(Bloomberg) -- The U.S. Centers for Disease Control and Prevention is now recommending booster shots for all vaccinated people 18 and older as scientists race to study the emerging omicron variant of SARS-CoV-2.

The guidance, which previously said adults “may” get boosters, now says they “should” get a third dose of the Moderna Inc. or Pfizer Inc. shot six months after their second dose. The same recommendation applies to those who received the single-shot Johnson & Johnson vaccine but after only two months.

Earlier this month, the CDC signed off on recommendations that all people 50 and over should get a booster shot, as well as adults 18-64 with underlying medical conditions or who work or have living situations that make them more likely to develop severe Covid-19. 

QuickTake: What we know about omicron, the new virus variant

Rochelle Walensky, head of the CDC, said early data from South Africa suggest that the omicron variant has increased the transmissibility of the virus and that scientists are urgently examining vaccine effectiveness related to the mutation. Pfizer partner BioNTech SE, Moderna and J&J are working to adapt their vaccines to address the omicron variant.

Walensky also said that the emergence of omicron further emphasizes the importance of vaccination, boosters and other measures to protect against the virus. She also encouraged people to get a Covid test if they are sick.

“Increased testing will help us identify omicron quickly,” Walensky said in a statement.

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