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Here's everything we know about the COVID-19 vaccine

There are still questions surrounding the coronavirus vaccine. Here's what we know and what we don't about the Pfizer, Moderna and Johnson & Johnson shots.

INDIANAPOLIS — As Indiana continues to make the COVID-19 vaccine available to more Hoosiers, there are still plenty of questions about the shots. We have answers to some of those questions, while others are still up in the air.

Pfizer-BioNTech vaccine

The Pfizer-BioNTech vaccine became the first COVID-19 vaccine to receive emergency use authorization (EUA) from the FDA on Dec. 11, 2020. Individuals 16 and older can receive the vaccine. The FDA authorized the vaccine after approximately 44,000 people participated in a study. Pfizer's trial included participants as young as 12, but the FDA only approved the vaccine for individuals at least 16 years old. After a median of two months of study participants receiving both doses of the vaccine, the FDA did not identify any safety concerns that should keep them from authorizing the vaccine.

Preliminary data from the CDC indicates the vaccine is 95 percent effective in preventing COVID-19 after two doses.

RELATED: In bid to end pandemic, FDA approves Pfizer COVID-19 vaccine for emergency use

How it works

The Pfizer-BioNTech vaccine uses messenger RNA (mRNA), which has been studied for more than a decade, according to the CDC. Vaccines that contain mRNA do not contain a live virus and do not affect a person's DNA. So how do they work?

"mRNA are basically the instructions that are packaged in this little lipid package injected into the vaccine, it gets into your cell then teaches your cell basically how to make the virus protein to mount an immune response," said Dr. James Cutrell, infectious disease specialist at UT Southwestern in Dallas.

mRNA vaccines can trigger an immune response in the body, but they cannot infect the vaccinated person with the disease itself.

The Pfizer-BioNTech vaccine requires two shots, at least 21 days apart.

Side effects

The FDA says most side effects to the vaccine are mild to moderate and should subside in a few days. These were the most commonly reported side effects recorded in the clinical studies:

  • Pain at injection site
  • Fatigue
  • Headache
  • Muscle pain
  • Chills
  • Joint pain
  • Fever
  • Injection site swelling
  • Injection site redness
  • Nausea
  • Malaise
  • Lymphadenopathy

Who should not get it

There are some people who should not get the vaccine, according to the CDC. Anyone who has previously experienced these should not get the vaccine:

  • Severe allergic reaction (e.g., anaphylaxis) after a previous dose of an mRNA COVID-19 vaccine or any of its components
  • Immediate allergic reaction of any severity to a previous dose of an mRNA COVID-19 vaccine or any of its components (including polyethylene glycol [PEG])
  • Immediate allergic reaction of any severity to polysorbate (due to potential cross-reactive hypersensitivity with the vaccine ingredient PEG)

People who are sick with symptomatic COVID-19 should also avoid the vaccine. The CDC says patients should be completely recovered and out of isolation before getting vaccinated.

Moderna vaccine

The FDA issued EUA for Moderna's COVID-19 vaccine on Dec. 18, 2020. Individuals 18 and older can receive the vaccine. The FDA authorized the vaccine after approximately 30,000 people participated in phase 3 of a study. Moderna's study only included participants who were at least 18 years old. After a median of seven weeks of study participants receiving the two doses of the vaccine, the FDA did not identify any safety concerns that should keep them from authorizing the vaccine. The FDA again reviewed safety data after a median of nine weeks after participants received two doses of the vaccine.

Preliminary data from the CDC indicates the Moderna vaccine is 94.1 percent effective in preventing COVID-19 after two doses.

RELATED: FDA gives green light to Moderna COVID-19 vaccine, 2nd shot in US arsenal

How it works

Like the Pfizer vaccine, the Moderna vaccine uses mRNA to get the body to produce antibodies so it's prepared to fight against a future infection. It does not carry a live virus; there is no risk of the vaccine infecting you with COVID-19; and it will not change your DNA.

The Moderna vaccine requires two shots, at least 28 days apart.

Side effects

The FDA says most side effects to the vaccine are mild to moderate and should subside in a few days. These were the most commonly reported side effects recorded in the clinical studies:

  • Pain at injection site
  • Fatigue
  • Headache
  • Muscle pain
  • Joint pain
  • Chills
  • Nausea/vomiting
  • Axillary swelling and tenderness of the vaccination arm
  • Fever
  • Injection site swelling
  • Injection site redness

Who should not get it

Like the Pfizer vaccine, who should not get the Moderna vaccine boils down to allergies. The CDC recommends most people get the vaccine unless they fall into one of these categories:

  • Severe allergic reaction (e.g., anaphylaxis) after a previous dose of an mRNA COVID-19 vaccine or any of its components
  • Immediate allergic reaction of any severity to a previous dose of an mRNA COVID-19 vaccine or any of its components (including polyethylene glycol [PEG])
  • Immediate allergic reaction of any severity to polysorbate (due to potential cross-reactive hypersensitivity with the vaccine ingredient PEG)

People who are sick with symptomatic COVID-19 should also avoid the vaccine. The CDC says patients should be completely recovered and out of isolation before getting vaccinated.

RELATED: VERIFY: Who should NOT get vaccinated for COVID-19?

