The benefits of routines for children have been consistently demonstrated in previous literature. However, factors that may confer risks for child routines have seldom been examined, particularly in families where parents and grandparents co-care the children. This study aimed to investigate the associations of parents' and grandparents' depressive symptoms with preschoolers' daily routines in Chinese three-generation families and to determine whether household chaos mediated or moderated the associations. The participants were from 171 urban three-generation families where mothers, fathers, and grandmothers (97 paternal and 74 maternal) were primary caregivers. Mothers, fathers, and grandmothers reported their depressive symptoms at Wave 1; at Wave 2 (during the COVID-19 pandemic), caregivers reported household chaos and child routines. The results revealed that child routines were negatively predicted by parents' joint depressive symptoms rather than grandmothers' depressive symptoms. In the associations, household chaos acted as a mediator rather than a moderator. Specifically, household chaos marginally mediated the associations between parents' and grandmothers' depressive symptoms and child routines only in maternal three-generation families. These findings suggest that in three-generation families, caregivers with more depressive symptoms may elicit more chaotic family environments, which may in turn compromise their children's daily routines.

Coxiella burnetii is a gram-negative bacterium that causes acute and chronic Q fever. Because of the severe adverse effect of whole-cell vaccination, identification of immunodominant antigens of C. burnetii has become a major focus of Q fever vaccine development. We hypothesized that secreted C. burnetii type IV secretion system (T4SS) effectors may represent a major class of CD8+ T-cell antigens, owing to their cytosolic localization. Twenty-nine peptides were identified that elicited robust CD8+ T-cell interferon γ (IFN-γ) recall responses from mice infected with C. burnetii. Interestingly, 22 of 29 epitopes were derived from 17 T4SS-related proteins, none of which were identified as immunodominant antigens by using previous antibody-guided approaches. These epitopes were expressed in an attenuated Listeria monocytogenes vaccine strain. Immunization with recombinant L. monocytogenes vaccines induced a robust CD8+ T-cell response and conferred measurable protection against C. burnetii infection in mice. These data suggested that T4SS effectors represent an important class of C. burnetii antigens that can induce CD8+ T-cell responses. We also showed that attenuated L. monocytogenes vaccine vectors are an efficient antigen-delivery platform that can be used to induce robust protective CD8+ T-cell immune responses against C. burnetii infection.