TORONTO -- A year into the pandemic and sick of being cooped up in their homes, many Canadians may feel like theyâre near the breaking point. But for infants and toddlers, the lack of contact with people outside of their immediate family means theyâre missing out on social and biological interactions that are key for their development, say experts. Marie-Claire Arrieta, an assistant professor in the department of physiology and pharmacology at the University of Calgaryâs Cumming School of Medicine, says that the early years up until pre-school age are critical for exposure to microorganisms that help digest our food, protect us from disease and regulate our immune system.