I will try...

Vaccines are studied by researchers from different affiliations, and published in peer-reviewed journals. Such studies require multiple stages, and when a vaccine is considered ready for the public, its side effects are already known.

Big pharma is corrupt, but their main goal is money, and they get A LOT of money from selling vaccines. In the unlikely event of one company frauding a vaccine, this would be such a scandal that would affect its commercial relations in the entire world, thus, generating less profit in the long run and making investors move to other companies.

The government is corrupt, but they want the population to be healthy enough to work, pay taxes and contribute to gdp. Giving room for simple diseases to kill people goes totally against the government's goals.

Remember, neither governments or companies want people to die, and curing lethal or disabling diseases goes in their own interests. Besides, we already have lots of chronic diseases and conditions around to continuously sell medicine.

There's no reason for any involved party to create fake vaccines and give it to people. If you're really unsure, I recommend contacting universities and asking about assessment programs ( I don't know how that would be called in english), because some places test samples from vaccines that will be used, in order to check if everything is ok. They probably publish the results too, and they're not only experts in the field, but are independent parties.

I hope this was of some help.