COVID-19 is the illness that’s caused by the novel coronavirus SARS-CoV-2. To date, the Food and Drug Administration (FDA) has provided emergency use authorization to three different vaccines to help protect against COVID-19:
Read on to learn how each vaccine works, how safe and effective each one is, and how to decide which one may be the right choice for you.
The vaccines that have been authorized for emergency use in the United States so far use two different types of technology:
Let’s break down how each vaccine uses one of these two technologies to help promote immunity against the coronavirus. Check out the infographic below to see a visual representation of how the mRNA and adenovirus vector vaccines work.
The Pfizer-BioNTech vaccine is also called BNT162b2 in the scientific literature and Comirnaty in some countries. It’s given in two doses spaced 21 days (3 weeks) apart.
The Pfizer-BioNTech vaccine uses mRNA technology, which develops immunity using the following process:
- When the vaccine is injected, surrounding cells take up the mRNA contained in the vaccine. Once inside a cell, mRNA stays outside the nucleus of the cell. It cannot interact with the DNA contained in the nucleus.
- MRNA provides instructions to the cell for making the spike protein that’s found on the surface of the coronavirus. Typically, the coronavirus uses the spike protein to bind to other cells and enter them.
- The cell uses the information provided by the mRNA to produce the spike protein. When this process is complete, the mRNA is destroyed.
- The cell then displays the spike protein on its surface. Immune cells in your body recognize the spike protein as a foreign substance and start building an immune response to it.
- New antibodies and immune cells that recognize this specific spike protein are produced as your body develops your immune response.
- Your body has now built an immune response to the specific spike protein on the surface of the coronavirus. Your immune system can now help protect you from getting sick with COVID-19 because it’s been “trained” to fight against infections caused by exposure to this coronavirus in the future.
The Pfizer-BioNTech vaccine must be stored at ultra-cold temperatures between -112°F (-80°C) and -76°F (-60°C) to keep the mRNA molecule in the vaccine stable.
Once diluted and prepared for an injection, it can remain at room temperature for
You may see the Moderna vaccine called mRNA-1273 in scientific papers. Like the Pfizer-BioNTech vaccine, the Moderna vaccine is given in two doses spaced 28 days (4 weeks) apart.
The Moderna vaccine also uses mRNA technology that uses the same mechanism as the Pfizer-BioNTech vaccine to build immunity to the coronavirus spike protein.
Similar to the Pfizer-BioNTech vaccine, the Moderna vaccine must also be stored at very cold temperatures, between -58°F (-50°C) and 5°F (-15°C). Once a vial is opened and prepared for an injection, it’s stable at room temperature for
Johnson & Johnson (J&J)
You may see the Johnson & Johnson (J&J) vaccine referred to as JNJ-78436735 or Ad26.COV2.S in scientific papers. Unlike the Pfizer-BioNTech and Moderna vaccines, the J&J vaccine can be given as a single dose.
The J&J vaccine uses an adenovirus vector, which is a modified inactivated adenovirus (a type of virus) that’s designed not to cause disease in people.
Once the vaccine delivers the adenovirus vector into a host cell, the vector is broken down and the adenovirus cannot cause any harm in the body.
Here’s how the J&J vaccine works:
- When the vaccine is injected, the adenovirus enters into the surrounding cells. Adenoviruses cannot integrate into your DNA. An adenovirus’s genetic material cannot change or interact with your DNA in any way.
- Your cells use the information from the adenovirus’s DNA to make spike protein.
- Once the spike protein is made, it’s displayed on the surface of the cell.
- Your immune system notices the spike protein on the surface of the cell and recognizes it as a foreign substance. It then produces an immune response to help fight against the protein.
- As in the mRNA vaccines, antibodies and immune cells that specifically recognize the spike protein are generated. This helps prevent you from becoming sick with COVID-19.
Unlike the two mRNA vaccines, the J&J vaccine can be refrigerated rather than frozen because it’s more stable at higher temperatures. Once a vial is opened and prepared for injection, it can be kept at room temperature for
Vaccine efficacy measures the percent reduction of COVID-19 in those who are vaccinated compared with those who have not been vaccinated.
