Pfizer could have data on how well its Covid-19 vaccine works in kids under age 5 by the end of the year, according to CEO Albert Bourla. "We have a study in children 6 months to 2 years and then another cohort of children 2 to 5 years," Bourla told NBC News chief White House correspondent Kristen Welker. "So [by] end of the year, beginning of next year, when we see the data, we will know more."