Don't understand why those Guess those professional are not including Zinc in their treatment also.
I have not had the time to go over all the comments in this thread or go over the original articles from the mentioned studied but I will make one point. There is also an epidemic of medical "experts" on the internet. I do not mean that as a derogatory term but people need to realize what it takes to become a real expert:
4 years of undergrad with average GPA 4.0 or A+, volunteering, research, and leadership roles
4 years of medical school
At least 2 years of residency
Now those people who you see in the studies also likely have an additional 3 years of residency for ID or publichealth, they likely have an additional 1-2 years of fellowship and likely 2-3 years additional for their graduate training. That is 18 YEARS of studying before they are named experts on the field.
I would also like to point out that the academic ID experts who I quoted to have approximately 18 years of experience usually are not motivated by money. They infact take a pay cut to do what they do. Most of them are salary and do research because they love doing it. If they were after money they would be fee- for service and they would not do graduate school. In fact if money was their sole interest opening a medical spa and selling HCQ, Zinc, Azithro would probably make them millions.
So what does all that training give those experts which an online overnight expert does not have when it comes to this topic?
A) Understanding of the pathophysiology and pharmacology
B) Critical thinking and appraisal skills
C) Knowing the CONTEXT and history behind things
So taking those points and applying it to your question of why zinc was not included:
A) Synergistic drug effects are VERY rare in medicine. One of the few examples is levo dopa for parkinsons and that has a clear relationship. For one drug to make another drug better it has to alter its mechanism of action; otherwise that drug is just a cofounder and including it in the study is just adding noise to the impact of the drug of interest. Azithro is included in the HCQ regimen because it is an antibiotic and its sole purpose is to try to prevent opportunistic infections from a diseased COVID lung, it does nothing against COVID and it does nothing with HCQ. Zinc it self has immune properties. HCQ has a very complex multi progned mechanism that people dont really understand thats why it is tried literally in all diseases.
B) It is VERY hard to show that a drug has an impact unless it is very clear like vaccines are and even that is debated... lol. To show in a study that a specific drug is the REASON why someone got better and it was not just chance alone, the natural history of the disease or any other supportive intervention or patient protective factor is a BIG task. The only way is a randomized double blinded, placebo control trial with BIG numbers to make inferences from a sample to a population. Having more drugs only makes things harder for the investigators at some point if the claim is HCQ works people have to isolate it and do combination studies
C) This is perhaps the most important. People that study mediicne know how these trials go and know about HCQ. There is always chaos at the begining of every drug. If you take a sugar pill and claim its a cure to cancer I am sure you will get mixed results from actual researchers, just due to chance alone 5% of studies will be positive no matter what given the significance value of 95% used in medicine. The other important factor is experts KNOW what is relevant when treating a patient. A drug may have a clear established effect but whats the point if it has no clinical impact? You need experience to know these things.