depends on what you mean by proven.
What is an emergency use authorization (EUA)?
In an emergency, like a pandemic,
it may not be possible to have all the evidence that the FDA would usually have before approving a drug, device, or a test.
When there is a declared emergency, the FDA can make a judgment that it's
worth releasing something for use even without all the evidence that would fully establish its effectiveness and safety. If there’s evidence that strongly suggests that patients have benefited from a treatment or test, the agency can issue an EUA to make it available.
What Is Emergency Use Authorization?
The FDA is making a trade-off on need for treatment vs need for full testing of safety and efficacy.
I wouldn't blame a parent for waiting a while for more evidence to come in or full FDA approval before proceeding.