How to get x-amzn-oidc-data in Expres/NodeJs backend with ALB and Cognito?

Question

I have setup and application which uses a React front-end and Expres/NodeJS back-end. There is an ALB in the mix as well. So, here is how the flow goes:

The ALB listens on port 443 and there is an Authentication action attached to the listener. This action uses and Amazon Cognito user pool, scope is openid. Once the authentication is successful the ALB redirects the request to the React app which in it's turn sends http requests back to the ALB which redirects them to the Express app on the server-side. I have setup the communication between FE and BE like this because we use Amazon ECS and I don't have a static DNS or IP except for the ALB.

I am unable to get the x-amzn-oidc-data header when console logging the req.headers. This header is important to me because I'd like to verify and work with the JWT that it contains. I have read most of the docs on the Internet and they say that the ALB automatically sends this header (and couple of others) to the back-end. However, I only see one x-amzn-trace-id which has nothing to do with the JWT issued by Cognito.

Where do you think is my error? My setup seems pretty standard to me - how could I get that header?

Thanks in advance!