BioNTech SE, Moderna Inc. and Johnson & Johnson are working to adapt their COVID-19 vaccines to address the omicron variant, with the German partner of Pfizer Inc. saying it could have a new version ready within 100 days if necessary.

BioNTech said Monday that it has started development in order to move as quickly as possible. The first steps of developing a new vaccine overlap with the research necessary in order to evaluate whether the shot will be needed — a process that both it and Moderna began last Thursday as news of the new variant began to spread around the world. 

Drugmakers have been preparing for months for the possibility of needing to tweak their vaccines to deal with a new variant. BioNTech, Pfizer and Moderna will be able to move at unprecedented speed: both vaccines use messenger RNA technology, which shortens the timeline for a new shot to only a few months. 

J&J’s vaccine relies on a different technology called a viral vector. The company said it’s testing immune blood components from participants in trials of its booster to look for responses to omicron and is pursuing a vaccine that specifically targets the variant that it will take into human studies if needed. 

Omicron has raised concerns around the world, with countries implementing travel bans to buy time as researchers race to study whether it will evade vaccines and spread more rapidly. Understanding the new strain will probably take several weeks, according to scientists. 

BioNTech and Moderna have each said that it should become clear within weeks whether they’d need to adjust their shots. Pfizer and its partner put plans in place months ago to be able to ship a new version of their shot within 100 days if necessary, according to a spokeswoman.

It’s standard procedure to begin developing an updated vaccine in parallel with running tests of how the new strain reacts with the existing shot “in order not to waste any time,” BioNTech said. “Lab tests will deliver more information on whether or not adaptation of the vaccine will be necessary.” 

Vaccinated people should still be protected, depending on how long ago they got their shots, and for now the best advice is to take one of the current Covid vaccines, Moderna Chief Medical Officer Paul Burton said on Sunday on the BBC’s “Andrew Marr Show.” 

Pfizer’s and BioNTech’s vaccine is on track to be the best-selling pharma product ever on a yearly basis. Another vaccine maker, AstraZeneca Plc, said Friday it’s also investigating the variant.