(CBSDFW.COM) – The first round of patients participating in Pfizer’s COVID-19 vaccine study got their doses on Wednesday in North Texas.

Researchers at North Texas Infectious Disease Consultants gave out shots to participants — most of whom are essential and front line workers including medical personnel. The shots are given out to those who signed up to be part of the study.

Dr. Mezgebe Berhe, an infectious disease specialist, says such studies are important to test the safety of the vaccine. “Preliminary data shows the vaccine is relatively safe,” Dr. Berhe said. “It induces a good immune response and we are doing this last phase of the trial to see actually if we can prevent disease.”

The study includes more than 30,000 participants from ages 18 to 85. It is in its phase 3, or the final phase, before the results are sent for FDA approval.

So far, the vaccine shows promise – Pfizer has reported only mild side effects such as fever, fatigue and chills, and no serious adverse events.

Moderna, the other company testing a COVID-19 vaccine, is also in its final phase of testing. Pfizer says it hopes to presents its findings to the FDA by October 2020 and plans to supply 100 million doses by the end of 2020. Here’s how you can take part in the trial.