Normal for the FDA to wait until the U.S. clinical trial is complete. In general, evidence from other countries for efficacy can only be supportive, not the core evidence. Statistics from other countries to demonstrate safety is required. The idea is to combine data for as many subjects as possible when looking for the incidence of adverse reactions.
I didn't work on vaccine trials, but did work on submissions to the FDA for drugs that had been used in Europe for decades before a submission to the FDA for as a treatment for a new use.