Carlo Allegri/Reuters Pfizer CEO Albert Bourla on Friday said there will be more data on children under five receiving a COVID-19 vaccine by the end of the year. Pfizer has begun pediatric vaccine trials. Moderna and Johnson & Johnson are also planning to conduct trials. Pfizer's announcement comes as the new Omicron variant begins to spread in the United States. Pfizer CEO Albert Bourla on Friday said the company expects to know more about the effectiveness of its vaccines in children under 5 by the end of the year. "We have a study in children six months to two years and then another cohort of children 2 to 5 years," Bourla said, speaking in an interview with NBC News.