Author reply: Improving the validity of studies on the relationship between social health and immunity of older adults. - van der Velpen, Isabelle F.; Yaqub, Amber; Vernooij, Meike W.; Perry, Marieke; Vernooij-Dassen, Myrra J.F.; Ghanbari, Mohsen; Arfan Ikram, M.; Melis, René J.F. (Brain, Behavior & Immunity, 2024)