Pfizer plans to ask U.S. regulators to grant emergency use authorization for a second booster of its COVID-19 vaccine, CEO Albert Bourla said March 11. “Clearly there is a need in an environment of Omicron to boost the immune response,” Bourla said on CNBC’s “Squawk Box.” Pfizer’s vaccine waned over time in protection against both infection and hospitalization when the Delta variant of the virus that causes COVID-19 was dominant in the United States, real-world data and studies showed. The issue has grown more pronounced since Omicron displaced Delta in late 2021. Bourla said data Pfizer executives have seen indicates the vaccine protection “is very good” after three doses when it comes to protecting against severe disease. But that protection “doesn’t last long,” he added, with waning starting after several months. “Waning immune responses is [sic] higher for people if they have high age, they are older, or they have …