Israel became the first country to begin administering COVID-19 booster shots on Monday after its Health Ministry approved third doses of the vaccine for immunocompromised adults.

The move comes after Pfizer and BioNTech said last week that it will seek authorization from U.S. and European regulators for boosters for their vaccine, an announcement that prompted American health officials to issue a statement saying that fully vaccinated people do not currently need an additional shot. 

Israeli Health Minister Nitzan Horowitz announced Sunday that the country’s health providers have been informed they may begin administering boosters to adults with weakened immune systems. Horowitz said the Health Ministry is evaluating whether to make the additional shots available to the general population.

Israel has fully inoculated 57% of its people, making it the seventh most vaccinated country. But after falling to near zero, new infections, driven by the highly contagious delta variant, have now tripled over the past two weeks to more than 400 a day.

Last week, Israel’s Health Ministry said the Pfizer-BioNTech vaccine was found to be 64% effective against COVID-19 infections, down from 95% in May. The vaccine, however, was 93% effective in preventing serious illness and hospilizations, Israel said.

At a briefing last week, White House press secretary Jen Psaki called the Israeli study “preliminary data," adding: “The vast majority of data from larger assessments and larger studies shows that it is quite effective.”

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases and President Joe Biden’s chief medical adviser, said Monday that the U.S. health officials are analyzing the research, including Pfizer’s, before making a recommendation on boosters in the U.S.

“When you have a regulatory agency like FDA or a public health agency like the CDC, whenever they make solid, official recommendations, they will do that based on solid data — data and evidence that they've gotten from clinical studies — which they are very actively accumulating right now,” Fauci told “CBS This Morning.”

World Health Organization Director-General Tedros Adhanom Ghebreyesus on Monday blasted the idea of wealthier countries offering booster shots while so many poorer nations have vaccinated very few of their people.

“We’re making conscious choices right now not to protect those in most need,” Tedros said. "Currently, data shows us that vaccination offers long-lasting immunity against severe and deadly COVID-19. The priority now must be to vaccinate those who have received no doses and protection."