The Food and Drug Administration’s emergency authorization for blood plasma as a COVID-19 treatment has been put on hold after top federal health officials warned that evidence for the effectiveness of the treatment was too weak, the New York Times reports. President Trump previously backed the use of plasma, lauding it as a “beautiful ingredient” that can be pumped into the veins of COVID-19 sufferers with the intention of providing them with disease-fighting antibodies. However, clinical trials have yet to prove that plasma helps people suffering from the novel coronavirus, and top health officials—including Dr. Anthony Fauci—have urged their colleagues to wait for more evidence before approval. Emergency authorizations don’t require the same level of evidence as a full FDA approval. One was issued for the malaria drug hydroxychloroquine—but it was rescinded months later after the drug was found to be ineffective against the virus. The FDA hasn’t officially confirmed the Times report.