Based on the FDA document, the vaccine did not work after the originally planned two doses. They had to go back and expand the study to 3 doses with a gap of at least 8 weeks after the 2nd dose. The third dose they have separated into "all-available efficacy" and " Evaluable efficacy" populations. 1206 children in the all available group (which i believe includes the evaulable group) from children of 6-23 months did not receive the third dose which is about 70%.

Their definitions of the groups make it confusing as hell but I think thats intentional because 1) its not safe 2) it doesn't work and 3) theres no emergency.

Edit: There is more info than I can type out here. If you're curious I was looking at pages 17 - 22 of https://www.fda.gov/media/159195/download