FRANKFURT/BERLIN, Nov 30 (Reuters) - The World Health Organization warned countries on Tuesday not to impose blanket travel bans over the new Omicron coronavirus variant as governments and scientists tried to figure how much protection current vaccines would offer against the strain. Financial markets fell sharply after the head of drugmaker Moderna said existing COVID-19 vaccines would be less effective against the Omicron variant, but they recovered strongly after more reassuring comments from European officials. BioNTech"s chief executive also struck a cautiously positive note, saying BioNTech and Pfizer"s (PFE.N) vaccine was likely to offer strong protection against severe disease from Omicron. The WHO said that blanket travel bans would not stop the new variants spread but would place a "heavy burden" on lives and livelihoods. It advised governments to take measures such as screening or quarantine of international passengers if the evidence warranted it. However, people who are unwell or at higher risk of developing severe COVID-19, including those 60 years or older, should postpone travel, the WHO said in a statement. WHO Secretary General Tedros Adhanom Ghebreyesus said he understood the concerns about Omicron. But he added: "I am equally concerned that several member states are introducing blunt, blanket measures that are not evidence-based or effective on their own, and which will only worsen inequities." European Medicines Agency (EMA) executive director Emer Cooke told the European Parliament that existing vaccines will continue to provide protection. read more Andrea Ammon, chair of the European Centre for Disease Prevention and Control (ECDC), said the cases of Omicron so far confirmed in 10 European Union countries were mild or without symptoms, although in younger age groups. read more News of Omicron"s emergence wiped roughly $2 trillion off global stocks on Friday, after it was identified in southern Africa and announced on Nov. 25. The Pan-European STOXX 600 index, spooked by fears that vaccine resistance might trigger restrictions that would choke off a nascent recovery, was down 0.5% at around 1644 GMT on Tuesday, having fallen as much as 1.5% in early trade. In New York at 1605 GMT, the Dow Jones Industrial Average (.DJI) and the S&P 500 (.SPX) respectively were down about 1.3% and 1.26%. "There is no world, I think, where (the effectiveness) is the same level...we had with Delta," Moderna CEO Stephane Bancel told the Financial Times. "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"." read more Reuters could not reach Moderna for comment. The University of Oxford said there was no evidence that current vaccines would not prevent severe disease from Omicron, but that it was ready to rapidly update its shot, developed with AstraZeneca (AZN.L), if necessary. read more "The World Health Organization classified Omicron as a "variant of concern," due to the number of mutations that might help it spread or evade antibodies from prior infection or vaccination. "The World Health Organization classified Omicron as a "variant of concern," due to the number of mutations that might help it spread or evade antibodies from prior infection or vaccination. LAB TESTS Regeneron Pharmaceuticals said its COVID-19 antibody cocktail and other similar antiviral treatments could be less effective against the latest variant. read more Travellers and flight crew members arrive at the international terminal at Sydney Airport, as countries react to the new coronavirus Omicron variant amid the coronavirus disease (COVID-19) pandemic, in Sydney, Australia, November 30, 2021. REUTERS/Loren Elliott People wearing face masks to prevent the spread of the coronavirus disease (COVID-19), ride in a bus in Hong Kong, China November 29, 2021. REUTERS/Lam Yik A man puts on a face mask to prevent the spread of the coronavirus disease (COVID-19), while working at a community nucleic acid testing center in Hong Kong, China November 29, 2021. REUTERS/Lam Yik 1/5 People wearing face masks to prevent the spread of the coronavirus disease (COVID-19), ride in a bus in Hong Kong, China November 29, 2021. REUTERS/Lam Yik EMA"s Cooke said lab tests for "cross neutralisation" would take about two weeks. If there were a need to change COVID-19 vaccines, new ones could be approved within three or four months, she said. "Vaccination will likely still keep you out of the hospital," said John Wherry, director of the Penn Institute for Immunology in Philadelphia. Moderna and fellow drugmakers BioNTech and Johnson & Johnson (JNJ.N) are already working on vaccines that specifically target Omicron. Moderna has also been testing a higher dose of its existing booster. read more BioNTech Chief Executive Ugur Sahin told Reuters that BioNTech and Pfizer"s (PFE.N) vaccine was likely to offer strong protection against severe disease from the new variant. Sahin said he expects lab tests to show some loss of protection against mild and moderate disease due to Omicron but the extent of that loss was hard to predict. BORDER CONTROLS But border closures have already cast a shadow over economic recovery with parts of Europe now seeing a fourth wave of infections as winter sets in. read more Many of the new travel restrictions have focused, to South Africa"s fury, on banning flights to and from southern Africa. Japan confirmed its first case of the new variant on Tuesday, in a traveller from Namibia. Australia found that a person with Omicron had visited a busy shopping centre in Sydney while probably infectious. An upsurge in new coronavirus variants and poor access to vaccines in developing countries threaten a full recovery from the COVID-19 pandemic. An upsurge in new coronavirus variants and poor access to vaccines in developing countries threaten a full recovery from the COVID-19 pandemic. Britain and the United States have both pushed their booster programmes in response to the new variant. London said international arrivals would have to self-isolate until they get a negative result in a PCR test. Greece said vaccination would be compulsory for the over-60s, the group seen as most vulnerable to COVID-19. Australia on Monday delayed the reopening of its international borders by two weeks, less than 36 hours before foreign students and skilled migrants were to be allowed back. But in Germany, a current hotspot of the previous significant variant, Delta, the seven-day average infection rate fell slightly for the first time in three weeks after new restrictions to slow transmission. read more Sources said chancellor-in-waiting Olaf Scholz supported making vaccination against COVID-19 compulsory and backed barring the unvaccinated from non-essential stores. Neighbouring Austria, which imposed its fourth full lockdown last week after a surge in infections, also registered a drop. But France registered its highest daily infection tally since April. And the Dutch health authority said Omicron was already spreading in the Netherlands, where intensive care beds are running out and measures including restrictions on hospitality have yet to take effect. read more The curbs on travellers from southern Africa have highlighted the inequality of vaccine distribution, which may have given the virus more opportunities to mutate. The passenger liner Europa was docking in Cape Town on Tuesday in what was meant to be the official start of the first cruise ship season in South Africa"s top tourist hub since the pandemic. After Omicron was discovered while they were at sea, many passengers were expected to fly straight home. read more