Odds ratios with unadjusted 95% confidence intervals for selected exposure variables, testing associations with low anti-Spike antibody levels, for sub-samples of TwinsUK (purple circles) and ALSPAC (red diamonds) individuals tested in Q2 or Q4, while single-, double-, or triple- vaccinated. Low antibody levels were defined as the lowest 10% within the given sub-sample, except for ALSPAC and TwinsUK Q2 double-vaccinated sub-samples where lowest 8% is used due to assay upper limit. Each point estimate originates from a distinct multivariate logistic regression model, including the exposure variable of interest and adjustment variables of age, sex, name of most recent vaccine received and weeks since most recent vaccination. Note x-axis ranges on sub-plots vary, and vaccine received panel uses a logarithmic x-axis. Odds ratio = 1 is indicated with a dashed black line.