Fourth..

Pfizer CEO Albert Bourla said a vaccine that targets the omicron variant of Covid will be ready in March, and the company's already begun manufacturing the doses.

Real-world data from the United Kingdom has shown that Pfizer and Moderna's vaccines are only about 10% effective at preventing symptomatic infection from omicron 20 weeks after the second dose, according to study from the U.K. Health Security Agency. 

However, the original two doses still provide good protection against severe illness, the study found. Booster shots are up to 75% effective at preventing symptomatic infection, according to the study. (For how long though?)

Bourla said it's not clear whether a fourth dose is needed. He said Pfizer will conduct experiments to make to determine if another dose is necessary.