I don't know the specifics in this situation but I work at a university where vaccines are actively developed (for many things). Unless there's a significant financial push, administration to children lags far behind to ensure that random autoimmune complications with vaccine are far below the risks of catching the virus and having a serious reaction.

Also, you can pretty much anticipate pregnant women will be the last two be approved for anything. Pregnancy complications are common enough that no one wants to mess with that whole situation until you're certain you won't have cross antigen reactivity in the host