suggests the Pfizer vaccine was just 39% effective at preventing nationwide infections in late June and early July, while it had been found 95% effective from January to early April, the New York Times reported. However, the vaccine was still over 90% effective at preventing severe infection and hospitalization.

A separate study from the UK indicated that the Pfizer vaccine was still 88% effective against symptomatic Delta infections after two shots.

As to whether or not a booster shot would improve the effectiveness rates, Fauci said that the committee will "continue to look at the data that might push us in that direction."

The Delta variant now makes up about 80% of all new cases in the US, according to CDC data. In the middle of June, the variant made up just 20.6% of the all COVID cases in the US.

Given this current surge in cases, Fauci described COVID-19 as "a pandemic among the unvaccinated," which still accounts for nearly 50% of eligible Americans.

"It's like we have two kinds of America," Fauci said.

Read more: Fauci says fully vaccinated people 'might want to consider' wearing a mask indoors as a precaution against the Delta variant

When asked if people should still wear masks in public, Fauci acknowledged that CDC currently says that those who are fully vaccinated do not need to wear a mask indoors. He added, however, that the Center supports the ability and discretion of local officials to reinstate mask requirements in areas of the country that are experiencing a spike in infections, such as Los Angeles, New Orleans, and Chicago.