WASHINGTON (AP) — President Donald Trump has announced the emergency authorization of convalescent plasma for COVID-19 patients.

While Trump is calling the move “a breakthrough,” one of his top health officials says it is “promising” and other health experts say the therapeutic needs more study before it can be celebrated.

The blood plasma is taken from patients who have recovered from the coronavirus and is rich in antibodies.

It may provide benefits to those battling with the disease, but the evidence has been inconclusive as to how it works or how best to administer it.