IFNG and infection: Remarkably, though, frequencies of IFN-γ producing cells against the Sp6 and Mp1 subpools were not substantially greater in infected plus vaccinated individuals compared to the other two groups, potentially suggesting that previous T cell immunity to these regions impairs boosting to these regions in response to SARS-CoV-2 or infection, and, in the case of Sp6, after S-based vaccination.