The 10 December link you provided is titled "Risk Factors Associated With In-Hospital Mortality in a US National Sample of Patients With COVID-19"
In that report, which is the part you quote, "A randomized, double-masked, placebo-controlled trail (sic) across the United States and parts of Canada26 also concluded that hydroxychloroquine did not help prevent illness when used as postexposure prophylaxis for COVID-19" The 26 represents the citation that I noted, of a report titled "Treatment with hydroxychloroquine, azithromycin, and combination in patients hospitalized with COVID-19" dated 1 July 2020.
26 Arshad S, Kilgore P, Chaudhry ZS, et al; Henry Ford COVID-19 Task Force. Treatment with hydroxychloroquine, azithromycin, and combination in patients hospitalized with COVID-19. Int J Infect Dis. 2020;97:396-403. https://www.ijidonline.com/article/S1201-9712(20)30534-8/fulltext
That cited report, linked as requested, has as the second bullet "According to a protocol-based treatment algorithm, among hospitalized patients, use of hydroxychloroquine alone and in combination with azithromycin was associated with a significant reduction in-hospital mortality compared to not receiving hydroxychloroquine." Which is the opposite of what happened in the JAMA report you posted.
I did not read that entire report, I had to get some work done :) but doing a search for prophylaxis in the "Treatment" article came up with 2 matches, "Currently, randomized trials of hydroxychloroquine for treatment and chemoprophylaxis are underway (NIH, 2020a, NIH, 2020b, NIH, 2020c, Pagliano et al., 2020). Based on these early reports, hydroxychloroquine alone and in combination with azithromycin was incorporated into our institutional clinical guidelines for the treatment of hospitalized patients with COVID-19." and a citation :
Pagliano P., Piazza O., Caro F.D., Ascione T., Filippelli A. Is Hydroxychloroquine a possible post exposure prophylaxis drug to limit the transmission to healthcare workers exposed to coronavirus disease 2019?. Clin Infect Dis. 2020; https://academic.oup.com/cid/article/71/15/887/5811417
This is from 24 March 2020, and this study is actually about using it as a pre and post exposure prophylaxis for health care workers, so this is the report that the article you posted really should have referenced, and it has the following:
"On the basis of these investigations, we believe that hydroxychloroquine can be effective in preventing respiratory tract invasion in HCWs exposed to SARS-CoV-2 and that hydroxychloroquine administration as a prophylactic agent could be particularly useful for HCWs attending to high-risk procedures on the respiratory tract in COVID-19 patients. Hydroxychloroquine’s effectiveness profile, its ability to inhibit lung viral replication for a 10-day period after only a 5-day cycle of therapy, and the large amounts of knowledge in term of safety deriving from its use for malaria prophylaxis and rheumatologic diseases lead us to recommend its preexposure or postexposure use for those performing procedures at high risk of viral diffusion in patients with COVID-19 pneumonia."
Again, I'm not a doctor, but how do you cite a report saying it says one thing when it does not say that at all? The report that they cite is not about using it as a prophylaxis, and the report cited in that report says that it recommends it as a prophylaxis.
I did not get into the actual raw data, so we do not know for the 10 December report that you link when treatment was given or who it was given to. The AMA change is specifically about Phase 1 of the infection, and from what I read in the linked 10 December report it would appear from the verbiage that these were essentially all people who were admitted into the hospital, so most likely Phase 2 and 3 patients, which the AMA also notes in their resolution is where most of the study has been done, and not enough in Phase 1.
More to Baron's point, the cited report from Pagliano et al was available in March and recommends using the cocktail for what would have been Phase 1. This was what many doctors like Baron were advocating for, for their patients, but their ability to use it at their discretion was taken away, for what seems like pure politics. I'm not one of those who believe that everything was nefarious, but when you read through the resolution, it looks like the AMA and the groups they worked with went against everything they stood for when they backed not allowing off label use of these drugs for COVID-19. I do find that disturbing. As an IT professional, that is like me rescinding best practices at my boundary because I found out they don't help against insider threats. I don't know if that makes sense to anyone here, but it's the way I read all of this.