Host Factors Impact Vaccine Efficacy: Implications for Seasonal and Universal Influenza Vaccine Programs

Abstract

Influenza is a global public health problem. Current seasonal influenza vaccines have highly variable efficacy, and thus attempts to develop broadly protective universal influenza vaccines with durable protection are under way. While much attention is given to the virus-related factors contributing to inconsistent vaccine responses, host-associated factors are often neglected. Growing evidences suggest that host factors including age, biological sex, pregnancy, and immune history play important roles as modifiers of influenza virus vaccine efficacy. We hypothesize that host genetics, the hormonal milieu, and gut microbiota contribute to host-related differences in influenza virus vaccine efficacy. This review highlights the current insights and future perspectives into host-specific factors that impact influenza vaccine-induced immunity and protection. Consideration of the host factors that affect influenza vaccine-induced immunity might improve influenza vaccines by providing empirical evidence for optimizing or even personalizing vaccine type, dose, and use of adjuvants for current seasonal and future universal influenza vaccines.

Influenza in High-Risk Hosts—Lessons Learned from Animal Models

“…Seasonal vaccination remains the safest and most efficacious way to prevent influenza infection and reduce disease severity, although not all hosts respond adequately to these preventative measures (Kennedy et al 2012;Green and Beck 2017;Zerbo et al 2017;Dhakal and Klein 2019). Because of the altered immune system in obese models, it is not surprising that the influenza vaccine is less efficacious in obese individuals (Neidich et al 2017).…”

“…Because of the differences in influenza virus immunity and disease severity between age groups, there are age-specific influenza vaccination recommendations worldwide. Because of their short immune history, young children (6 mo to 8 yr of age) in the United States are recommended to receive 1-2 doses of influenza vaccine annually (Neuzil et al 2006;Campbell and Grohskopf 2018;Dhakal and Klein 2019). In the United States and other select countries, a high-dose influenza vaccine is available for those individuals ≥65 yr old.…”

“…Furthermore, the live-attenuated influenza vaccine is not recommended for individuals <2-yr-old or >49-yr-old because of their higher susceptibility to severe influenza virus disease (Grohskopf et al 2018). (The role of host factors in influenza virus vaccination efficacy is further reviewed in Dhakal and Klein 2019. ) Vaccination proves effective in mice with allergic airway disease (Jian et al 2013), but there are limited animal studies defining how other comorbidities impact both vaccination efficacy as well as antiviral efficacy.…”

Application of prophylactic vaccines in the elderly

“…Značajnije promene u genomu virusa, koje nisu tako česte, označene su kao antigenske izmene. One mogu nastati usled rekombinacije genetskog materijala između dva ili više virusa u inficiranim ćelijama ptica ili svinja, kada virus stiče antigenski potpuno novi HA (44,47). Najznačajnije promene nastaju rekombinacijom humanih i životinjskih (najčešće ptičijih) virusa gripa i mogu dovesti do pojave novog i izuzetno virulentnog soja virusa i nastanka pandemija (43,48).…”

“…U njen sastav ulaze, pored dva soja influenca A virusa i dva soja B virusa (50). Budući da virus konstantno menja svoja antigenska svojstva i da sezonska vakcina obezbeđuje samo sojno-specifičnu zaštitu, optimalna zaštita se postiže godišnjom vakcinacijom (47,48). Iz tog razloga, SZO svake godine u februaru (za severnu hemisferu) i u septembru (za južnu hemisferu) daje preporuku za sastav vakcine za nastupajuću sezonu gripa, a na osnovu predikcije koji sojevi će cirkulisati (8,22).…”