KNOXVILLE, Tenn. (WATE) – The largest nationwide vaccination plan since polio is getting underway this week as the U.S. prepares to vaccinate more than 328 million Americans against SARS-CoV-2, the virus that causes COVID-19.

If you’re thinking about getting vaccinated, here are some things that the Knox County Health Department and other health leaders need you to know.

The Moderna vaccine will be administered in Knox County, according to Dena Mashburn, director of nursing for the Knox County Health Department. This vaccine is expected to gain FDA approval by the end of this week. Vaccine will arrive in small batches trickling in over the next few months and plans are in place to begin immunizations shortly after it arrives in Knoxville.

Both vaccinations must come from the same company. If you take the Moderna vaccine in your first shot, the mandatory follow-up shot three weeks later must also be the vaccine made by Moderna. You cannot mix and match. So it’s a good idea to ask (and write down) who the manufacturer is when getting vaccinated.

Vaccinations will be given in two doses that are 21 days apart. If you miss that deadline, health officials say to get it anyway. And if you know you’re going to be later than 21 days, try to get it earlier.

Whether or not to get the vaccine is your choice. But beware, some businesses may require it.

“The vaccine is voluntary and a personal decision for everyone,” Mashburn said.

People will likely experience side effects of the vaccine. Health officials say people could experience chills, fatigue, headache, or fever, especially after getting the second vaccination. During trials for Pfizer’s vaccine, people under 55 years old reported experiencing these effects more than those who are older.

Mashburn said the volume of misinformation is “overwhelming” about the vaccine. She suggests that those searching for information on the vaccine use trusted sources like your personal physician, the Knox County Health Department, the Tennessee Department of Health, the Centers for Disease Control and Prevention, and the World Health Organization.

If you’ve had COVID-19, you still need to get vaccinated.

Vaccines will be administered as a shot into the arm. That’s the only method available at this time.