Article Figures & Tables
Tables
- Table 1:
Population-related factors affecting evaluation of vaccine efficacy in endemic versus pandemic states of infection and those unique to coronavirus disease 2019
Factors affecting demonstration of vaccine efficacy Endemic state of infection Pandemic state of infection COVID-19 unique factors Strategies Baseline transmission of target pathogen in population (i.e., exposure) and its seasonality Known Rapidly changing; seasonality unknown Social distancing and other public health interventions Flexible trial designs to ensure adequate numbers of end points (infections or hospital admissions); determination of potential confounding by nonvaccine prevention measures Population level of pre-existing immunity to target pathogen (i.e., susceptibility) Known Rapidly changing Paucity of seroepidemiologic data; accuracy of serologic tests; unclear extent and duration of protection from natural immunity Baseline serologic testing of participants in efficacy trials Differential susceptibility of subpopulations to infection or disease Known Emerging Numerous risk factors identified, but older adults at highest risk of severe disease; young children rarely have complications and may be less susceptible to infection; antibody-dependent enhancement Evaluation of vaccine efficacy and end points in older adults and other high-risk groups; close monitoring and prolonged follow-up for possible antibody-dependent enhancement in all trials Note: COVID-19 = coronavirus disease 2019.