You already know the difference: "I" is missing in CA.
CA: Contrastive Analysis (contrastive linguistics, or cross-linguistic contrast) is concerned with different native languages (L1).
CIA: Contrastive Interlanguage Analysis is clearly about the learner' interlanguage - their knowledge and production of the second/foreign language being learnt (L2).
Constrastive Analysis in SLA is a systematic methodology, but CIA is not as strong as CA. One thing we can be sure is that CIA is a sub-category of CA.