Efficacy is one of the key metrics reported in clinical trials that the FDA reviews when deciding to grant emergency use authorization. Efficacy metrics are also more reliable when a higher number of participants are involved in a clinical trial or study.
Efficacy is measured in a trial or study about
This means you’re considered fully vaccinated when it’s been:
- 2 weeks after your second dose of the Pfizer-BioNTech or Moderna vaccine
- 2 weeks after receiving the single-dose J&J vaccine
Let’s take a look at efficacy data from the large-scale clinical trials for these vaccines.
In the phase 3 clinical trial of the Pfizer-BioNTech vaccine, 43,448 people participated. Each participant received two doses of the vaccine or two doses of a placebo spaced 21 days (3 weeks) apart.
Researchers assessed vaccine efficacy 7 days after the second dose of the vaccine. At this time, it was found that vaccine efficacy was 95 percent.
Here’s some other important data from the trial:
- COVID-19 after second dose. Only eight people in the vaccine group got COVID-19 at least 7 days after their second dose of the vaccine. In the placebo group, 162 people got COVID-19 in the 7 days after their second injection.
- COVID-19 between doses. Only 39 cases of COVID-19 were observed in the vaccine group between the first and second doses. This means the vaccine is 52 percent effective between the two doses. The placebo group had 82 cases of COVID-19 between the first and second injections.
- Severe COVID-19. There were 10 cases of severe COVID-19 after the first injection. Only one was in the vaccine group, while the other nine were reported in the placebo group.
- COVID-19 deaths. No deaths from COVID-19 were reported during the study.
In the phase 3 clinical trial of the Moderna vaccine, 30,420 people participated. In this trial, each participant got either two doses of the vaccine or two doses of a placebo spaced 28 days (4 weeks) apart.
Researchers evaluated vaccine efficacy 14 days after the second dose of the vaccine. At this point, vaccine efficacy was found to be 94.1 percent.
Here’s some other important data from the trial:
- COVID-19 after second dose. Only 11 people in the vaccine group got COVID-19 at least 14 days after their second dose. In the placebo group, 185 people got COVID-19 after their second injection.
- COVID-19 between doses. In the 14 days after the first dose, only 11 cases of COVID-19 were found in the vaccine group. This corresponds to 95.2 percent efficacy between doses. The placebo group reported 225 cases of COVID-19 between injections.
- Severe COVID-19. No severe cases of COVID-19 were reported in the vaccine group, while 30 cases were reported in the placebo group.
- COVID-19 deaths. Only one COVID-19 death was reported from the placebo group after the participant developed severe COVID-19.
Johnson & Johnson
In the phase 3 clinical trial of the J&J vaccine, 39,058 people participated. The trial tested a single dose of the vaccine.
Researchers evaluated vaccine efficacy 14 days after the single dose of the vaccine was given. The results also broke down efficacy by COVID-19 severity and location.
Overall, J&J vaccine efficacy was found to be 66.3 percent. Overall efficacy varied among countries:
- United States: 74.4 percent
- Brazil: 66.2 percent
- South Africa: 52 percent
J&J vaccine efficacy for severe to critical COVID-19 was:
- Overall: 76.3 percent
- United States: 78 percent
- Brazil: 81.9 percent
- South Africa: 73.1 percent
Here’s some other important data from the trial:
- COVID-19. In the vaccine group, 173 people became ill with moderate to critical COVID-19 at least 14 days after vaccination, compared with 509 people in the placebo group.
- Asymptomatic infection. A small group of participants received an antigen test 71 days after injection. This test detected asymptomatic coronavirus infection in 18 people in the vaccine group and 50 people in the placebo group. This means the vaccine is 65.5 percent effective against asymptomatic infection.
- Severe to critical COVID-19. Of the participants who developed COVID-19, 19 cases of severe to critical COVID-19 were reported in the vaccine group, while 80 were reported in the placebo group.
- Hospitalization. Thirty-one hospitalizations due to COVID-19 were reported in the 14 days after the injection. Only two were in the vaccine group, while 29 were in the placebo group.
- COVID-19 deaths. Five COVID-19-related deaths were reported. They were all from the placebo group.
COVID-19 vaccines must be proven effective and safe before the FDA can grant emergency use authorization.
