There’s been so much buzz about the new COVID-19 vaccines, and it’s understandable since everyone is hopeful they could bring an end to the pandemic. So far, two vaccines—by Pfizer-BioNTech and Moderna—have been approved in the U.S., and another one, developed by Oxford-AstraZeneca, will likely be approved soon. They all have similarities in that they aim to protect the human body from COVID-19, but they’ll all different in their own ways, too.

Health officials, including Dr. Anthony Fauci, have said 75% to 85% of Americans need to get vaccinated to achieve herd immunity and eliminate coronavirus. According to the Pew Research Center, 60% of U.S. adults would “definitely” or “probably” get the coronavirus vaccine, but 21% say they won’t get vaccinated and having more information isn’t likely to sway them.

Still, medical experts emphasize the safety of the COVID-19 vaccines. Dr. Daniel Fagbuyi, MD, an emergency room physician and an Obama administration biodefense and public health appointee, says everyone needs to understand the risk-benefit ratio. “When we say safe, we’re referring to the fact that the benefits outweigh the risks,” he explains. “So, basically, we think the benefits of you getting the vaccine outweigh the risk of getting COVID.”

So, how do the different vaccines compare? asked experts to explain.

Pfizer and Moderna vaccines work in the same way

The vaccines developed by Pfizer-BioNTech and Moderna were given emergency authorization by the U.S. Food and Drug Administration in December. They use similar technology, known as mRNA, which Dr. Fagbuyi calls a “new school” way of creating vaccines, though he says scientists have been researching the technology for more than a decade.

mRNA, or messenger RNA, vaccines direct the body’s cells to make a “spike protein,” which is found on the surface of the virus causing COVID-19, according to the Centers for Disease and Prevention (CDC). This triggers an immune response by producing antibodies—and that protects you if you ever contract the real coronavirus.

The mRNA vaccines don’t contain live virus and will not give you COVID-19, the CDC says. They also don’t affect your DNA, since the mRNA doesn’t enter a cell’s nucleus, where genetic material is housed, and cells break down and discard the mRNA after making the protein.

The Pfizer and Moderna vaccines are safe, and both are about 95% effective.

You need two Pfizer and Moderna shots

The Pfizer-BioNTech and Moderna vaccines also both require two doses. “Both of these vaccines require a booster shot three to four weeks later, and thus it is imperative to know which vaccine you received so you receive the correct booster shot,” says Dr. Kevin Farmer, MD, adviser to PTPioneer.

Pfizer-BioNTech shots are given 21 days apart, and Moderna’s are given 28 days apart. And, you really need both to get the full immunity boost, Dr. Fagbuyi explains. Just getting one dose only offers partial immunity.

“If you get the second dose, you can get to about 95% efficacy,” Dr. Fagbuyi says. “It’s important to get that [second one], so you can have that full protection, not half protection.”

Related: People Are Getting Vaccinated Every Day, So How Much Longer Will We Have to Wear Masks?

But, there are some differences between the Pfizer and Moderna vaccines

One difference between the two approved vaccines is how they need to be shipped and stored. The Pfizer-BioNTech vaccine needs to be kept at super-cold temperatures of -70 degrees Celsius, or -94 degrees Fahrenheit, including during shipping. It can be thawed at room temperature or in a refrigerator, and must be used within two hours of thawing. The Moderna vaccine must be stored at -2 degrees Celsius (28.4 degrees Fahrenheit), which is similar to a regular freezer, and it must be used within 12 hours once it reaches room temperature.

Before it can be injected, the Pfizer-BioNTech vaccine is diluted with saline once it thaws out, while the Moderna doesn’t need to be diluted.

Another thing to note: The FDA approved the Pfizer-BioNTech vaccine for individuals 16 and older. Moderna’s has been approved for patients 18 and older.

What you should know about the AstraZeneca vaccine

A vaccine developed by the University of Oxford and pharmaceutical company AstraZeneca was recently approved by the U.K., but it hasn’t been given the go-ahead in the U.S. yet. It is expected to receive approval soon, though.

This vaccine was created using an “old school” method, Dr. Fagbuyi says. It uses the coronavirus’ genetic instructions to build a spike protein, which is stored via double-stranded DNA, according to The New York Times. The coronavirus spike protein’s gene is added to an adenovirus vector, a different kind of virus, which once injected, directs cells to make a protein that’s unique to COVID-19. The body then makes copies of the protein and uses the information later to fight the coronavirus if it’s ever infected.

“This type of vaccine has been around for a long time, and has had success with other illnesses,” Dr. Farmer explains. “This vaccine will also likely require a booster shot as well.”

The Oxford-AstraZeneca vaccine is believed to be around 90% effective, but there has been some uncertainty around its results.

Will you know which vaccine you’re getting?

“You’re well within your right to know which vaccine you’re taking,” Dr. Fagbuyi says.

When you get vaccinated, the CDC says you should receive a card or printout telling you which COVID-19 vaccine you received, the date and where you received it. You’ll also get a fact sheet listing the vaccine’s risks and benefits.

This information is especially important so you’ll know when to get the second shot, Farmer adds.

There may be some side effects, but that doesn’t mean vaccines aren’t safe

Similar side effects have been reported for all the vaccines, including pain and swelling at the injection site, according to the CDC. Fever, chills, headache, tiredness and flu-like symptoms may also occur, but will likely go away in a few days. In most cases, side effects have been mild.

But, these “expected responses” actually mean the vaccine is working, Dr. Fagbuyi explains, “Your body is doing what it’s supposed to do. It’s supposed to rev up and get ready to fight.”

Side effects shouldn’t keep you from getting vaccinated, Dr. Farmer says, since the only way to get the pandemic under control is by increasing the number of people with COVID-19 immunity. “We should all consider the vaccine, not only for our own health, but for the health of all of humanity,” he adds.

When your time comes to roll up your sleeve and get the shot, Dr. Fagbuyi suggests talking to your doctor about any concerns you have. “Then you have all the information and are well-informed on why you’re taking the vaccine and the myths can be demystified,” he adds. “Understand we are all in this together, and we’ve all got to get through this. Everybody has to play their part in this for us all to move forward to the new normal.”

Next, read up on everything you need to know about getting a COVID-19 vaccine.