A B777 departed the gate after receiving additional life vests and then flew to its destination without the proper infant life jackets because of a misunderstanding about the proper vests types required.

Narrative

During preflight safety check there were 18 infant life vests 2 less than the 20 required. I notified the Purser who called for them. A Maintenance Person brought two child/adult vests. I told him I needed infant vests. He said that on this reconfigured aircraft the vests were not different. I asked 'are you sure?' He said yes and told me he would bring the right ones. He took all infant life vests off the plane. Boarding continued and I got busy. Immediately after the door closed I realized that the vests had not been brought. I told the Purser who communicated with the pilots. The airplane door was opened and the Maintenance man was at the door with the two bags filled with life vest. She handed them to us and the door was closed immediately. Instructed by the Purser; two of us handed out the vest to children as the flight was taxiing. As the flight continued I began to think that it did not seem right that the vests we were given for children were the same as the adults. After the meal service I spoke of my doubts to the Purser looked in the handbook. We saw that 'all aircraft must have infant life vests or dual chamber adult vests for PAX under 35 lbs.' We had no such life vests for infants on our flight.