It has been 4 weeks after my Superday interview— still haven’t heard back from HR?

Had an Superday interview at a large/international bank for credit and wholesale banking summer analyst position in New York City 4 weeks ago (beginning of December,2019). I got interviewed on Friday and reached out to HR on the following Monday about my application. I also sent thank you notes to my interviewers on the same day, and one of them replied. HR replied on same day telling me that I will hear back in approximately 2 weeks. Two weeks pass by and I havent heard from HR, so I send them another email (a day after Christmas— horrible timing, I know), still no reply. Today officially marks the end of fourth week mark after my Superday interview, and it is still only 4 days after New Years. Given the “end of year” crunch and the back to back holidays, I’m assuming that the banks are extremely busy. I just don’t know how/when the best time to reach out to HR is. Should I just assume that I have been rejected? What should I do? Do superday interviews usually send out rejection letters?

Any advice would be appreciated. Thanks!