(Reuters) -Pfizer Inc and partner BioNTech have completed the filing with the U.S. drugs regulator seeking authorization for their COVID-19 vaccine in children under 5 years of age. The filing with the U.S. Food and Drug Administration (FDA), completed on Wednesday, included data showing three lower-dose shots of the vaccine generated a strong immune response in children as young as 6 months of age. No COVID-19 shot is yet approved for children in that age group in most parts of the world. It remains unclear how many parents will get their young ones vaccinated as demand has been low in kids a…