US federal agencies on Wednesday approved new booster-dose vaccines targeting the mutated Omicron strain of the Covid-19 pandemic.

The Food and Drug Administration's move streamlines the recipe for shots from Pfizer and rival Moderna that have already saved millions of lives. It is hoped that the updated booster dose will prevent another spike.

US federal agencies on Wednesday approved their first update to Covid-19 vaccines, with booster doses targeting today's most common Omicron strain.

The Food and Drug Administration's move streamlines the recipe for shots from Pfizer and rival Moderna that have already saved millions of lives. It is hoped that the updated booster dose will prevent another spike.

These updated boosters present us with an opportunity to get ahead” of the next COVID-19 wave said FDA Commissioner Dr Robert Califf.

Although there are many variants of covid, all the vaccines so far have only been against the original virus of covid 19. The new US boosters are a combination of "bivalent" shots. They contain half that original vaccine recipe and half protection against the newest omicron versions, BA.4 and BA.5, which are considered the most contagious yet.

"It really provides the broadest opportunity for protection," said Pfizer vaccine chief Annaliesa Anderson.

The updated boosters are only for people who have already had their primary vaccinations, using the original vaccines. Doses made by Pfizer and its partner BioNTech are for anyone 12 and older while Moderna's updated shots are for adults — if it has been at least two months since their last primary vaccination or their latest booster. They're not to be used for initial vaccinations.