Ключевые слова: background, bacteria, bacterium, blackboard, blue, chalkboard, closeup, concept, danger, defense, epidemic, flu, health, heart, hygiene, immune, immunity, immunodeficient, immunology, immunotherapy, infection, infectious, medical, medicine, ncov, nobody, object, pandemic, prevent, prevention, protection, safety, shaped, support, system, table, top, vaccination, view, virus, wooden, word,