CSL's (ASX:CSL) flu revenue impact for the current Northern Hemisphere season is far worse than anticipated, driving the downgrade in the firm's revenue growth guidance, according to a Tuesday note by Jarden.

CSL cut its fiscal year 2026 revenue growth guidance to a range of 2% to 3% from its previous forecast of about 4% to 5%. The company also narrowed its net profit after tax and authorization growth outlook to a range of about 4% to 7% from its earlier guidance of about 7% to 10%.

The firm's Seqirus flu revenue is now expected to fall by "mid-teens" compared to a previous outlook of a decline of "high single digit". The Behring business appears to be performing in line with expectations.

The investment firm recommended an overweight rating on CSL and a price target of AU$304.17 per share.