Let’s examine now the relationship a little more deeply by weighting the smoothing function by total population size as in the above chart. In plain language, India and Ireland no longer carry the same weight when calculating the trajectory of the solid line. Countries with smaller populations are penalized in favor of countries with larger populations.

The weighted estimates between urbanization and vaccination still exhibit a positive relationship but it is no longer monotonously positive. This is largely due to effect of China and India. These are both very large countries, who have despite their large populations managed to outperform their per capita income peers on measures of vaccination).  It should be noted here that China and India are themselves major producers of vaccines, which tends to contribute to vaccination performance. 

In sum, urbanization and vaccination are strongly positively associated. 

• This reflects the common influence of the level of development, which tends to raise both urbanization and vaccination. It also reflects the lesser logistical difficulties to vaccinate everyone in more urban settings.
• There are however two important outliers – China and India – which have overperformed in terms of vaccine coverage relative to their peers and urbanization levels. This, in part, reflects their vaccine manufacturer status as there is an important home bias element in vaccination progress among manufacturers.