Poor vaccine responders mask the true trend in vaccine effectiveness against progression to severe disease.

Vaccines can reduce an individual's risk of infection and their risk of progression to severe disease given infection. The latter effect is less commonly estimated but is relevant for vaccine impact modeling and cost-effectiveness calculations. Using a motivating example from the COVID-19 literature, we note how vaccine effectiveness against progression to severe disease can appear to increase from below 0 % to over 70 % within 8 months.

A comparative immunological assessment of multiple clinical-stage adjuvants for the R21 malaria vaccine in nonhuman primates.

Authorization of the Matrix-M (MM)-adjuvanted R21 vaccine by three countries and its subsequent endorsement by the World Health Organization for malaria prevention in children are a milestone in the fight against malaria. Yet, our understanding of the innate and adaptive immune responses elicited by this vaccine remains limited. Here, we compared three clinically relevant adjuvants [3M-052 + aluminum hydroxide (Alum) (3M), a TLR7/8 agonist formulated in Alum; GLA-LSQ, a TLR4 agonist formulated in liposomes with QS-21; and MM, the now-approved adjuvant for R21] for their capacity to induce durable immune responses to R21 in macaques.

Preservation of naive-phenotype CD4+ T cells after vaccination contributes to durable immunity.

Memory T cells are conventionally associated with durable recall responses. In our longitudinal analyses of CD4+ T cell responses to the yellow fever virus (YFV) vaccine by peptide-MHC tetramers, we unexpectedly found CD45RO-CCR7+ virus-specific CD4+ T cells that expanded shortly after vaccination and persisted months to years after immunization. Further phenotypic analyses revealed the presence of stem cell-like memory T cells within this subset.

Differentiation marker-negative CD4 T cells persist after yellow fever virus vaccination and contribute to durable memory.

Factors that contribute to durable immunological memory remain incompletely understood. In our longitudinal analyses of CD4 T cell responses to the yellow fever virus (YFV) vaccine by peptide-MHC tetramers, we unexpectedly found naïve phenotype virus-specific CD4 T cells that persisted months to years after immunization. These Marker negative T cells (T) lacked CD95, CXCR3, CD11a, and CD49d surface protein expression, distinguishing them from previously discovered stem-cell memory T cells.

Infants and young children generate more durable antibody responses to SARS-CoV-2 infection than adults.

As SARS-CoV-2 becomes endemic, it is critical to understand immunity following early-life infection. We evaluated humoral responses to SARS-CoV-2 in 23 infants/young children. Antibody responses to SARS-CoV-2 spike antigens peaked approximately 30 days after infection and were maintained up to 500 days with little apparent decay.