In QED, the Lagrangian has a term $\bar{\psi}A^\mu\psi$, which gives a correction to the photon propagator, where the loop is made of a pair electron-positron, with the 1st order diagram:

[![electron loop](https://i.stack.imgur.com/CVbwH.png)](https://i.stack.imgur.com/CVbwH.png)

In the Standard Model, there are also couplings such as $\bar{u}A^\mu u$ and $\bar{d}A^\mu d$, which would give rise to a similar correction (changing mass and dividing the coupling by 3). but I have never seen this discussion in a QFT textbook. Isn't this correction important? Wouldn't it change how we measure the vacuum polarization? The electron mass is $\sim0.51$MeV while the up quark mass is $\sim2.2$MeV, so it isn't heavy enough to be ignored.

One reason I thought could explain this is that the range of electromagnetic interactions is much larger than that of the strong force, so the quark-antiquark pair would hadronize before they could annihilate, but I'm not completely convinced this is true. Can anybody shed a light on this?