How the immune response to vaccines is created, maintained and measured: addressing patient questions about vaccination

The effect of stress on the antibody response after vaccination in children aged 0-18 years: A systematic review

Stress has been associated with less effective vaccine responses in adults. This review aims to investigate the evidence for a similar association in children. A systematic review search was conducted in January 2021 in three databases: Medline, Embase and PsycInfo. An updated search of the Medline database was systematically conducted until the most recent update on September 25th, 2023, to ensure the inclusion of the most current research available. Keywords related to stress, vaccines and children were used, and a total of 7263 (+1528) studies were screened by two independent investigators. Six studies met the inclusion criteria for data extraction and analysis. For quality assessment of the studies, the risk of bias in non-randomized studies-of interventions (ROBINS-I) tool was applied. Most of the studies suggest a negative role of stress on vaccine responses. However, the scarcity of studies, lack of confirmatory studies, risk of bias and heterogeneity according to age, type of vaccine, measures of stress and vaccine responses prevent a clear conclusion. Future studies should emphasize the use of as strict study designs as possible, including well-defined stress metrics and thorough examination of both pre- and post-vaccination responses. Systematic review registration: Prospero CRD42021230490.

Kinetic characteristics of euflammation: the induction of controlled inflammation without overt sickness behavior

We found recently that controlled progressive challenge with subthreshold levels of E. coli can confer progressively stronger resistance to future reinfection-induced sickness behavior to the host. We have termed this type of inflammation "euflammation". In this study, we further characterized the kinetic changes in the behavior, immunological, and neuroendocrine aspects of euflammation. Results show euflammatory animals only display transient and subtle sickness behaviors of anorexia, adipsia, and anhedonia upon a later infectious challenge which would have caused much more severe and longer lasting sickness behavior if given without prior euflammatory challenges. Similarly, infectious challenge-induced corticosterone secretion was greatly ameliorated in euflammatory animals. At the site of E.coli priming injections, which we termed euflammation induction locus (EIL), innate immune cells displayed a partial endotoxin tolerant phenotype with reduced expression of innate activation markers and muted inflammatory cytokine expression upon ex vivo LPS stimulation, whereas innate immune cells outside EIL displayed largely opposite characteristics. Bacterial clearance function, however, was enhanced both inside and outside EIL. Finally, sickness induction by an infectious challenge placed outside the EIL was also abrogated. These results suggest euflammation could be used as an efficient method to "train" the innate immune system to resist the consequences of future infectious/inflammatory challenges.