Why people would assume (with rock solid conviction in a lot of cases) that all vials contain the same thing is beyond me. When they did the 'tetanus' covert sterilization in Kenya recently it is said that a fraction of the vials come from a specialty lab in Canada while others seemed to have come from a factory.
thats called bad batching.
there is actually processes in place that monitor different batches whether its the same lab/factory, but just in a different production slot. or from different labs/factories.
they actually sample random vials within a batch and see if a batch is good or not.
its not just vaccines. heck even meat pie industry regularly test their batches.
they may make 1000pies an hour. so every 30 minutes they take a pie and test it for weight/ filling amount. they test for bacteria and also if the pastry rose to the right height and the temperature is right.
they dont simply just let the machines run all day and only check once the machines alarm beeps.
when it comes to medical supply checks. they do loads of stuff. far beyond what a food production factory world.
yes some kenyan citizens might be blackmarket selling 'vaccine' where the supplier used could have been a ethiopian 'sweatshop' counterfit factory putting river water into vials instead of vaccine
yes bad batches can happen.
but for instance with these vaccines they are being sourced via the companies direct. they are setting up logistics and distribution to get it from source.
yes 9 months ago there were cases where america were in a rush to source PPE and trumps son inlaw was just handing out money to whomever said they can supply PPE. and yes plane loads of PPE arrived. and on inspection they found out it didnt meet standards. and so trumps son inlaw was taken off that project and it was handed to pence.
so yes bad batches can happen if idiots are in charge of the logistics and dont source the products from a trusted source thats been vetted properly.
so yes batches can be a problem. but the chances of a bad batch getting to a destination to then be handed out to citizens is super super low due to the different checks/layers of inspection inbetween