The announcement of the return to in-person learning in the city came Thursday from Dr. Janet DeMille, the medical officer of health for the Thunder Bay District Health Unit (TBDHU), who credited an improvement in the number and rate of COVID-19 cases in the district in recent weeks. Teacher unions worry about safety But the decision to return to in-person learning came against the recommendation of the teachers' union. Seeley said he has been advocating for schools to remain virtual at least until all education staff in Thunder Bay are vaccinated, with the goal of protecting them against COVID-19 variants, which reports suggest are more virulent and more deadly.