Delays and declines in seasonal influenza vaccinations due to Hurricane Harvey narrow annual gaps in vaccination by race, income and rurality.

OBJECTIVE: Temporal overlap of the Atlantic hurricane season and seasonal influenza vaccine rollout has the potential to result in delays or disruptions of vaccination campaigns. We documented seasonal influenza vaccination behavior over a 5-year period and explored associations between flooding following Hurricane Harvey and timing and uptake of vaccines, as well as how the impacts of Hurricane Harvey on vaccination vary by race, wealth, and rurality. DESIGN: Retrospective cohort analysis. SETTING: Texas counties affected by Hurricane Harvey. PATIENTS: Active users of the Veterans' Health Administration in 2017. METHODS: We used geocoded residential address data to assess flood exposure status following Hurricane Harvey. Days to receipt of seasonal influenza vaccines were calculated for each year from 2014 to 2019. Proportional hazards models were used to determine how likelihood of vaccination varied according to flood status as well as the race, wealth, and rural-urban residence of patients. RESULTS: The year of Hurricane Harvey was associated with a median delay of 2 weeks to vaccination and lower overall vaccination than in prior years. Residential status in flooded areas was associated with lower hazards of influenza vaccination in all years. White patients had higher proportional hazards of influenza vaccination than non-White patients, though this attenuated to 6.39% (hazard ratio [HR], 1.0639; 95% confidence interval [CI], 1.034-1.095) in the hurricane. year. CONCLUSIONS: Receipt of seasonal influenza vaccination following regional exposure to the effects of Hurricane Harvey was delayed among US veterans. White, non-low-income, and rural patients had higher likelihood of vaccination in all years of the study, but these gaps narrowed during the hurricane year.

Population-environment drivers of H5N1 avian influenza molecular change in Vietnam.

This study identifies population and environment drivers of genetic change in H5N1 avian influenza viruses (AIV) in Vietnam using a landscape genetics approach. While prior work has examined how combinations of local-level environmental variables influence H5N1 occurrence, this research expands the analysis to the complex genetic characteristics of H5N1 viruses. A dataset of 125 highly pathogenic H5N1 AIV isolated in Vietnam from 2003 to 2007 is used to explore which population and environment variables are correlated with increased genetic change among viruses. Results from non-parametric multidimensional scaling and regression analyses indicate that variables relating to both the environmental and social ecology of humans and birds in Vietnam interact to affect the genetic character of viruses. These findings suggest that it is a combination of suitable environments for species mixing, the presence of high numbers of potential hosts, and in particular the temporal characteristics of viral occurrence, that drive genetic change among H5N1 AIV in Vietnam.

Spatiotemporal structure of molecular evolution of H5N1 highly pathogenic avian influenza viruses in Vietnam.

BACKGROUND: Vietnam is one of the countries most affected by outbreaks of H5N1 highly pathogenic avian influenza viruses. First identified in Vietnam in poultry in 2001 and in humans in 2004, the virus has since caused 111 cases and 56 deaths in humans. In 2003/2004 H5N1 outbreaks, nearly the entire poultry population of Vietnam was culled. Our earlier study (Wan et al., 2008, PLoS ONE, 3(10): e3462) demonstrated that there have been at least six independent H5N1 introductions into Vietnam and there were nine newly emerged reassortants from 2001 to 2007 in Vietnam. H5N1 viruses in Vietnam cluster distinctly around Hanoi and Ho Chi Minh City. However, the nature of the relationship between genetic divergence and geographic patterns is still unclear. METHODOLOGY/PRINCIPAL FINDINGS: In this study, we hypothesized that genetic distances between H5N1 viruses in Vietnam are correlated with geographic distances, as the result of distinct population and environment patterns along Vietnam's long north to south longitudinal extent. Based on this hypothesis, we combined spatial statistical methods with genetic analytic techniques and explicitly used geographic space to explore genetic evolution of H5N1 highly pathogenic avian influenza viruses at the sub-national scale in Vietnam. Our dataset consisted of 125 influenza viruses (with whole genome sets) isolated in Vietnam from 2003 to 2007. Our results document the significant effect of space and time on genetic evolution and the rise of two regional centers of genetic mixing by 2007. These findings give insight into processes underlying viral evolution and suggest that genetic differentiation is associated with the distance between concentrations of human and poultry populations around Hanoi and Ho Chi Minh City. CONCLUSIONS/SIGNIFICANCE: The results show that genetic evolution of H5N1 viruses in Vietnamese domestic poultry is highly correlated with the location and spread of those viruses in geographic space. This correlation varies by scale, time, and gene, though a classic isolation by distance pattern is observed. This study is the first to characterize the geographic structure of influenza viral evolution at the sub-national scale in Vietnam and can shed light on how H5N1 HPAIVs evolve in certain geographic settings.