Extended Data Fig. 2: Additional subgroup analyses for comparison of pooled intervention letter group vs. usual care.

We tested for effect modification across additional subgroups for the comparison of all intervention arms pooled vs. usual care. Estimates are absolute differences in percentage points with error bars representing 99.29% confidence intervals from binomial regression models with household-level clustered standard errors, identity link, and interaction terms, from which interaction p-values were also derived. Interaction p-values < 0.05 were considered nominally statistically significant. Presence of at least one chronic disease was defined as chronic lung disease, diabetes, chronic cardiovascular disease, cancer, chronic kidney disease, immunodeficiency, neurological/neuromuscular disease, liver disease and/or rheumatic disease. CI, confidence interval.