Although the COVID-19 vaccines have been out for a few years, you may still have questions about how they work, what ingredients are in them and possible side effects.

The information here has been thoroughly researched and backed up by the latest medical science so you can make informed vaccine decisions for yourself and your family.

How COVID-19 vaccines work

The types of COVID-19 vaccines each work a little differently. However, they all produce an immune system response to create the antibodies needed help your body fight off the virus if you encounter it.

Here are the types of COVID-19 vaccines and how they work:

  • mRNA vaccines – This kind of vaccine includes genetic material with specific chemical instructions that tell your body’s cells how to make a small, noninfectious piece of spike protein. The spike protein is how COVID-19 enters the body and how your immune system recognizes it. The Pfizer and Moderna COVID-19 vaccines are mRNA vaccines.
  • Protein subunit vaccines – Subunit vaccines include parts of the virus to stimulate your immune system response. The Novavax vaccine is a protein subunit vaccine that includes harmless proteins from the virus.
  • Viral vector vaccines – This type of vaccine starts with a harmless virus (not COVID-19) and adds a DNA snippet coded with a small noninfectious piece of the COVID-19 spike protein. The Johnson & Johnson vaccine was a viral vector vaccine, but is no longer available.

During the pandemic, the Centers for Disease Control and Prevention (CDC) used a multilayered approach to monitor the effectiveness of the vaccines. Information from these studies has been used to determine the COVID-19 vaccine doses you should get.

The technology behind the COVID-19 vaccines is well established

While the Moderna and Pfizer COVID-19 vaccines are the first to include messenger RNA (mRNA), the technology is far from being new. mRNA technology has been well researched for over 30 years, so development already had a head start. There are a lot of studies to back up exactly what mRNA will do and what it won’t. For instance, it will not permanently reside in your DNA.

The technology behind the Johnson & Johnson vaccine and the Novavax vaccine has been used for other vaccinations. Subunit vaccines are commonly used to prevent conditions such as hepatitis B, shingles and whooping cough. Viral vector vaccines are used for Ebola.

The COVID-19 vaccines don’t change DNA

Here’s how the vaccines work: they send genetic material to our cells – just like blueprints or instructions – that teaches our cells how to defend against the coronavirus. However, the genetic material never enters the nucleus of our cells, which is where our DNA is stored.

That means the genetic material provided by the vaccines as defense instructions against COVID-19 does not interact with or affect our own DNA. Plus, the genetic material from the vaccines is destroyed shortly after it has done its job. There’s no risk to your DNA from the COVID-19 vaccines.

Ingredients that are not in the COVID-19 vaccine

The ingredients used in all the COVID-19 vaccines are safe and routinely used in many other vaccines. Here are a few of the ingredients they don’t include:

  • Live viruses – None of the COVID-19 vaccines contain a live virus. This means you can’t get COVID-19 from the vaccine. The Pfizer and Moderna vaccines don’t contain any virus at all. And the Novavax vaccine only includes harmless proteins from COVID-19. In the Johnson & Johnson vaccine, the inactivated virus was not from the coronavirus.
  • Egg ingredients – Egg ingredients are found in some other vaccines, but not the COVID-19 vaccines. So it’s safe to get a COVID-19 vaccine if you’re allergic to eggs.
  • Fetal cell tissue – There are no fetal cell tissues in the Pfizer, Moderna or Novavax vaccines, and fetal cell tissues were not used in those vaccines’ production and manufacturing processes. There were no fetal cell tissues in the Johnson & Johnson vaccine, but fetal cell tissues were used in that vaccine’s production and manufacturing process.
  • Pork byproducts – There are no pork byproducts in any of the approved or authorized COVID-19 vaccines. So they can be considered kosher and halal.
  • Microchips or other tracking devices – The COVID-19 vaccines do not contain any microchips or other tracking devices.

The facts about COVID-19 vaccine side effects

There’s a lot of misinformation out there about COVID-19 vaccine side effects. The truth is that vaccine side effects are generally mild or moderate, and go away in a few days.

After getting a vaccine, typical side effects include a headache, fatigue and soreness at the injection site. But it’s also possible that you may have no side effects after getting the vaccine.

