It all comes down to trust, and to some degree what is reasonably logical. I'm not a believer of conspiracy theories, flat earth or anything, I'm just saying this so that nobody thinks that I do believe in that with what I'm about to write.
How do we know ANYTHING? For example, have ANYONE here in this forum, actually seen that the earth is a globe with their own eyes? I've not, I've only seen the pictures in school and on the Internet. And obviously, there IS NO WAY for ANYONE making fake photos(Sarcasm). Or how does anybody know that for example Columbus actually existed? Because someone in a book wrote the history? Well NOBODY has ever written anything fake(sarcasm).
So how do we "know" these things? How do we know that the Earth isn't flat? Because it's logical (I won't go into the scientific discussion and all that). There are some things in life you just have to trust when it is reasonable and logical.
So how can we be sure that the vaccines are "safe"?
Well, we can't, we just have trust that it's the most reasonable and logical thing to trust that the actually do more good than harm.
And just as some others have commented already. Where do you think other vaccines have been manufactured? Wouldn't be so surprised if vaccines "Made in the US or in Europa" was developed in those parts, but manufactured in factories in India or chine (because of the labour costs).
And also suggesting that you should distrust China more just because it's China, just seems a bit racist. Why should you trust the Chinese government more than for example US/Europe? Is there any "proof" that the Chinese government lie more/less than US/Europe governments?
"Power tends to corrupt, and absolute power corrupts absolutely."
This is not only true for "3rd world" countries, but for ALL men who have power.
And just as a sidenote.
If you weren't aware of it, anytime you take any new medicine, even if it has been around for decades, you are still a guineapig. Because we are all different, so just because 1 billion people using a certain medication has never had a side effect, it doesn't mean that YOU won't. You just have to outweigh the benefits vs the risks.
And it wouldn't surprise me that although it is a personal choice to take the COVID vaccine or not, if you've not taken it when you'd had a chance and then later gets sick with COVID, the health/government officials, will just say: "Sorry, we won't treat you, you had your chance of getting the vaccine, so now you have to face the consequences". That or any other absurd policies.