I note that the parent doesn't attempt to provide a summary. I'm no immunologist but it seems to me that this study examines a third-order consequence (levels of IFN-gamma in whole blood samples) to infer a second-level consequence (levels of CD4 helper and CD8 cytotoxic T-cells, which are secreting the IFN-gamma), which is presumed to be indicative of a root-level occurance ("a detrimental effect in the overall magnitude of the spike-specific humoral response in COVID-19 recovered individuals"). It's not clear to me how the second order consequence clearly implies the root-level occurance.
This [0] is the paper in the fifth citation from the parent's article. It seems to come to similiar conclusions, but, like the parent's article, doesn't assess any real world data, just lab conditions and inferences.
I urge everyone reading this to remind themselves of the specific language used in these articles -- they don't actually know whether these correlates they're observing are affecting immunity, just one component of what we consider to be a single aspect of an appropriate immune response in a blood sample.
Does my linked article, above and in a different thread, also measure blood sample conditions? Absolutely. But the article I linked directly analyses (spike protein) antibody levels -- an appropriate immune response in a blood sample -- while the articles here examine inferred T cell presence. One is a direct measure of something straightforward, and the other an inferential examination of something complex.
[0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7885942.1/