Leukemias and lymphomas account for more than half of new cancer cases in children each year. As a result of advancements in clinical protocols, survival rates for hematological malignancies in children now approximately 80% to 90%. The short-term effects of chemotherapy are well documented; however, many late effects remain unclear, notably those on the humoral immune system. The recent resistance toward childhood vaccination in some communities in conjunction with a growing number of potentially underprotected survivors could place this population at increased risk for common communicable diseases. Additionally, survivors could serve as a significant reservoir for further spread of disease within the general population. The state of the scientific knowledge regarding humoral immunity in this population is insufficient for concrete conclusions. An intensive search of the literature on various platforms was performed to identify articles reporting on the rates of protection to common vaccine-preventable diseases in survivors of pediatric hematological malignancies. Articles were selected with respect to inclusion and exclusion criteria. Quality was evaluated against specific methodological standards. Each study shows evidence that participants were lacking immunity to at least one vaccination following treatment. A majority of participants recovered immunity after revaccination, with a small percentage remaining unprotected. There is no consistency between studies regarding the rates at which immunity is present; furthermore, there are no particulars on how long immunity persists following revaccination. Vaccination represents an instrumental public health initiative for reducing morbidity and mortality globally. The clinical ramifications of losing protection against vaccine preventable diseases are therefore serious.

H7N3 and H7N7 are highly pathogenic avian influenza (HPAI) viruses and have posed a great threat not only for the poultry industry but for the human health as well. H7N9, a low pathogenic avian influenza (LPAI) virus, is also highly pathogenic to humans, and there is a great concern that these H7 subtypes would acquire the ability to spread efficiently between humans, thereby becoming a pandemic threat. A vaccine candidate covering all the three subtypes must, therefore, be an integral part of any pandemic preparedness plan. To address this need, we constructed a consensus hemagglutinin (HA) sequence of H7N3, H7N7, and H7N9 based on the data available in the NCBI in early 2012-2015. This artificial sequence was then optimized for protein expression before being transformed into an attenuated auxotrophic mutant of Salmonella Typhimurium, JOL1863 strain. Immunizing chickens with JOL1863, delivered intramuscularly, nasally or orally, elicited efficient humoral and cell mediated immune responses, independently of the route of vaccination. Our results also showed that JOL1863 deliver efficient maturation signals to chicken monocyte derived dendritic cells (MoDCs) which were characterized by upregulation of costimulatory molecules and higher cytokine induction. Moreover, immunization with JOL1863 in chickens conferred a significant protection against the heterologous LPAI H7N1 virus challenge as indicated by reduced viral sheddings in the cloacal swabs. We conclude that this vaccine, based on a consensus HA, could induce broader spectrum of protection against divergent H7 influenza viruses and thus warrants further study.