The Pfizer-BioNTech, Moderna, and J&J COVID-19 vaccines have met
Is there anyone who shouldn’t be vaccinated?
People who have had severe allergic reactions to a COVID-19 vaccine or any of its ingredients should not be vaccinated.
Each vaccine manufacturer provides fact sheets with complete lists of vaccine ingredients:
What if I have an underlying health condition?
- a previous dose of the vaccine
- any vaccine ingredients
This includes people who have a weakened immune system. Specific safety data for people with compromised immune systems is limited. But since these authorized COVID-19 vaccines don’t contain live virus, they
Vaccination is important for people with underlying health conditions. This is because many types of underlying health conditions can increase the risk of severe COVID-19.
Before getting vaccinated, talk with a healthcare professional and let them know about any underlying health conditions you have or medications you’re taking.
What if I’m pregnant or breastfeeding?
Pregnant people are also at an increased risk of serious illness as well as preterm birth and other pregnancy outcomes due to COVID-19.
If you’re pregnant or breastfeeding and are concerned about COVID-19 vaccination, talk with a healthcare professional about:
- benefits and risks of getting vaccinated
- currently available safety data
- potential risks of contracting the coronavirus and developing COVID-19 while pregnant
Each COVID-19 vaccine is associated with side effects.
We don’t yet know whether there are long-term side effects to these vaccines. But the
You may experience one or more of the following
These side effects are typically mild to moderate and go away in a few days. Side effects felt throughout the body, like fever and aches and pains, are
More serious side effects include a serious allergic reaction called anaphylaxis, which can include symptoms like:
- trouble breathing
- swelling in the face and throat
- rapid heart rate
- feeling dizzy or weak
The Pfizer-BioNTech clinical trial reported only four other serious side effects from the vaccine:
- shoulder injury related to vaccine administration
- swelling of lymph nodes (lymphadenopathy)
- paresthesia in the right leg
- paroxysmal ventricular arrhythmia
Researchers also reported no deaths due to receiving either the vaccine or the placebo during the trial.
- pain, swelling, or redness at the injection site
- muscle or joint pain
- nausea or vomiting
These side effects are often mild to moderate and go away in a few days. Systemic side effects like fever and aches and pains are
The Moderna vaccine is also associated with delayed pain, swelling, or redness at the injection site, sometimes called “COVID arm.” The Moderna clinical trial data found that this typically happens 8 or more days after either dose and lasts for 4 to 5 days.
Anaphylaxis has also been reported as a serious side effect of the Moderna vaccine. Clinical trial data also notes that treatment-related severe side effects were higher in the vaccine group than the placebo group.
Seventy-one (0.5 percent) of the 15,185 participants who got the vaccine reported severe side effects, including:
In this clinical trial, two deaths occurred in the vaccine group. One died by suicide, while the other died from cardiac arrest. Investigators could not confirm whether these deaths were related to the vaccine.
Johnson & Johnson
- pain, swelling, or redness at the injection site
- muscle pain
Anaphylaxis has also been reported with the J&J vaccine.
The J&J vaccine is also associated with the risk of a very rare blood clot condition called thrombosis with thrombocytopenia syndrome (TTS). TTS was most often observed in females between the
Other severe side effects observed during the clinical trial of the J&J vaccine — only reported by 7 out of the 21,895 participants who received the vaccine, or about 0.03 percent — included:
While researchers did observe blood clot events, most were in people with underlying conditions that increase blood clot risk. In total, 11 clotting events were reported in the vaccine group compared with three in the placebo group.
Lastly, the clinical trial of the J&J vaccine reported three deaths in the vaccine group. However, researchers concluded that none of these deaths were related to the vaccine.
It’s completely normal for viruses to mutate. These mutations can sometimes harm the virus, making it weaker or less infectious. But new mutations can also provide a virus with an advantage.
So far, many virus variants have been detected for the coronavirus. Some are considered “variants of concern” because they may be associated with increased transmission or can break through the immune system, even in vaccinated people.
Some reported variants include:
- Alpha (B.1.1.7.). First detected in the United Kingdom, this variant is about
50 percentmore transmissible than the original coronavirus.
