U.S. health officials are now reviewing the possible need for a third COVID-19 for adults who have already completed the two-shot regimen after meeting with Pfizer officials earlier this week. 

“We’re keenly interested in knowing whether or not a third dose may be associated with any higher risk of adverse reactions, particularly some of those more severe — although very rare — side effects,” said Jay Butler, deputy director at the U.S. Centers for Disease Control and Prevention, during a media briefing Tuesday.

Though a decision hasn’t been made, Butler said the federal government specifically sees that booster shots, if deemed necessary, would be most needed for the elderly, including nursing home residents, and groups at higher risk of severe infection. 

He added that health officials have yet to see any evidence of decreasing immunity among adults fully vaccinated against COVID-19. 

The news of the review comes after federal health officials last week said a booster shot is not needed for vaccinated people, asserting the effectiveness of currently available COVID-19 vaccines. 

Drugmaker Pfizer, however, has warned the federal government that nursing homes could be at risk of future COVID outbreaks if officials wait too long to administer a third round of shots.

Consumer advocates have warned that long-term care facilities should start equipping themselves for the distribution of booster shots even before an official announcement would be made.

“Nursing homes should absolutely be planning for booster shots, if those become medically necessary and appropriate,” Toby Edelman, senior policy attorney for the Center for Medicare Advocacy, said in late May. “The COVID-19 pandemic made clear the critical importance of facility leadership anticipating and planning for contingencies.”