WASHINGTON, Dec 23 (Reuters) - Available data indicates that both Merck"s (MRK.N) and Pfizer"s (PFE.N) COVID-19 anti-viral treatments are effective against the Omicron variant of the coronavirus, a top U.S. Federal Drug Administration official said on Thursday. "The available data that we have indicates that both paxlovid and molnupiravir are effective against Omicron.," said Dr. Patrizia Cavazzoni, adding that both drugs interfere with how the virus replicates, a process that isn"t altered across variants. The availability of other treatments should be the first consideration for doctors wishing to prescribe Merck"s molnupiravir, said Cavazzoni, director the FDA"s Center for Drug Evaluation and Research. (This story was refiled to fix a typo in paragraph 3 from "describe" to "prescribe".)