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* Travel stocks edge higher after Pfizer vaccine update
* Big Tech mixed after rally from earlier in the week
* Indexes: Dow off 0.20%, S&P flat, Nasdaq up 0.30% (Adds comments, updates prices to early afternoon)
By Devik Jain and Shreyashi Sanyal
Dec 8 (Reuters) - U.S. stock indexes struggled for direction on Wednesday after a strong start to the week, as investors digested a fresh update on Pfizer and BioNTech's COVID-19 vaccine, while the fast-spreading Omicron variant kept bigger bets in check.
Pfizer and BioNTech said their three-shot course of COVID-19 vaccine was able to neutralize the new Omicron variant in a laboratory test and they could deliver an upgraded vaccine in March 2022 if needed.
"We've had a really strong start to the week. So there is sort of a pause in that rally," said Fiona Cincotta, senior financial markets analyst at City Index.
"While we've got one good news from Pfizer, it does require three jabs ... so it does sort of feel that there's a bit of a race on now as to how quickly booster jabs can get rolled out and will countries be able to avoid lockdowns."
Travel stocks rebounded, with the S&P 1500 Airlines index up 3.7%, while Norwegian Cruise Line led gains among cruiseliners.
Even as the vaccine update helped calm nerves earlier in the session, there is still very little known about the new variant of the coronavirus. Markets were cautious after reports earlier in the day said Britain could implement tougher COVID-19 measures, including advice to work from home, as early as Thursday in a bid to slow the spread of the Omicron variant.
Six of the 11 major S&P 500 sector indexes rose. Financials and utilities led declines.
Technology-oriented growth stocks, which have been on the rise since the beginning of the week, were mixed.
Tesla Inc, Alphabet, Microsoft, Amazon and Nvidia Corp shed between 0.3% and 1.4%, while Apple and Meta Platforms moved higher.
Wall Street swung wildly last week as investors fretted that the spread of the new variant could force countries to lay down new restrictions, upending a global recovery at a time when central banks around the world are contemplating a move to pre-pandemic monetary policy environment.
WHO director-general Tedros Adhanom Ghebreyesus said governments should urgently reassess their national responses to COVID-19 and accelerate their vaccination programs to slow the spread of the Omicron variant.
At 11:50 a.m. ET, the Dow Jones Industrial Average was down 72.73 points, or 0.20%, at 35,646.70, the S&P 500 was down 0.34 points, or 0.01%, at 4,686.41, and the Nasdaq Composite was up 47.14 points, or 0.30%, at 15,734.06.
Goodyear Tire & Rubber Co rose 5.8% after Deutsche Bank upgraded the stock to "buy" from "hold".
Stanley Black & Decker added 4.3% after Sweden's Securitas agreed to buy its electronic security solutions business for $3.2 billion.
Advancing issues outnumbered decliners by a 1.67-to-1 ratio on the NYSE and a 2.00-to-1 ratio on the Nasdaq.
The S&P index recorded 27 new 52-week highs and no new low, while the Nasdaq recorded 27 new highs and 28 new lows. (Reporting by Devik Jain and Shreyashi Sanyal in Bengaluru; Editing by Maju Samuel)