Differences in the immune response to SARS-CoV-2 between adults and children may explain why kids tend to get milder forms of COVID-19. Researchers found that infected children had lower T cell responses to the virus compared with infected adults, and lower levels of antibodies to other coronaviruses such as the virus responsible for the common cold. They suggest that a lack of prior immunity to coronaviruses and reduced T cell activation could lead to milder COVID-19 in children, but it is not yet clear why that might be the case. Precautions still needed to prevent resistant strains With around 56 per cent of Canada’s total population fully vaccinated, we are in the danger zone for the emergence of resistant strains of the virus if other precautions are relaxed, according to a new computer model. The model suggests that a fast rate of vaccination decreases the probability that a resistant strain may emerge. But if precautions like mask-wearing, physical distancing and aggressive testing and tracing are relaxed after most people have been vaccinated, the probability of a resistant strain arising greatly increases — and resistant strains are most likely to emerge around the time when 60 per cent of the population has been vaccinated.