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The Science Behind COVID-19 Vaccines: Parent FAQs

The Science Behind the COVID-19 Vaccine: Parent FAQs The Science Behind the COVID-19 Vaccine: Parent FAQs

​​Many parents have questions about COVID-19​ vaccines, which are currently available to anyone age 12 and up.

Read on for answers to some of the most common questions families may have.

How does the COVID vaccine work?

COVID-19 vaccine works similarly to other vaccines your child has had. Germs such as SARS-CoV-2, the virus that causes COVID-19, invade and multiply inside the body. The vaccine helps stop this by teaching the immune system to recognize and make antibodies to fight the virus. After vaccination, your child has a less chance of getting COVID. And if they do get infected with the virus, including the more contagious Delta variant, they likely will not be as sick as they would without the vaccine.

How are mRNA and viral vector vaccines different?

There are two types of vaccines currently available in the United States: messenger ribonucleic acid (mRNA) vaccines (Pfizer & Moderna), and a "viral vector" vaccine (Johnson & Johnson). They all have the same result — protecting people from COVID-19 — but their delivery systems are a bit different.

  • COVID-19 mRNA vaccines contain nucleic acids, which are the building blocks of all our cells. The mRNA carries instructions inside a lipid coating or fat bubble that tells cells to produce harmless pieces of "spike" protein found on SARS-CoV-2. Once the protein is created, your immune system identifies it as a foreign molecule. The immune process starts, making antibodies that can attach to the virus. These antibodies protect you from getting COVID-19.

    Although widespread use of mRNA vaccines is new, this technology has been studied for decades. mRNA vaccines do not contain any live or dead parts of the virus. Once they’ve done their job, the messenger RNA quickly exits the body. mRNA vaccines are given in a two-dose series. A third dose is now available for certain ​adolescents and adults who have medical conditions or take medicines that weaken the immune system.
  • Viral vector vaccines also give instructions to your immune cells. Instead of carrying the instructions to your cells on a fat bubble, they are carried in a harmless virus which has been modified so it cannot replicate and cause illness (not the coronavirus that causes COVID-19).

    This creates the same process as seen with the mRNA vaccine — the cells create the protein that’s found on the virus that causes COVID-19, the immune system makes antibodies to fight it, and you’re protected from getting COVID-19. The viral vector vaccine available in the United States is given in one dose.

A third type of COVID-19 vaccine, called protein subunit vaccines (Novavax), are in clinical trials and may be considered for emergency use authorization soon. This two-dose vaccine include harmless pieces of the virus that causes COVID-19 to activate the immune system to build protective antibodies.

​How do we know COVID-19 vaccines are safe for kids?

Even before getting FDA emergency use authorization, clinical trials​ showed COVID-19 vaccines to be remarkably safe and effective for adults and teens age 12 and up. Trials involved tens of thousands of volunteers.

The FDA recently gave full approval of the first mRNA vaccine for older teens and adults. Clinical trials for both types of U.S. vaccines are underway for children as young as six months old.

The vaccines continue to be monitored very closely. In fact, the Centers for Disease Control and Prevention (CDC) say that COVID-19 vaccines will have "the most intensive safety monitoring in U.S. history."

Do mRNA vaccines change your DNA?

No, the mRNA does not interact with your DNA at all. DNA is your genetic material and it's stored in the nucleus of a cell. The mRNA in the vaccines never gets into the nucleus. And once your immune cells have used the instructions, they break down the mRNA and get rid of it.

What about side effects of the vaccine?

COVID-19 vaccines are safe, but there are some short-term side effects your child may experience. In clinical trials, some adolescents had no side effects, and some had side effects similar to those reported by adults:

  • Pain, redness, and swelling where the injection was given

  • Fever

  • Chills

  • Headache

  • Fatigue

  • Nausea

  • Pain in the muscles

Call your pediatrician and ask about medicines that can reduce these symptoms, which usually go away in a day or so.

While also rare, some people have had serious allergic reactions to the COVID-19 vaccine. This is why your child will need to wait for 15 to 30 minutes after they have a vaccination. If your child has a reaction, there are medications to quickly treat it.

As for long-term side effects, the CDC says this is unlikely. We have years of research and monitoring on other vaccinations that show side effects almost always happen within six weeks of getting a vaccine.

Are COVID vaccines linked to cardiac issues?

There have been a small number of adolescents and young adults who experienced mild cases of heart inflammation (called myocarditis) after getting the COVID-19 vaccine. However, ongoing research shows that people who became infected with COVID-19 have a greater risk of developing this potential side effect than those who receive the vaccine. (See "Post-COVID Conditions in Children and Teens.")

Distribution of the one-shot, vector vaccine was temporarily paused last spring to look for possible ties to rare but serious blood clots reported during the vaccine’s safety monitoring process. The pause was lifted after data showed the chance of developing the clots with the vaccine is extremely low, but the FDA and CDC continue to monitor this risk.

Is it safe to get the COVID vaccine if I'm pregnant or breastfeeding?

Yes, the American College of Obstetricians and Gynecologists, the American Academy of Pediatrics, and more than a dozen other medical organizations recommend that all pregnant and breastfeeding women get the vaccine. Receiving the vaccine while you are pregnant or breastfeeding will protect you, and also pass along protective antibodies that may help protect your baby.

Can COVID vaccines affect fertility?

There's no evidence that any vaccine, including those for COVID-19, causes fertility​ side effects. The vaccines don't affect puberty or a child's reproductive development in any way. It is safe for pregnant women and anyone who wants to become pregnant in the future. In fact, among the millions of people now immunized, there are women who got the COVID-19 vaccine while pregnant and women who became pregnant after getting it. Doctors have watched these cases closely, and have reported no safety problems.

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American Academy of Pediatrics (Copyright © 2021)
The information contained on this Web site should not be used as a substitute for the medical care and advice of your pediatrician. There may be variations in treatment that your pediatrician may recommend based on individual facts and circumstances.
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