Strong versus weak is an unhelpful yardstick to assess whether or not immune function is sufficient. After all, aren’t allergies and autoimmunities signs of strong immune responses? Clearly, immune responses being strong don’t preclude them from also being counter-productive.
In addition, often what differentiates individuals who successfully fight off infections from those who develop its chronic consequences is the nature rather than the strength of their immune responses, i.e., what rather than how much. A classic example is tuberculosis (TB). The vast majority of TB infected people never go on to develop disease. The relatively minor proportion who do are largely characterized by strong antibody responses that are nevertheless ineffective in getting rid of it, i.e., immune responses that vary not in strength but in type/class from the ones in those who successfully fight off TB.
Such examples highlight that rather than strength, ability to efficiently fight off infections comes from launching and sustaining the classes of immune responses that can appropriately deal with a threat while causing least harm to the body itself. Thus, rather than strength, immune response class better predicts capacity to efficiently fight off infections. When the right immune response classes are deployed against a threat, they appear to also carry the capacity for requisite strength to see the threat off with minimal collateral damage.