The S&P 500 (SPX) managed on Monday to claw back more than half of the losses from Friday after President Biden said there was no current need for further lockdowns, says Jon Markman, growth-stock specialist and editor of Strategic Advantage.

The benchmark S&P 500 soared to 4,655, a gain of 1.3%. The big rally retakes a key pivot level at 4,650, putting bulls back in control of the trend. It will be important for bulls to build on gains Tuesday, though.

One concern is the rally Monday was concentrated in big tech winners. Cyclicals like banks and industrials surrendered early gains and finished lower.

Critical support for the benchmark is still 4,530. Expect aggressive buying into any decline to that level.

The infectiousness of the new Omicron variant and the relative severity of its symptoms won't be known for another two weeks, officials and experts said Monday. Pharmaceutical companies said current treatments are likely to prove effective, adding that vaccines could be modified as needed in months.

The Dow rose 0.7% to 35,135.94. Breadth was even today, with the advancers slightly in the lead. There were 61 new highs vs 444 new lows. That is an oversold condition.

Big caps on the new high list included Pfizer (PFE), Costco (COST), Advanced Micro Devices (AMD), NextEra Energy (NEE), and Lam Research (LRCX).

Technology heavyweights fared best alongside energy producers, utilities, and real estate investment trusts. Drugmakers, telecoms, financials, and farm machinery suppliers lagged.

The 10-year US Treasury yield rose five basis points to 1.53%, after tumbling 16 basis points Friday. West Texas Intermediate crude oil rose $1.37 to $69.52 per barrel.

The South African doctor who first drew attention to the Omicron variant of Covid-19 said the strain's symptoms appear to be "extremely mild," encouraging market optimists. If the strain proves less severe as well as more transmissible, "this is bullish not bearish for markets," tweeted billionaire investor Bill Ackman.

"If people are vaccinated and wear their masks, there's no need for lockdowns," US President Joe Biden said at a press conference Monday.

Alphabet (GOOG, GOOGL), Microsoft (MSFT), and Apple (AAPL) all gained more than 2% each, while Amazon (AMZN) added 1.6%. Computer processors supplier Nvidia (NVDA) surged 6%.

Moderna (MRNA) shares jumped nearly 12% after the Covid-19 vaccine maker's CEO said a new vaccine tailored to Omicron would take months, while an increased booster dose could address the threat "right away." The stock is up more than 50% in just over three weeks, reversing the heavy losses after the company cut its annual revenue outlook in early November.

Pfizer's (PFE) stock fell 3% after setting a record high earlier in the session, as the drugmaker's CEO said the company now expects to produce 80 million courses of treatment of its experimental oral antiviral Paxlovid by the end of 2022, up from a recent forecast of 50 million.

Twitter (TWTR) dropped 2.7% after co-founder Jack Dorsey stepped down as CEO effective immediately, succeeded by Parag Agrawal, the company's chief technical officer. Dorsey is expected to remain on the company's board at least through next year.

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