Just now, news passed that the trials (phase three) of the vaccine from AstraZeneca (in collaboration with Oxford) have been suspended due to a serious side effect in one of the volunteers. I will remind that it is made based on an adenovirus from monkeys, because half of us already have immunity to human adenoviruses. More about the platforms can be found in a good article (attachment).
With vaccines based on adenoviruses (of any kind), there is also a problem that they will become quite ineffective in a few years in relation to those who received them earlier (irrelevant whether it was COVID-19 or not). After the first vaccination, the body develops immunity against the vaccine itself, so if it worked the first time, it is unlikely to work the second time because the body will kill the vaccine before it can start to work. RNA vaccines (like the one Moderna is making) do not have this disadvantage, but they have another problem: their drawbacks are yet to be seen in the first human trials.
Hi, I'm Rauf Aliev. 