Johnson & Johnson vaccine

The FDA issued EUA for the COVID-19 vaccine from Janssen Pharmaceuticals — which is owned by Johnson & Johnson — on Feb. 18, 2021. It was authorized for use on individuals 18 and older. The FDA gave EUA after nearly 44,000 people participated in a phase 3 trial. Janssen's study only included participants who were at least 18 years old. After a median of eight weeks of study participants receiving either the vaccine or a placebo, the FDA did not identify any safety concerns that should keep them from authorizing the vaccine.

Preliminary data from the CDC indicates the Johnson & Johnson vaccine is around 66 percent effective against moderate to severe COVID-19 cases after a single dose.

RELATED: Why doctors aren't focused on Johnson & Johnson's lower vaccine efficacy

How it works

The Johnson & Johnson vaccine is a viral vector vaccine, which uses a modified version of a different virus — the vector — to deliver instructions to our cells, according to the CDC. Scientists began creating these types of vaccines in the 1970s, and viral vectors have recently been used in vaccines against Ebola and the Zika virus. The Johnson & Johson vaccine cannot infect someone with COVID-19 or the virus used as the vector. So how does it work?

According to the CDC, the vector (a harmless virus) will enter a cell in the body and then use the its machinery to produce a harmless piece of the virus that causes COVID-19, known as a spike protein. That spike protein is only found on the surface of the virus that causes COVID-19. The cell the vector entered will then display the spike protein, causing the bodies to produce antibodies that fight off the infection.

Unlike the Pfizer and Moderna vaccines, the Johnson & Johnson vaccine only requires one dose.

Viral vector vaccines do not affect or interact with a person's DNA.

Side effects

The most commonly reported side effects from study participants were pain at the injection site, headache, fatigue, muscle aches and nausea, according to the FDA. Most of those were mild to moderate and only lasted one to two days. Both Janssen and vaccine providers are required to report more severe side effects to the CDC's Vaccine Adverse Event Reporting System.

How the vaccines differ

The Pfizer and Moderna vaccines are both pretty similar when it comes to efficacy and the science behind them. The biggest difference between the two is how they must be stored.

The Moderna vaccine must be stored at -4 degrees Fahrenheit — about as cold as an average freezer. The Pfizer vaccine, on the other hand, must be stored in extreme cold temperatures — about -94 degrees Fahrenheit, which is colder than Antarctica's winter.

The Johnson & Johnson vaccine differs from the other two in both how it's made and how it's stored. It uses a viral vector, as opposed to mRNA injected directly into cells, to trigger an immune response. 

The Johnson & Johnson vaccine can be stored at normal refrigeration temperatures — between 35 and 46 degrees Fahrenheit. That makes it a lot easier and cheaper to transport to more places.

RELATED: VERIFY: Explaining how the Johnson & Johnson vaccine works and what makes it different from others

Lastly, the Johnson & Johnson vaccine requires only one shot, while the others require two.

How/why were the vaccines approved so quickly?

None of the vaccines shortcut FDA safety measures to get them out more quickly. In fact, Dr. David Diemert, who helped develop the Moderna vaccine, said it was the opposite.

"We’re probably doing more in terms of safety assessments for this trial, because of the speed we want to be able to get an answer," Diemert said during development. "It's been exhausting but rewarding at the same time."

All data is tracked by the Data and Safety Monitoring Board, an independent group of 10 to 15 experts that oversee all vaccine trials and have the power to pause or stop them over safety concerns.

While COVID-19 itself is a new, novel disease, scientists have seen other similar diseases in the past — like SARS in 2002 and MERS in 2012 — that gave them a head start in figuring out what would and wouldn't work.

That said, because the vaccine developers were only looking for an EUA from the FDA, the agency only requires two months of data for half of trial patients — a much shorter time period than trials seeking licensure.

Furthermore, many typical barriers were removed from the entire process — including funding challenges and finding participants — thanks to a worldwide push to quickly develop a vaccine.

There is an inherent risk with not being able to track data for rare side effects that may not show up in patients until months later, but experts have said it's most likely worth the risk.

What we don't know

Despite the extensive information about the vaccines, there are still things we don't have answers to yet. Because data has not yet been tracked for long-term effects of the vaccines, it's impossible to know what — if any at all — symptoms or side effects vaccinated individuals may experience long-term.

Long-term effectiveness is also unknown. There is a chance additional COVID-19 booster shots will be necessary annually, like the flu shot.

Effectiveness in some populations, including young children, pregnant women, and individuals with weakened immune systems were not included in the studies, so there are still questions with those groups. The FDA only approved the Pfizer vaccine for people 16 and older, while the Moderna and Janssen vaccines are for people 18 and older. Pregnant women, immunocompromised individuals, or people with underlying health conditions should check with a health care provider before receiving the vaccine.

That said, the CDC says there's not evidence to suggest any of the vaccines could put pregnant women at risk of any complications. There is also no evidence that fertility problems are a side effect of the vaccines.

Lastly, more research is needed to determine if the current vaccines will be effective against new variant strains recently found in the U.S. and overseas. Developers believe they will be effective against slight mutations, but researchers will continue to do tests to monitor.

RELATED: Will COVID-19 vaccines work on the new coronavirus variant?