Severe reactions after the COVID-19 vaccine are very rare. And according to the CDC, benefits of vaccination still outweigh any potential risks. Here’s what you should know about real and rumored side effects:

The COVID-19 vaccine doesn’t cause infertility or miscarriage

There’s no evidence that COVID-19 vaccines affect your current or future fertility or lead to an increased risk of miscarriage.

The vaccines don’t change your body’s DNA or functioning in any way. Instead, they teach your body’s immune system to recognize and fight the coronavirus in case you ever encounter it.

In fact, women who are pregnant are more likely to become severely ill from COVID-19 than people who aren’t pregnant. The CDC recommends all people who are breastfeeding or pregnant get vaccinated against COVID-19.

The American College of Obstetricians and Gynecologists, as well as the Society for Maternal-Fetal Medicine, also recommend pregnant or nursing mothers get vaccinated against COVID-19.

There’s no evidence of any increased health risks – for you or your baby – if you get the COVID-19 vaccine while you’re pregnant or breastfeeding. In fact, research shows that you may pass on protective COVID-19 antibodies to your child.

Severe allergic reactions to COVID-19 vaccines are rare

It’s extremely rare to have a severe allergic reaction (anaphylaxis) to a COVID-19 vaccine, but they can happen. Signs of anaphylaxis include itchy skin, a bumpy red rash, and swollen eyes, lips, hands and feet.

Anaphylaxis usually happens within 15 minutes of getting a vaccine – this is why you’re asked to stick around for a while after receiving it. If you start having signs of anaphylaxis, the provider will be able to quickly respond and call for emergency services, if needed. If you’ve had a severe allergic reaction to a COVID-19 vaccine or are allergic to any of its ingredients, you shouldn’t get that type of vaccine again.

Vaccines don’t cause autism

There is no link between COVID-19 vaccines (or any other vaccine) and autism. This rumor is believed to have begun due to a discredited 1990s research paper. Any link between vaccines and autism has been disproven repeatedly.

Heart problems after COVID-19 vaccination are rare

Rarely, people have developed myocarditis (inflammation of the heart muscle) or pericarditis (inflammation of the tissue that forms a sac around the heart) after receiving the Pfizer, Moderna or Novavax vaccine. Usually, the resulting myocarditis and pericarditis are minor, and people who receive treatment for their symptoms quickly get better.

Depending on your age and gender, your chance of getting this type of inflammation after the COVID-19 vaccine is very unlikely: somewhere between one in 20,000 and one in 100,000.

According to the CDC, myocarditis and pericarditis from a COVID-19 vaccine happen most frequently in male adolescents and young adults after receiving a second dose. But even within this group, the conditions happen very infrequently.

Because the risk is small and the benefits of the vaccine are significant, the CDC still recommends a COVID-19 vaccine for everyone, including young men and people with heart disease.

The Johnson & Johnson vaccine had unique side effects

The Johnson & Johnson vaccine was associated with a couple of potentially serious side effects that weren’t reported with the other vaccines. These included:

  • Guillain-Barré syndrome (GBS) – GBS is a rare medical condition that causes problems with your nervous system, resulting in weakness, numbness, tingling or loss of muscle control. Study data shows that people who received the Johnson & Johnson COVID-19 vaccine had a higher chance of developing GBS. While it’s hard to say for sure that the Johnson & Johnson vaccine caused GBS in these individuals, there have been no cases in people who got an mRNA vaccine.
  • Blood clots – There have been some reports of blood clots after the Johnson & Johnson vaccination. According to the CDC, the problem was rare, happening in four cases per one million doses. However, when blood clots happened, they sometimes caused hospitalization and death.

The final truth about COVID-19 vaccine safety

In the end, the most important message about the COVID-19 vaccines is this: they’re safe, effective and still important. By getting an updated vaccine when it becomes available, you’ll have the best protection against the COVID-19 variants that are currently most common.

While it’s possible to get breakthrough COVID-19 after being vaccinated, getting the COVID-19 vaccine greatly reduces your chance of getting seriously ill. Plus, some research shows that people who are vaccinated are less likely to have long-haul COVID-19 symptoms.