Vaccine Basics

You Have Questions… Let’s Talk About Them!

Yes, it was created quickly – but scientists have been working on this technology for 10+ years. Scientists all over the world worked together and shared information to create the COVID-19 vaccines. 

The COVID-19 vaccines were tested with tens of thousands of people to make sure they meet safety standards and protect adults of different races, ethnicities, and ages. Millions of people have already safely received one of the three COVID-19 vaccines available – Pfizer, Moderna, and Johnson & Johnson. Vaccine safety is continuously monitored. 

First of all, you can’t get COVID-19 from the vaccine. But after you get the vaccine, you could have some side effects. These side effects include headaches, feeling tired, or having a stomachache. The most common side effect is feeling sore or swollen where you got the shot. These side effects are normal! They are signs that your body is building protection. These side effects may be unpleasant for 1-3 days, but they are not dangerous.

The Johnson & Johnson vaccine, however, has recently been associated with some rare adverse effects; if you have received the J&J vaccine within the past 3 weeks and experience symptoms such as severe headache, abdominal pain, leg pain or weakness, or shortness of breath, you should contact your healthcare provider right away. Risks for severe outcomes are higher in women 30-49, but are present for both men and women in all age groups as well.

If you don’t have side effects, don’t worry – your body is still building protection. Some people just react differently.



Yes. You should get the vaccine even if you have already had COVID-19. Some people have gotten COVID-19 more than once. The vaccine also offers more protection against reinfection than your body could develop on its own from already having COVID-19.

While most people who get COVID-19 recover, some develop serious health issues that can affect them for a long time.By getting the vaccine, you lessen your risk of getting sick or being hospitalized with COVID-19. You also are helping to reduce spread of COVID-19.

The Pfizer-BioNTech and Moderna COVID-19 vaccines both require two shots. For these vaccines, it is important to get both shots in order to gain the most protection. Before you leave the vaccination site, make an appointment to get the second shot 3-4 weeks after the first shot, depending on the vaccine. This is the best time to get your second shot if you can.

The Johnson and Johnson COVID-19 vaccine requires only one shot, but is not the vaccine preferred by the CDC, which advocates that people receive an mRNA COVID-19 vaccine (Pfizer-BioNTech or Moderna).

Some people may also qualify for a booster dose. Learn more about boosters here.

Yes. The COVID-19 vaccine is free to everyone, regardless of insurance or immigration status. When you go to get your vaccine, you might be asked for your insurance card or your Medicaid or Medicare information. Why? The place where you are getting the vaccine might charge a small fee to your insurance company or the government. This charge cannot be passed on to you. You cannot be denied a vaccine if you do not have insurance. If you don’t have insurance, Medicare, or Medicaid, just say so. You still get the vaccine for free. For some vaccine events, you might be asked to bring proof of residency, but government-issued ID is not required.

Chicago Star Chicago Star Chicago Star Chicago Star


No steps are skipped during the clinical trial process for COVID-19 vaccine.

  • The FDA authorizes vaccines after they pass three phases of clinical trials
  • These clinical trials require thousands of people and months of data
  • The vaccine development is faster than normal because some steps are being done at the same time instead of one after another

Vaccine safety checks are in-progress and will continue as long as a vaccine is available.

  • When a vaccine trial is paused or cancelled, it is normal and means the safety checks are working
  • Vaccine recalls are rare. If a recall is issued, the FDA and CDC will let health officials and the media know immediately
  • After the vaccine is authorized, FDA and CDC will continue to monitor it using three federal safety systems that are already in place

Early studies have shown the vaccine is still effective against COVID-19 variants.

  • Evidence suggests that variants can spread more easily but there is no evidence that the new strain affects the sensitivity of diagnostic tests or that it causes more severe illness or increased risk of death

  • Data suggest current vaccines will be effective and safe in providing protection against the variant

Chicago Star Chicago Star Chicago Star Chicago Star

Benefits of Getting COVID-19 Vaccine

COVID-19 vaccination will help keep you from getting COVID-19.

  • Getting a COVID-19 vaccine may help keep you from getting seriously ill even if you do get COVID-19.
  • Getting vaccinated yourself may also protect people around you, particularly people at increased risk for severe illness from COVID-19.

COVID-19 vaccination will be a safer way to help build protection

  • COVID-19 can have serious, life-threatening complications, and there is no way to know how COVID-19 will affect you. And if you get sick, you could spread the disease to friends, family, and others around you.
  • Getting COVID-19 may offer some natural protection, known as immunity. But experts don’t know how long this protection lasts.
  • The risk of severe illness and death from COVID-19 far outweighs any benefits of natural immunity. COVID-19 vaccination will help protect you by creating an antibody response without having to experience sickness.

COVID-19 vaccination will be an important tool to help stop the pandemic.

  • Stopping a pandemic requires using all the tools we have available. Together, COVID-19 vaccination and everyday preventative actions will offer the best protection from COVID-19.
  • Wearing masks and social distancing help reduce your chance of being exposed to the virus or spreading it to others, but these measures are not enough. Vaccines will work with your immune system so it will be ready to fight the virus if you are exposed.

For more information, see Facts about COVID-19 vaccines.

Chicago Star Chicago Star Chicago Star Chicago Star

mRNA Vaccines

Two vaccines were developed using a new vaccine technology employing messenger RNA (mRNA).
  • mRNA vaccines are being held to the same rigorous safety and effectiveness standards as all other types of vaccines in the United States. The only COVID-19 vaccines the Food and Drug Administration (FDA) will make available for use in the United States (by approval or emergency use authorization) are those that meet these standards.
  • mRNA vaccines cannot give someone COVID-19. They do not use the live virus that causes COVID-19.
  • mRNA vaccines do not affect or interact with our DNA in any way. mRNA never enters the nucleus of the cell, which is where our genetic material (DNA) is kept. The cell breaks down and gets rid of the mRNA soon after it is finished using the instructions.

Chicago Star Chicago Star Chicago Star Chicago Star

Vaccine History

Vaccinations have saved hundreds of millions of lives over the last century. Scientists have developed vaccines for Smallpox, Polio, Measles, Mumps, Rubella, Hepatitis, Meningitis and more. The WHO considers vaccine development one of the greatest global health achievements.