How do the 3 new COVID-19 vaccines work?

Last updated: Apr 28, 2021
These shots are the first of their kind, and they’re true medical breakthroughs. Here’s a closer look at the science behind how they were developed.

The fight against COVID-19 has truly been a worldwide team effort. And because of that, the vaccines from Pfizer-BioNTech, Moderna, and Johnson & Johnson are the fastest ever developed.

“Years of research. Tremendous international collaboration. Innovative work by the National Institutes of Health and industry partners. And the inspiring willingness of [thousands of volunteers] combined to allow the delivery of these vaccines in less than a year,” says Helen Boucher, MD. She’s Chief of Infectious Diseases at Tufts Medical Center in Boston.

How were these shots created so quickly? How do they work? Are they safe and effective? Keep reading for the answers to these questions and more.

A new kind of vaccine

The COVID-19 shots developed by Moderna and Pfizer-BioNTech made headlines in December. They were the first to be authorized for emergency use by the U.S. Food and Drug Administration (FDA). But they broke ground for another reason. They’re also the first FDA-authorized vaccines to use mRNA technology. “[This] technology is new but not unknown,” Dr. Boucher says. “It has been studied for more than a decade.” But this is the first time they’ve been used widely in humans. 

The new shots work differently from typical ones. Many vaccines we get use inactive or weakened germs to trigger an immune response. That exposure to the virus or bacteria prepares the body to fight back if you catch the real thing later.

The mRNA vaccines, on the other hand, don’t contain any coronavirus at all. Instead, the shots only carry instructions (mRNA) for creating a part of it called a spike protein. Once you get the vaccine, your body begins to make the viral spike proteins from the mRNA instructions. 

These new spikes don't cause illness. But they do trick your body into building its defenses. The mRNA has a man-made coating that helps it get into cells. It never comes in contact with human DNA and breaks down within hours. Each of the mRNA vaccines requires two doses given three to four weeks apart.

The shot from Johnson & Johnson is called a viral vector vaccine. Instead of using a man-made coating to enter cells, this shot uses a harmless version of a different virus (the “vector”) to deliver the genes that make spike proteins. (In this case, it’s a modified cold virus.) The Johnson & Johnson shot contains short sections of DNA from the COVID-19 virus. They are the parts that code the instructions for making the spike proteins. They cannot make you sick.  

Once the DNA is delivered into cells, it makes mRNA and the rest of the process is like the mRNA vaccines. None of the genetic material gets into the nucleus of cells or ever comes in contact with human DNA. 

Four important notes to remember: 

  1. The cold virus used as a coating in this shot cannot make you sick. 
  2. Only part of the COVID-19 viral DNA is used. It cannot make you sick or change your DNA.
  3. Viral vector vaccines are more temperature stable. They don’t have the same refrigeration requirements as mRNA vaccines.
  4. You need only one dose.

All of the vaccines greatly reduce your risk for getting COVID-19. In the trials, they prevented 100% of hospitalizations for severe COVID-19 and deaths.  

As for those bits of mRNA and the viral vector that set things in motion? Your body destroys both and they vanish. All that’s left is the protection.

The long history of coronavirus research

While it might seem as if these new vaccines appeared out of nowhere, their foundation is deep. For years, labs around the world have been studying vaccines for other types of coronaviruses and other diseases. And mRNA vaccines for several illnesses have been in development for more than a decade. At least four of them have been tested in people.

Early publishing of the SARS-CoV-2 gene map (the name of the virus that causes COVID-19) helped, too. It allowed researchers to quickly find the bits of mRNA or DNA that made the spike proteins to use for the vaccines. 

The same is true for viral vector vaccines. Hundreds of studies have been published since the 1970s, according to the Centers for Disease Control and Prevention (CDC). Most recently, they’ve been used to fight Ebola, and they’re now being studied for HIV, Zika, and flu. 

All that hard work came together in the development of the COVID-19 vaccine, says Christine Turley, MD. She’s the Vice Chair of Research at Atrium Health Levine Children’s Hospital in Charlotte, North Carolina. Dr. Turley also leads STRIVE, a COVID-19 vaccine registry.

“Thirty years ago, we didn’t have the technology to do what researchers are doing now,” Dr. Turley says. “Sometimes people think scientists spend too much time working on things that don’t make a difference. But all that research is making COVID-19 vaccines possible.”

Investing in safety

So how did we get to this point so quickly? “We’ve shortened the timeline tremendously because of investments and advances in science,” says Robert H. Hopkins, MD, chair of the National Vaccine Advisory Committee. 

The U.S. government alone invested billions of dollars. Those efforts were supported by other government agencies, along with private and public institutions and companies worldwide.

“But we have not skipped any critical steps,” Dr. Hopkins says. “We’re doing large trials on human beings. At the same time, companies are building factories, bringing in the raw materials to make vaccines. We’re doing safety and efficacy studies. We’re also preparing to get vaccines out at the same time.”

Both the Pfizer-BioNTech and Moderna vaccines were studied in large trials with nearly 75,000 participants. The Johnson & Johnson trials included about another 40,000. All the studies had extensive outside oversight. 

“Data from [each] were publicly vetted by the FDA and further reviewed by the FDA advisory committee and the CDC,” says Dr. Boucher.

So far, the studies have shown the vaccines to be very safe when compared with the risk of getting COVID-19. Most people have only slight, short-lived side effects after receiving their shots. What’s important to remember if you have any of the common symptoms such as fever, arm soreness, or achiness: “They mean your immune system is responding,” Dr. Turley says. “It’s not a reason to avoid the vaccine. It means it’s working.”

