Health Care Access and COVID-19 Vaccination in the United States: A Cross-Sectional Analysis.

BACKGROUND: Although federal legislation made COVID-19 vaccines free, inequities in access to medical care may affect vaccine uptake. OBJECTIVE: To assess whether health care access was associated with uptake and timeliness of COVID-19 vaccination in the United States. DESIGN: A cross-sectional study. SETTING: 2021 National Health Interview Survey (Q2-Q4). SUBJECTS: In all, 21,532 adults aged≥18 were included in the study. MEASURES: Exposures included 4 metrics of health care access: health insurance, having an established place for medical care, having a physician visit within the past year, and medical care affordability. Outcomes included receipt of 1 or more COVID-19 vaccines and receipt of a first vaccine within 6 months of vaccine availability. We examined the association between each health care access metric and outcome using logistic regression, unadjusted and adjusted for demographic, geographic, and socioeconomic covariates. RESULTS: In unadjusted analyses, each metric of health care access was associated with the uptake of COVID-19 vaccination and (among those vaccinated) early vaccination. In adjusted analyses, having health coverage (adjusted odds ratio [AOR] 1.60; 95% CI: 1.39, 1.84), a usual place of care (AOR 1.58; 95% CI: 1.42, 1.75), and a doctor visit within the past year (AOR 1.45, 95% CI: 1.31, 1.62) remained associated with higher rates of COVID-19 vaccination. Only having a usual place of care was associated with early vaccine uptake in adjusted analyses. LIMITATIONS: Receipt of COVID-19 vaccination was self-reported. CONCLUSIONS: Several metrics of health care access are associated with the uptake of COVID-19 vaccines. Policies that achieve universal coverage, and facilitate long-term relationships with trusted providers, may be an important component of pandemic responses.

Aridity shapes cyanogenesis cline evolution in white clover (Trifolium repens L.).

Adaptive differentiation between populations is often proposed to be the product of multiple interacting selective pressures, although empirical support for this is scarce. In white clover, populations show adaptive differentiation in frequencies of cyanogenesis, the ability to produce hydrogen cyanide after tissue damage. This polymorphism arises through independently segregating polymorphisms for the presence/absence of two required cyanogenic components, cyanogenic glucosides and their hydrolysing enzyme. White clover populations worldwide have evolved a series of recurrent, climate-associated clines, with higher frequencies of cyanogenic plants in warmer locations. These clines have traditionally been hypothesized to reflect a fitness trade-off between chemical defence in herbivore-rich areas (warmer climates) and energetic costs of producing cyanogenic components in areas of low herbivore pressure (cooler climates). Recent observational studies suggest that cyanogenic components may also be beneficial in water-stressed environments. We investigated fitness trade-offs associated with temperature-induced water stress in the cyanogenesis system using manipulative experiments in growth chambers and population surveys across a longitudinal precipitation gradient in the central United States. We find that plants producing cyanogenic glucosides have higher relative fitness in treatments simulating a moderate, persistent drought stress. In water-neutral treatments, there are energetic costs to producing cyanogenic components, but only in treatments with nutrient stress. These fitness trade-offs are consistent with cyanogenesis frequencies in natural populations, where we find clinal variation in the proportion of plants producing cyanogenic glucosides along the precipitation gradient. These results suggest that multiple selective pressures interact to maintain this adaptive polymorphism and that modelling adaptation will require knowledge of environment-specific fitness effects.