A panel of U.S. health advisers on Tuesday narrowly backed a closely watched COVID-19 pill from Merck, setting the stage for a likely authorization of the first drug that Americans could take at home to treat the coronavirus. A Food and Drug Administration panel voted 13-10 that the drug’s benefits outweigh its risks, including potential birth defects if used during pregnancy. The recommendation came after hours of debate about the drug’s modest benefits and potential safety issues. Experts backing the treatment stressed that it should not be used by anyone who is pregnant and called on the FDA to recommend extra precautions before the drug is prescribed, including pregnancy tests for women of child-bearing age. The vote specifically backed the drug for adults with mild-to-moderate COVID-19 who face the greatest risks, including older people and those with conditions like obesity and asthma. Most experts also said the drug shouldn’t be …