CureVac NV (NASDAQ:CVAC) stock soared 29.5% on Thursday pre-market trading after German biotech firm BioNTech SE (NASDAQ:BNTX) said it would acquire the company for approximately $1.25 billion.

In a note Thursday, Wells Fargo analysts flagged a narrow rally breadth as a potential risk for the S&P 500, despite the index’s recent rebound.