“…a virus or bacterium) is encountered.) [ [105] , [106] , [107] , [108] ]; - Prior Influenza Infection/Vaccination (effects of prior influenza infection/vaccination on severity of future disease symptoms) [ [109] , [110] , [111] , [112] , [113] , [114] , [115] , [116] ];
- Timing between Viral Exposures (elapsed time between viral exposures) [ [117] , [118] , [119] , [120] ];
- Vaccine-Associated Enhanced Respiratory Disease (where vaccination enhances respiratory disease) [ [121] , [122] , [123] ];
- Chronic Immune Activation (continuous innate immune responses) [ [124] , [125] , [126] ].
…”