This is easy to say if one is living in the country with all the vaccine supply. Canada bought more doses per capita than any other country, yet US prohibitions on vaccine export meant Canada could not get enough supply in the first few months of the vaccine rollout. A calculated risk was taken to give first doses while waiting for supply to come online, which did eventually happen.
This was not some random experiment on the population. While the gold standard of a phase three trial was not available to support the longer interval, there was plenty of data about the performance of prior vaccines, and interim data about immunogenicity with a longer interval for the COVID-19 vaccines.
No. It is ethical to do that which maximizes life-saving outcomes. Saying that something is an "untested medical intervention" lacks the nuance of saying that some interventions are completely unknown, while others have fairly predictable and understandable effects.
The effects of a single dose were reasonably well understood as well as the impacts on transmission. Reducing transmission is a potentially more relevant goal than individual health outcomes in the grand scheme of things.
While I agree with you on the overall sentiment, it is very hard to apply sometimes. Here in Germany there were a lot of calls to start handing out Curevac doses. They had a few million ready to go, but we were still awaiting trial data.
Our government decided against the emergency usage in the end, and it was the right decision in hindsight, as it turns out that the vaccine is far less effective than its competitors, and could very well have had similar problems as AZ or Biontech.
No one ever claimed that it was the best option, just that it was the only option clinically tested. It would have been irresponsible to recommend a different option without at least some limited clinical trials. Sometimes you can't wait for perfect data.
This was not some random experiment on the population. While the gold standard of a phase three trial was not available to support the longer interval, there was plenty of data about the performance of prior vaccines, and interim data about immunogenicity with a longer interval for the COVID-19 vaccines.