Sure it is. It has to be. Nobody is an expert in everything. For the modern world to exist we have to replace direct experience with a web of trust in each other. We have to believe in each other.

Science as a process comes with a lot of checks and balances, GLP and QA/QC and peer-review are some of the names of the formal and informal systems that surround the bare process of science. No one peer-reviews every journal even in a single field, audits every medical lab or examines the medical error rates at multiple facilities. You have to trust that people are doing those things, and that they're competent at them. If you care to look, there will be details and information to cover all the details, but even in an entire lifetime a single individual will not have enough time to examine even a year's worth of that volume of information.

You can chose not to believe, but one person could not have developed the vaccine in less than a few decades of work on their own.