 

The information in this story is accurate as of press time and posting. Getting vaccinated is one of the best ways to limit the spread of the coronavirus. It’s also important to continue practicing social distancing (keeping at least 6 feet away from people outside your household) and washing your hands frequently. You should also be appropriately masked any time you’ll be in public. According to the CDC’s latest guidance, this means layering a disposable mask underneath a snug-fitting cloth mask or placing a mask fitter over your cloth mask to ensure a tight fit. Because the situation surrounding COVID-19 continues to evolve, we encourage readers to follow the news and recommendations for their own communities by using the resources from the CDC, WHO, their local public health department, and our COVID member site

As of April 15, 2021, all Californians age 16 and older are eligible for a COVID-19 vaccine. Find out where to schedule an appointment.

Sign up on My Turn

Related articles

What we know about long-term COVID-19 right now

Here’s what scientists have learned so far about the most common lingering effects and how to manage them.

Removing barriers to getting a COVID-19 vaccine

We are working hard with the state to make the vaccines available to everyone.

Why older adults shouldn’t wait to get a COVID-19 vaccine

Getting vaccinated will help protect you from getting the virus.

Addressing COVID-19 concerns in Pacific Islander communities

We answer common questions those in Pacific Islander communities may have.

Addressing COVID-19 vaccine concerns in Indigenous peoples of America communities

We answer common questions those in Indigenous peoples of America communities may have.

Your simple guide to COVID-19 testing

Discover the differences between the two types of diagnostic COVID-19 tests and learn which one may be best for you.

Concerned? Get the facts about the COVID-19 vaccines

We have answers to common questions about the vaccines.

Your 5-step plan to stay safe with diabetes

Now’s the time to double down on good blood sugar control. But that’s not your only safety measure.

Overcoming needle fears

Does the thought of getting a shot make you want to skip it altogether? Learn how to cope with your anxiety like a pro so you can get the care you need.

6 groups of people who are at higher risk for COVID-19

If you’re an older adult or have underlying conditions, it’s hard not to worry about COVID-19. But knowing the details can help you stay healthy.

Addressing COVID-19 vaccine concerns in Asian communities

We answer common questions those in Asian communities may have.

COVID-19 concerns in Black communities

Addressing COVID-19 vaccine concerns in Black communities

We answer common questions those in Black communities may have.

Addressing COVID-19 vaccine concerns in Hispanic/Latino communities

We answer common questions those in Hispanic/Latino communities may have.

What you need to know about COVID-19 vaccines for teens

Some teens 16 and up are eligible to get the vaccine now.

What to know if you have an ongoing health condition

The vaccines are highly recommended for people with chronic illnesses.

6 great reasons to get the COVID-19 shot

Here’s a look at some of the good things that will happen once you’re vaccinated.

The high-risk people who need the COVID-19 vaccine most

If you’re living with lung disease, hypertension, or diabetes, getting the coronavirus shot is especially important.

Everything you need to know about the COVID-19 vaccines available now

Learn how the three approved shots stack up and find out why all of them can help keep you safe.

Get to know your treatment options for COVID-19

Learn about the latest treatments available for adults and children with mild, moderate, or severe COVID-19.

What does herd immunity from COVID-19 look like?

Learn how getting vaccinated can help us reach herd immunity safely — and get back to living a normal life faster.

A parent’s guide to the COVID-19 vaccine

What you need to know to help protect your child from COVID-19.

5 important COVID-19 vaccine updates for Asian communities

Here are five updates for those in Asian communities about the COVID-19 vaccine.

5 important COVID-19 vaccine updates for Black communities

Here are five updates for those in Black communities about the COVID-19 vaccine.

5 important COVID-19 vaccine updates for Hispanic/Latino communities

Here are five updates for those in Hispanic/Latino communities about the COVID-19 vaccine.

5 important COVID-19 vaccine updates for Indigenous peoples of America

Here are five updates for those in Indigenous peoples of America about the COVID-19 vaccine.

5 important COVID-19 vaccine updates for Pacific Islander communities

Here are five updates for those in Pacific Islander communities about the COVID-19 vaccine.

What everyone with diabetes should know about the COVID-19 vaccines

How long will you wait for a shot? What are the side effects like? Here’s the essential info you need.

Heart disease and COVID-19: Your 5-step plan to help you stay healthy

Now that the coronavirus has your attention, here’s how to help protect yourself.

Protect your community: Meet Dr. Kizzmekia Corbett

Getting vaccinated can help stop the COVID-19 spread in Black communities, which have infection rates three times that of White communities.

Protect your community: Meet Dr. Erica Pan

Getting a COVID-19 vaccine will help stop the spread in at-risk Asian communities.

Protect your community: Meet Virginia Hedrick

Vaccines are important to protecting the health of California’s at-risk Indigenous peoples of America communities.

Protect your community: Meet Dolores Huerta

Getting a COVID-19 vaccine can help stop the spread of the virus in California’s Hispanic/Latino communities.

Protect your community: Meet Dr. Kawika Liu

Getting a COVID-19 vaccine is a crucial step for helping to protect Pacific Islander communities.

Worried about COVID-19 vaccine mandates

We answer your top questions about whether COVID-19 vaccines are (or will be) required, plus how to prove your status.

The future of COVID-19 vaccine research

Here’s what scientists know now about the virus— and what they hope to know soon.