LONDON — As the new omicron Covid variant spreads around the world, hopes are being pinned on vaccine makers’ ability to develop effective shots against the strain.

Global market sentiment nosedived on Tuesday morning amid fears that the Covid-19 vaccine currently in use could be less effective against the new omicron variant. The strain was first identified in South Africa and designated a “variant of concern” by the World Health Organization on Friday.

The sharp reversal for European and U.S. stock futures came after Moderna CEO Stephane Bancel told the Financial Times that he expects existing vaccines to be less effective against the new variant.

Bancel told CNBC on Monday that it could take months to develop and ship a vaccine that specifically targets the omicron variant. He added that will take at least two weeks to determine how much the mutations have impacted the efficacy of the vaccines currently on the market.

Read more: Omicron poses “very high” global risk, world must prepare -WHO

The omicron variant has more than 30 mutations on the spike protein that binds to human cells. Some of the mutations are associated with higher transmission and a decrease in antibody protection, according to the WHO.

The UN health agency reiterated on Monday that there are still considerable uncertainties and unknowns regarding this variant, however.

First of all, experts don’t yet know just how transmissible the variant is and whether any increase in infections is because it can escape prior immunity or because it is more transmissible. Secondly, there is uncertainty over how well vaccines protect against infection, transmission, severity of illness and death when it comes to the omicron. And thirdly, it is unknown whether the variant causes more severe symptoms.

The WHO has said it will take weeks to understand how the variant may affect diagnostics, therapeutics and vaccines.

Tweaks

The world now faces an anxious waiting game as experts strive to discover what challenges and risks the omicron variant poses.

Any new variant is closely examined to see whether current vaccines are effective against it — if not, vaccines will need to be tweaked to target the new strain. The Covid vaccine makers are confident they can do this, but it will take time to develop, test, manufacture and deploy these new shots to hundreds millions of people.

Pfizer’s CEO Albert Bourla said the impact of omicron on its own two-dose vaccine — which was developed with German biotech BioNTech and has been widely deployed in the U.S. and Europe — remains to be seen.

“I don’t think that the result will be the vaccines don’t protect,” Bourla told CNBC on Monday, adding, “I think the result could be, which we don’t know yet, the vaccines protect less.”

A booster dose of an authorized vaccine is currently the only way to bolster waning immunity against Covid-19, but vaccine producers are also looking at developing shots specifically targeting the omicron variant.

Bourla said Pfizer had already begun work on a new vaccine if necessary. The company made its first DNA template on Friday, he said — the initial step in the development process of a new vaccine.

Pfizer and BioNTech also said last week that they are investigating omicron, first labeled B.1.1.529, and can adapt their vaccine quickly if needed.

“We have made multiple times clear that we would be able to have the vaccine in less than 100 days,” Bourla said. He noted that the company was able to create vaccines for the beta and delta variants quickly, though they ultimately weren’t used because the original shots remained effective.

Read more: South Africa delays COVID vaccine deliveries as inoculations slow

Moderna said last week that it was testing three existing Covid booster candidates against the omicron variant and would also create a new omicron-specific vaccine candidate. 

Both Moderna and Pfizer-BioNTech’s shots are messenger RNA (mRNA) vaccines which teach our cells how to make a protein that will trigger an immune response in our bodies. This response then produces antibodies that help to protect people against Covid infection.

Johnson & Johnson and AstraZeneca have also produced widely available and effective Covid-19 vaccines (although the AstraZeneca shot is not yet authorized in the U.S.), but their shots are known as “viral vector” vaccines.

This type uses a modified version of a virus (a vector) to deliver genetic instructions to the body’s cells. The cells then produce harmless pieces of the virus called antigens which trigger an immune response in the body. If you are exposed to the real virus later, your immune system will recognize it and know how to fight it.

Both Johnson & Johnson and AstraZeneca have said they are investigating and testing the new variant.

Rafael Bayarri Olmos, a researcher at the Copenhagen University Hospital, told CNBC on Tuesday that variants are “taking a toll” on how well Covid vaccines can prevent infection.

“Now we have omicron that has 32 mutations in the spike protein, some of them have been seen before and they are concerning — they can make the virus more transmissible, they can make them better at avoiding immune recognition, or avoiding your defenses — so we do expect that the vaccines won’t be so, so effective but that doesn’t mean they are not going to work,” he added.

“They are one of our best tools now to curb the spread of this virus.”

Omicron risks

Omicron has now been found in more than a dozen countries, causing many to impose travel restrictions and implement tighter Covid measures, such as compulsory mask-wearing and advising people to work from home.

It comes as many countries are already dealing with high daily infections due to the delta variant, which is globally dominant.

Covid symptoms linked to the omicron variant have been described as “extremely mild” by the South African doctor who first spotted the new strain. Nonetheless, the World Health Organization warned Monday that the omicron variant is likely to spread further and poses a “very high” global risk.

Francois Balloux, director of UCL Genetics Institute at University College London, stressed that very little is known about how contagious and deadly the variant is, compared to the delta variant.

“What we can anticipate, what we’re quite confident about, is that this variant is more likely to infect and reinfect people who have been vaccinated or have immunity from prior infection,” he told CNBC’s Squawk Box Europe on Tuesday.

Read more: Pfizer submits data to FDA for authorization of Covid vaccine booster shot for general population

“But in terms of intrinsic transmissibility, irrespective of the immune system, and its virulence we know, I would say, almost nothing at this stage… We Just have to wait before we can say.”

There is quiet optimism that omicron could be a more infectious, but less virulent, version of the virus, meaning it could turn into an infection more akin to the common cold.

Deakin University epidemiologist Catherine Bennett told the Sydney Morning Herald on Monday that “there is a possibility that we are seeing a more infectious and less virulent version of the virus, which would be one of those steps along a happier route to living with the virus,” she said. “We’ve got as many signals that it might [be] OK as we’ve got signals that it might be a bit of a worry.”

Many countries are not taking any chances and have announced a ramping-up of Covid vaccinations, booster shots and more restrictive measures.

On Monday, U.S. President Joe Biden ruled out another lockdown and travel curbs for now, although it and a raft of countries have temporarily suspended travel from a number of southern African countries.

— CNBC’s Spencer Kimball contributed reporting to this story.