Pfizer has amended its COVID-19 vaccine trial for younger children and expects results in several months, a researcher said Wednesday. The study has been adjusted from two doses to three doses in light of the growing body of evidence showing the primary regimen’s effects wane as time goes on from vaccination, Dr. Alejandra Gurtman, part of Pfizer’s clinical research and development group, told a panel that advises the Centers for Disease Control and Prevention (CDC) on vaccine policy during a virtual meeting. Pfizer announced last month that a lower dosage of its vaccine did not provoke an adequate immune response among children aged 2 to 5. The company relies on immunobridging, or comparable immune responses to already-cleared groups, to convince regulators to clear its shot for younger age groups. Instead of increasing the dosage amount, Pfizer and German partner BioNTech decided to add a third dose to the study. “It is …