Have any studies been completed yet on immune system efficiency/suppression after covid restrictions (masks, hand sanitizer etc) ? In Australia we were very l

Have any studies been completed yet on immune system efficiency/suppression after covid restrictions (masks, hand sanitizer etc) ? In Australia we were very lucky with the COVID situation. And purely annecdotal, but I know many people who haven't been sick at all during the pandemic. But as we approach winter here and perhaps no longer hand sanitize appropriately, many of these people are becoming "the most unwell [they] have been in years".