From ALPA http://www.alpa.org/news-and-events/...lu-vs-covid-19
'And since no trial COVID-19 vaccine has full FDA approval, the FAA considers participation in COVID-19 vaccine trials medically disqualifying for pilots for an indefinite period. ALPA representatives are working with the FAA to better define a policy as the science evolves. In Canada, the director of Civil Aviation Medicine stated that participation in medical trials isn’t considered compatible with aviation medical certification.'