Table 1.
Assessing the interaction between economic classification on the associations between time to the first vaccine and cumulative cases.
| Parameter | Cumulative cases | |||||
|---|---|---|---|---|---|---|
| Crude model | Full model without interaction* | Full model with interaction* | ||||
| β (95% CI) | P-value | β (95% CI) | P-value | β (95% CI) | P-values*** | |
| I. World bank income classifications | ||||||
| Days to vaccine | −0.022 (−0.029, −0.015) | < 0.0001 | −0.006 (−0.012, 0) | 0.0631 | −0.026 (−0.04, −0.012) | 0.0005 |
| Income classifications | ||||||
| Low income | −0.871 (−2.226, 0.484) | 0.2062 | −8.275 (−16.038, −0.511) | 0.0369 | ||
| Lower middle income | −0.186 (−1.168, 0.796) | 0.7087 | −3.905 (−11.022, 3.212) | 0.2801 | ||
| Upper middle income | 0.483 (−0.256, 1.222) | 0.1989 | −12.787 (−19.402, −6.172) | 0.0002 | ||
| High income | — | — | — | — | ||
| Income classifications x days to vaccine | ||||||
| Low income | 0.019 (0.001, 0.038) | 0.0395 | ||||
| Lower middle income | 0.011 (−0.007, 0.029) | 0.2351 | ||||
| Upper middle income | 0.034 (0.017, 0.051) | 0.0001 | ||||
| High income | — | — | — | — | ||
| II. GDP PPP ** | ||||||
| Days to vaccine | −0.006 (−0.012, 0.001) | 0.091 | −0.065 (−0.121, −0.009) | 0.0239 | ||
| GDP PPP | 0.308 (−0.135, 0.751) | 0.1714 | −0.672 (−1.695, 0.351) | 0.1962 | ||
| GDP PPP x days to vaccine | 0.002 (0, 0.004) | 0.0377 | ||||
| III. GDP PPP per capita | ||||||
| Days to vaccine | −0.007 (−0.013, 0) | 0.0464 | −0.033 (−0.056, −0.01) | 0.0048 | ||
| GDP ** | ||||||
| < 7.47 | −0.27 (−1.648, 1.107) | 0.6991 | −10.103 (−20.287, 0.082) | 0.0518 | ||
| 7.78–8.48 | 0.393 (−0.802, 1.587) | 0.517 | −0.035 (−10.884, 10.814) | 0.995 | ||
| 8.49–9.47 | 0.699 (−0.232, 1.629) | 0.14 | −11.037 (−20.924, −1.15) | 0.0289 | ||
| 9.48–10.46 | 0.599 (−0.19, 1.388) | 0.1359 | −12.679 (−21.794, −3.565) | 0.0067 | ||
| >10.46 (Reference) | — | — | — | — | ||
| Days to vaccine x GDP ** | ||||||
| < 7.73 | 0.027 (0.001, 0.053) | 0.0415 | ||||
| 7.74–8.97 | 0.005 (−0.022, 0.033) | 0.7045 | ||||
| 8.98–10.21 | 0.031 (0.005, 0.057) | 0.0181 | ||||
| 9.48–10.46 | 0.036 (0.011, 0.06) | 0.0046 | ||||
| > 10.21 (Reference) | — | — | — | — | ||
GDP, gross domestic product; PPP, purchasing power parity.
*
Adjusted for 2021 population size, median age, and testing data availability (yes/no).
**
Log-transformed.
***
Modeled using multiple linear regression, p-values for t-test unless otherwise indicated.