- Beta (B.1.351). This variant was first detected in South Africa. It’s also about
50 percentmore transmissible than the original variant. It also appears to be able to evade the immune system.
- Delta (B.1.617.2). This variant emerged during a surge of COVID-19 cases in India and has since spread worldwide. It is
nearly twiceas infectious as previous variants.
- Gamma (P.1). This variant was first identified in Brazil and Japan. Like Beta, it appears to be able to evade the immune system.
Research into how effective each vaccine is against coronavirus variants is ongoing. Let’s discuss what we know so far.
An April 2021 study assessed the Pfizer-BioNTech vaccine’s activity against variants by using serum from people who had been vaccinated with the Pfizer-BioNTech vaccine. Serum is the part of the blood that contains antibodies.
When this serum was tested against test viruses with spike proteins from different variants, researchers found that Alpha and Gamma test viruses were neutralized at a similar level to the original variant. Neutralization of Beta test viruses was still robust, but lower.
A July 2021 study from Qatar, where most cases of COVID-19 are due to Alpha or Beta, looked at vaccine efficacy in real-world circumstances. Researchers looked at confirmed COVID-19 cases in vaccinated and unvaccinated people.
The vaccine efficacy in people who had been fully vaccinated with the Pfizer-BioNTech vaccine was estimated to be:
- 89.5 percent for Alpha
- 75 percent for Beta
- 100 percent for severe, critical, or fatal disease caused by either variant
Additionally, research from public health officials in the United Kingdom indicates that the Pfizer-BioNTech vaccine is also effective against Alpha and Delta. The vaccine’s efficacy in fully vaccinated people was:
- 93 percent for Alpha
- 88 percent for Delta
A July 2021 study found that two doses of the Pfizer-BioNTech vaccine were about 88 percent effective against the Delta variant.
Similar serum studies have also been carried out for the Moderna vaccine.
One study observed that test viruses with spike protein from Alpha were neutralized similarly to the original coronavirus variant. But neutralization was about 6.4 times lower against test viruses with the Beta spike protein.
Another serum study from June 2021 looked at the Moderna vaccine’s effectiveness against Beta and B.1.429, a variant first detected in California.
Researchers found that the B.1.429 variant was two to three times less sensitive to neutralization, while Beta was 9 to 14 times less sensitive.
Johnson & Johnson
The clinical trial of the J&J vaccine was carried out at a different point during the pandemic than the trials for the Pfizer-BioNTech and Moderna vaccines. During the J&J trial, several variants were circulating or common in many parts of the world.
For example, researchers in the trial found that 95 percent of sequenced COVID-19 cases in South Africa were due to the Beta variant. The vaccine efficacy of the J&J vaccine in South Africa was 52 percent overall and 73.1 percent for severe to critical COVID-19.
In Brazil, 69 percent of the sequenced COVID-19 cases were caused by the P.2 lineage at the time of the trial. Here, the efficacy of the J&J vaccine was 66.2 percent overall and 81.9 percent for severe to critical COVID-19.
Overall, the J&J vaccine still appears to be quite effective at reducing the likelihood of developing COVID-19, particularly for severe to critical COVID-19, in locations with variants.
The U.S. federal government is providing all COVID-19 vaccines
If you seek a COVID-19 vaccination during this time, you cannot be charged for:
- the vaccine itself
- copays, coinsurance, or administration fees
- an office visit or other fee if the only service you received was a COVID-19 vaccination
It’s unclear whether any of these three authorized vaccines will still be free after the pandemic ends, since all three are produced by for-profit pharmaceutical companies.
But it’s likely (though not yet confirmed) that you’ll have to pay for the COVID-19 vaccine after the pandemic is declared over by the World Health Organization (WHO) or other national public health agencies. Potential payment may include both receiving the initial vaccination or a booster shot.
The Pfizer-BioNTech, Moderna, and J&J COVID-19 vaccines are currently authorized in the United States by the FDA under an emergency use authorization (EUA). This is a little bit different than a typical FDA approval.
Simply put, an EUA is a method through which the FDA can allow unapproved medical products to be used during a public health emergency, like a pandemic.
When reviewing a product for an EUA, the FDA must decide that the overall benefits of the product outweigh its potential risks.
