Pfizer have announced that their Chief Scientific Officer, a key figure behind the development of its COVID-19 jab, is stepping down after more than 15-years with the big pharma giant.

Mikael Dolsten served as the head of Pfizer’s research and development after he joined the company through its $68 billion acquisition of Wyeth in 2009. He became Pfizer’s chief scientist in 2010.

Reuters reports: During his tenure, Comirnaty — jointly developed by Pfizer and BioNTech — became the first COVID vaccine to get an approval from the U.S. Food and Drug Administration in 2021, just 13 months after its trial began, in a record time to approval for any shot or therapeutic.

Pfizer also developed and launched multi-billion dollar products such as heart disease drug Vyndaqel and blood thinner Eliquis, after the company struggled to remain competitive with other drugmakers.

“After more than 15 years as the architect of Pfizer’s exceptional scientific and research and development resurgence, Mikael and I recently discussed starting the process to look for his successor,” said CEO Albert Bourla.

The company said its process to identify a successor is expected to last several months.

A new chief scientist would come at a time when billions of dollars in COVID vaccine and treatment sales have disappeared as pandemic worries ease.