The first round of a coronavirus vaccine trial in San Antonio is underway. Participants in the double-blind Pfizer trial got their first doses on Thursday. To take part in the trial, you must be at least 18-years old. Call Clinical Trials of Texas, the San Antonio lab hosting the study, to be screened. Researchers assure participants they can't catch the coronavirus from the Pfizer vaccine. If the vaccine proves effective, it could be available for public use as soon as the start of next year. A different vaccine trial by Moderna is set to begin today.