Here’s what happens during this process:
- Submitting for EUA. A company needs to submit both safety and efficacy results from a phase 3 clinical trial to the FDA. It’s possible for this trial to still be in progress during submission as long as it meets certain milestones set by the FDA.
- Internal review. FDA scientists comb through the clinical trial data that the company has submitted.
- External advisory panel review. An external advisory panel of scientists and public health experts also goes over and discusses the data.
- A decision is made. The FDA considers the feedback from both the internal review and the external advisory panel review when deciding to grant EUA to a product.
In addition to the United States, these three COVID-19 vaccines have been authorized or approved in a variety of other countries around the world.
It’s important to note that additional authorizations or approvals may occur rapidly.
The Pfizer-BioNTech vaccine
On December 31, 2020, the
The Moderna vaccine
Additionally, on April 30, 2021, the
Johnson & Johnson
The J&J vaccine
It was listed by the
Now, let’s briefly discuss each company that produced the vaccine.
Pfizer and BioNTech
Pfizer is an American pharmaceutical company headquartered in New York City. Its mission is to develop drugs and vaccines that can help improve health and wellness.
Some of Pfizer’s more well-known products include:
- Enbrel (etanercept), which treats conditions like rheumatoid arthritis and psoriatic arthritis
- Lipitor (atorvastatin), which can help lower cholesterol
- Lyrica (pregabalin), which can treat nerve pain
- Prevnar 13, a pneumococcal vaccine
- Viagra (sildenafil), which can treat erectile dysfunction
Pfizer collaborated with the German biotechnology company BioNTech to produce the Pfizer-BioNTech vaccine. This collaboration emerged from an initial agreement in 2018 to develop an mRNA-based vaccine for influenza.
Moderna is an American pharmaceutical and biotechnology company headquartered in Cambridge, Massachusetts. Moderna is a much smaller company than Pfizer. But it has a relatively long history in researching mRNA vaccines, dating back to 2015.
Moderna has clear ambitions for developing mRNA technology for a variety of therapeutic uses, such as additional vaccines and cancer therapies.
The COVID-19 vaccine is currently Moderna’s only product on the market. It was developed in collaboration with researchers from the
Janssen/Johnson & Johnson
Janssen is a pharmaceutical company headquartered in Beerse, Belgium, and owned by the Johnson & Johnson corporation.
Janssen develops products in several main therapeutic areas, including infectious disease, oncology, and cardiovascular disease. Some of its more well-known products are:
- Imodium (loperamide), which treats diarrhea
- Lexapro (escitalopram), a selective serotonin reuptake inhibitor (SSRI) antidepressant
- Remicade (infliximab), which treats conditions like rheumatoid arthritis and psoriatic arthritis
- Risperdal (risperidone), which treats conditions like schizophrenia and bipolar disorder
- Stelara (ustekinumab), which treats psoriasis and Crohn’s disease
Janssen developed its COVID-19 vaccine for Johnson & Johnson. That’s why you may also see the J&J vaccine referred to as the Janssen vaccine.
At first glance, the efficacy of the J&J vaccine appears lower than that of the Pfizer-BioNTech and Moderna vaccines. But the J&J vaccine also appears to provide sufficient protection after just one dose instead of two.
In most cases, you have a choice as to the vaccine you get due to increased supply and access to these vaccines across the United States.
If you’re concerned about the risk of TTS associated with the J&J vaccine, you’ll likely be able to request the Pfizer-BioNTech or Moderna vaccine instead.
If you have a specific vaccine preference, use the VaccineFinder search tool to locate a COVID-19 vaccination site near you. This search tool lets you filter your results by vaccine type, so you can find the one that you’d like to receive.
Three different COVID-19 vaccines have been authorized for emergency use in the United States. All three have been proven to be safe and effective based on large-scale clinical trials. None of them are necessarily better than the others.
It’s ultimately your choice as to what vaccine you get. Getting vaccinated as soon as possible will help protect you and your loved ones from COVID-19. It will also help slow the spread of the coronavirus in your community.
Talk with a healthcare professional if you’re concerned about vaccine side effects or underlying health conditions that may be affected by the vaccines.