The U.S. Food and Drug Administration panel on Friday endorsed a booster shot of the Johnson & Johnson COVID-19 vaccine, according to the Associated Press.  

The panel cited concerns that Americans who got one shot are not as protected as those who received two shots. Additionally, J&J said the additional dose adds more protection against the deadly coronavirus.  

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According to AP, the FDA’s panel voted unanimously in support of the booster being given two months after immunization. A number of experts believe it makes sense to think of the J&J vaccine as a two-dose vaccine. 

“I think this frankly was always a two-dose vaccine,” said FDA adviser Dr. Paul Offit. “It would be hard to recommend this as a single-dose vaccine at this point.” 

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According to the CDC, the J&J, Pfizer and Moderna vaccines have been shown to protect against death and hospitalizations that can occur from COVID-19. The primary goal is to give the first shots to those who haven’t been vaccinated, as 66% of Americans have received a vaccine, according to The New York Times. 

What makes this situation more urgent is that in several studies J&J’s vaccine has shown lower effectiveness, AP reported. Also, there have been reported breakthrough infections involving those who are fully vaccinated because of the delta variant. 

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“This is really — with the second dose — bringing it, I think, on par with those other vaccines in terms of effectiveness,” Dr. Archana Chatterjee of Rosalind Franklin University told AP.