Activist investor Starboard Value has taken a stake of about $1 billion in Pfizer and wants the U.S. drug giant to make changes to turn its performance around, sources familiar with the matter said on Sunday.

Starboard Value has taken a stake in Pfizer, people familiar with the matter said.The drug giant's stock price has dropped significantly since its COVID-19 vaccine rollout.Starboard's stake in Pfizer is reportedly worth about $1 billion.

Starboard has reached out to former Pfizer CEO Ian Read and ex-finance chief Frank D'Amelio, and both have expressed interest in supporting the activist investor's turnaround efforts, reports said.