European stock markets have fallen after Moderna boss announces doubts over vaccine effectiveness against the new Omicron variant.
Stephane Bancel told the Financial Times that he thought there would be a "material drop" in vaccine effectiveness.
The new Covid variant was first discovered in South Africa on November 9.
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It has resulted in new restrictions in the UK to help battle its spread including the return of mandatory face coverings and PCR test requirements for people entering the country.
Mr Bancel has predicted that current vaccines will be less effective against the Omicron variant and that it could be months until drugs companies can produce an updated vaccine.
"There is no world, I think, where [the effectiveness] is the same level," he said.
"I think it's going to be a material drop. I just don't know how much because we need to wait for the data.
"But all the scientists I've talked to are like, 'this is not going to be good'."
Despite Mr Bancel's warning, others in the sector have announced more positive results regarding the vaccine's effectiveness on the new variant.
European Medicines Agency (EMA) executive director Emer Cooke told the European Parliament that even if the new variant becomes more widespread, existing vaccines should continue to provide some level of protection.
Furthermore, the World Health Organization has said it could take weeks to determine how severe Omicron infections could be, and how much protection current vaccines give.
The University of Oxford also added that there was no evidence that current vaccines would not prevent severe disease from Omicron - it also stated it was ready to rapidly develop an updated version of the AstraZeneca vaccine if necessary.
Joe Capurso, a currency strategist for Commonwealth Bank of Australia, said: "It's not good news, and it's coming from someone who should know.
"Markets have reacted in exactly the way you'd expect them to."
It comes as the UK's FTSE 100, Germany's Dax, and France's Cac 40 have fallen more than 1.5 per cent each, and the pan-European Stoxx 600 dropped 1.5 per cent - its lowest levels in nearly seven weeks.
Tokyo's Nikkei index fell down 1.6 per cent while crude oil prices fell nearly 3 per cent.
Alongside this, the Australian dollar has hit a one-year low.
Solid assets, usually considered to be safer in times of uncertainty, were being scrambled for including gold, German government bonds, and the yen.
Since the new Omicron variant was discovered, the FTSE 100 index suffered its biggest dip in over a year.
While stock markets have increased since last Friday (November 26) they are still way below previous levels.
Despite this, stock markets more focused on UK firms such as the FTSE 100 and the FTSE 250 are significantly higher than this time last year.
How do stock prices affect me?
Changes in the stock market can have direct impacts on your personal finances.
Most notably, the millions of people in the UK with a pension which is invested by pension schemes.
The savings in these pensions schemes are influenced by the performance of investments, both positive and negative.
When someone reaches retirement age, they may use their pension pot to buy a retirement income or annuity - the more positive the investment, the more income that retiree will receive.
