Scatter plot matrix of the agreement between the estimated overall log odds ratios produced by the fixed effect methods that include double-zero-event studies. I5, inverse-variance method with 0.5 continuity correction; ITACC, inverse-variance method with treatment arm continuity correction; IEMP, inverse-variance method with empirical continuity correction; MH5, Mantel–Haenszel method with 0.5 continuity correction; MHTACC, Mantel–Haenszel method with treatment arm continuity correction; MHEMP, Mantel–Haenszel method with empirical continuity correction.