Assuming families have the option to provide child care for babies either at home (1-on-1) or at the nursery (in groups of 10-15 babies), which option is a better strategy from the point of view of the child's immune health in later life? Assume for the purposes of this question that the baby is vaccinated according to current Western immunisation programmes.
Conventional parenting wisdom holds it that sending a child to the nursery from the earliest acceptable age, e.g. 1 year, just means parents will have them home sick more times, until they reach kindergarten age, relative to the scenario of providing one-on-one daycare and enrolling them in kindergarten only later, e.g. at 3 years.
In other words, are the infections caught between roughly 1-3 years of age "a necessary evil" that is best lived sooner rather than later, in the sense of hastening the development of various antibodies and of the immune system in general? Or are such infections best avoided if 1:1 childcare is available, since the child's immunity will have plenty of opportunity to develop in later schooling (and it isn't too late for those to develop at that time)?
Research that either confirms or refutes this intuition is hard to find.