The vaccine contains mRNA; part of the genetic material of the capsule of the virus. 

It does not use any part of the live virus, hence the risk for getting the virus itself is low. 

The most common argument is how quickly it was developed. The answer lies in the method; using the mRNA. Unlike vaccines before which used live or attenuated(weakened form) of the disease this one does not. Early vaccines used live form of the disease. More recent ones used weakened form.  The mechanism for introducing the mRNA into human, would likely be the easier part of the process, since vaccination has been around for centuries, and that has been significantly improved. This is more likely to be the source of side effects or allergies to the vaccine.  Other potential vaccines under development will utilize proteins (again from the capsule) or an inactive component of the virus.

Vaccines work by exposing your body to the antigen (form of the disease) resulting in the creation of an immune response. That is your bodies defense system  (composed of antibodies and white blood cells). Hence subsequent exposure to the virus is likely to result in a shorter duration and lesser intensity of the disease. Take the Flu shot for example. Someone who took the vaccine can still get the flu. However will likely have some minor symptoms for a few days rather than about a week. 

The first  Covid-19 to be approved by the FDA requires 2 doses. Each dose to be administered 3 weeks apart, taking 7 days post inoculation to mount an immune response. There will be side effects from the vaccine. To be clear, occurrence of a true side effect does not automatically equate to a bad vaccine. Sometimes side effects may be the result of an exaggerated immune response. Any  vaccine, drug including the “all natural supplements" taken may result in side effects. Either from the drug itself, its medium or the capsule. The encouraging news is that underlying deciding factor is whether the benefits outweigh the risks. 

• Avoiding exposure to the virus is best way to prevent illness.
• Thought to be spread via person to person contact (within about 6 feet)
• Respiratory droplets in sneezes or coughs from infected persons landing in mouth or nose being inhaled to lungs
• Protect yourself
  • Washing hands with soap and water for at least 20 secs
  • As backup alcohol based sanitizers with at least 60% Completely cover hands and rub until dry
  • Avoid touching eyes, mouths, nose with unwashed hands
• Avoid close contact with sick people
  • Put distance between you and others if Covid-19 is in your community (especially for high risk people)
• Stay home if sick (fever, cough, difficulty breathing)
• Cover when sneezing or coughing
  • With tissue and dispose in trash
  • Inside elbow
  • Immediately wash hands or use alcohol based sanitizers
• Wear facemask if sick when around people
  • If unable cover mouth when sneezing or coughing
• If you’re not sick no need to use facemask unless caring for sick person
• Clean/disinfect surfaces commonly touched
  • Tables, doorknobs, keyboards, computers, toilets, phones, light switches, etc
  • To disinfect
    • Dilute bleach (4 teaspoons per quart of water, or 1/3 cup bleach per gallon of water)
    • Alcohol solution with at least 70% alcohol
    • There is a list of EPA registered household disinfectants

Remember it is transmitted via contact. Placing potentially contaminated items (clothing, bags, purses, suitcases) on your bed or couch after getting home, then taking a shower or washing hands and getting into bed/couch exposes you to the pathogen (virus) via contact.