Um not really. The big risks are hypersensitivity reaction for killed vaccine and infection, of course, for live vax candidates. Live vax candidates are uniformly tested on lab animals before people. However, this isn't necessarily the biggest obstacle to vax development.
The reason vax development takes so long is that is that it can take up to 6 months to determine if the vaccine (+/- boosters) produces a durable population of B-cells that produce immunizing antibodies. Here's an example of what the immune response to a vaccine looks like (with a booster) :
Because of the lag between vaccine and immune response, there is a necessary amount of time that has to elapse to see if it produced the desirable effect. This gives you hard limits on how long it takes you to answer questions about efficacy, etc. There are of course other things to be done like scale up manufacture of the vaccine in a GMP facility, etc, but the length of time it requires to produce a durable immune response is why it will take a while to see if a vaccine works or not.