These are the headline-grabbing companies in premarket trading.

Regeneron Pharmaceuticals (REGN) — Regeneron shares fell more than 1% in the premarket after the company said its Covid-19 antibody cocktail and similar drugs could be less effective against the omicron Covid variant.According to the drugmaker, mutations found in this variant could indicate “reduced neutralization activity for both vaccine-induced immunity and monoclonal antibodies conveyed immunity.”

Moderna (MRNA), Pfizer (PFE) — Shares of vaccine makers were on watch after Moderna CEO Stephane Bancel told the Financial Times he expects existing vaccines to be less effective against the omicron variant. Oxford University stated that there was no evidence yetThe current vaccines are not effective in protecting against severe diseases like omicron. Scientists are currently studying new variants and their ability to overcome prior immunity. Moderna shares plunged more than 2% during early morning trading. BioNTech shares declined more than 5 percent. Pfizer shares rose by about 1%. Novavax shares increased by more than 2 percent

Dollar Tree (DLTR) — Shares of Dollar Tree fell more than 2% in premarket trading after Goldman downgraded the stockA buy is a sell. According to the firm, the stock was too costly at present levels because Dollar Tree’s return story has been priced in.

SolarEdge Technologies (SEDG) — Shares of SolarEdge pulled back about 3% premarket after Morgan Stanley downgraded the stockFrom overweight to equivalent-weight Morgan Stanley indicated that the stock seems to have been fully valued due to a recent trend.

Meta Platforms (FB) — Shares of Facebook-parent Meta were slightly lower in the premarket after a U.K. regulator told the company it must sell GIF-sharing platform Giphy. The Competition and Markets Authority said Meta’s acquisition of Giphy would reduce competition between social media platforms.

Beyond Meat (BYND), Oatly (OTLY) — Shares of meat alternative producer Beyond Meat and plant-based dairy company Oatly each retreated more than 1% in early morning trading after HSBC initiated coverage of the stocks at a “reduce” rating. HSBC reported that the potential for increased competition means that the expected growth will not be sufficient to allow many of the participants to realize their high-growth ambitions in a market report.

Twitter (TWTR), Square (SQ) — Shares of Twitter and Square moved higher in the premarket the day after Jack Dorsey announced he is stepping down as CEO of Twitter. Dorsey had been serving as chief executive for both Square’s digital payments platform and social media platform. Bank of America upgradedSquare will neutralize from underperform, and reiterate its buy rating for Twitter.