From booster shots to FDA approval and emergency use authorization to efficacy against the delta variant and more, how do the COVID vaccines compare to each other and which is best for you?
There are various reasons why someone might choose a particular vaccine, but according to medical experts, the most important thing is getting vaccinated.
Still, it's a question many ask as they prepare for their vaccination.
According to medical experts, the three vaccines currently available in the U.S. each offer protection, but certain factors could determine which vaccine you are eligible to receive.
Here's a breakdown of what we know so far about each vaccine:
Are the COVID vaccines FDA approved?
The Food and Drug Administration last month granted Pfizer and BioNTech full U.S. approval of their COVID-19 vaccine – becoming the first in the U.S. to win the coveted designation.
Up until then, Pfizer's mRNA vaccine was on the U.S. market under an Emergency Use Authorization, which was granted by the FDA in December.
The vaccine is also still available under emergency use authorization (EUA) for younger people ages 12 through 15 and for a third booster dose in those with compromised immune systems, the FDA said.
Pfizer announced Monday its COVID-19 vaccine works for children ages 5 to 11 and that it will seek U.S. authorization for this age group soon -- a key step toward beginning vaccinations for youngsters.
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Emergency use authorization allows a vaccine to become available prior to full approval in the case of public health emergencies. The FDA can revoke the EUA at any time.
While Pfizer is currently the only vaccine to be fully approved, it is also the only vaccine authorized for emergency use in adolescents between the ages of 12 and 17, though Moderna filed for such approval earlier this year.
Moderna's two-shot and Johnson & Johnson's single-shot vaccines continue to be available under an emergency use authorization as well.
Moderna also announced in June that it had begun a “rolling submission” to the FDA of data from its studies of the two-dose mRNA vaccine.
“We are pleased to announce this important step in the U.S. regulatory process for a Biologics License Application (BLA) of our COVID-19 vaccine,” Moderna CEO Stephane Bancel said in a press release at the time. “We look forward to working with the FDA and will continue to submit data from our Phase 3 study and complete the rolling submission.”
Large-scale studies of the shots continued after Moderna’s emergency authorization. The FDA will scrutinize the information to see if the vaccine meets stringent criteria for full licensure.
Does age matter for vaccinations?
Pfizer's vaccine is currently the only vaccine authorized for emergency use in children as young as 12. Both Moderna and J&J's vaccines can only be used on people 18 and older.
However, Pfizer announced Monday it plans to seek U.S. authorization for children ages 5 to 11, saying its COVID-19 vaccine works for that age group.
For elementary school-aged kids, Pfizer tested a much lower dose -- a third of the amount that’s in each shot given now. Yet after their second dose, children ages 5 to 11 developed coronavirus-fighting antibody levels just as strong as teenagers and young adults, Dr. Bill Gruber, a Pfizer senior vice president, told The Associated Press.
The kid dosage also proved safe, with similar or fewer temporary side effects -- such as sore arms, fever or achiness -- that teens experience, he said.
Gruber said the companies aim to apply to the Food and Drug Administration by the end of the month for emergency use in this age group, followed shortly afterward with applications to European and British regulators.
Earlier this month, FDA chief Dr. Peter Marks told the AP that once Pfizer turns over its study results, his agency would evaluate the data “hopefully in a matter of weeks” to decide if the shots are safe and effective enough for younger kids.
Moderna also is studying its shots in elementary school-aged children. Pfizer and Moderna are studying even younger tots as well, down to 6-month-olds. Results are expected later in the year.
Age could also be a factor in determining who is eligible for booster shots of the Pfizer vaccine.
An FDA panel of outside experts overwhelmingly rejected a plan Friday to give Pfizer COVID-19 booster shots across the board, but instead agreed to distribute extra doses to people 65 and up as well as those at high risk of severe illness.
How effective are the COVID vaccines?
Vaccine efficacy has been a main question as the delta variant continues to spread around the country.
Health experts have said that a majority of hospitalizations and deaths associated with the variant in recent months are almost entirely in unvaccinated individuals. The CDC has said the risk of infection is 8x higher in the unvaccinated than the vaccinated, and the risk of hospitalization or death is 25x higher.
But is one better than the other at protecting against breakthrough infections in vaccinated populations?
Researchers in Belgium directly compared the Pfizer and Moderna COVID-19 vaccines by testing the antibodies of 2,500 health care workers after two doses of both vaccines.
The study found the Moderna vaccine produced more than double the antibodies compared to Pfizer, but doctors urge caution.
“Antibody level itself is interesting, but it doesn’t necessarily lead to a significant difference in the way the vaccine is performing,” said Dr. Allison Arwady, Commissioner of the Chicago Department of Public Health.
Another study to consider when comparing vaccines is one from the Mayo Clinic earlier this month, which is awaiting a full review.
That study found the risk of suffering a breakthrough COVID-19 infection with the delta variant after being fully vaccinated with the Moderna vaccine may be much lower than the risk for those who received the Pfizer vaccine.
The study reported that in July in Florida, where COVID cases are at an all-time high and the delta variant is prevalent, the risk of a breakthrough case was 60% lower for Moderna recipients as compared to Pfizer recipients.
Similarly, in Minnesota last month, the authors found that the Moderna vaccine (also known as mRNA-1273) was 76% effective at preventing infection, but the Pfizer vaccine (known as BNT162b2) was 42% effective.
The authors of the study found that both vaccines "strongly protect" against severe disease; the difference appears to be more about whether people get infected at all in the first place. The so-called pre-print study, which has not gone through a peer review or been published in an academic journal, was first released earlier this month.
Chicago is tracking breakthrough infections - COVID case reported in fully vaccinated individuals - by vaccine, but Arwady said they haven’t found a substantial pattern.
“We have seen the highest number of breakthrough infections in Chicagoans who have gotten Pfizer, but that is because the highest number of Chicagoans have gotten Pfizer, not that we’ve seen a major difference in someone who’s gotten Pfizer versus Moderna,” Arwady said.
When NBC 5 asked the Illinois Department of Public Health for a breakthrough breakdown, spokesperson Melaney Arnold said that “all three vaccines have been reported in breakthrough hospitalizations and deaths. Similar to the CDC, IDPH is not currently reporting that breakdown.”
While Moderna's two-dose vaccine remains "durable" six months after the second shot, immunity against the coronavirus will continue to wane and eventually diminish vaccine efficacy, the company said in slides that accompanied its second-quarter earnings report.
The company said its vaccine is 93% effective six months after the second dose. By comparison, Pfizer and BioNTech said their vaccine efficacy declined to around 84% after six months.
Johnson & Johnson reported last month that data showed their vaccine "generated strong, persistent activity against the rapidly spreading delta variant and other highly prevalent SARS-CoV-2 viral variants."
"Current data for the eight months studied so far show that the single-shot Johnson & Johnson COVID-19 vaccine generates a strong neutralizing antibody response that does not wane; rather, we observe an improvement over time," Dr. Mathai Mammen global head of Janssen Research & Development for Johnson & Johnson, said in a statement. "In addition, we observe a persistent and particularly robust, durable cellular immune response."
Delta, the dominant form of the disease in the U.S., is more transmissible than the common cold, the 1918 Spanish flu, smallpox, Ebola, MERS and SARS, according to the Centers for Disease Control and Prevention.
Will a booster shot be needed?
The U.S. has already approved Pfizer and Moderna boosters for certain people with weakened immune systems, such as cancer patients and transplant recipients.
But an FDA panel of outside experts on Friday voted not to endorse booster shots of the Pfizer COVID-19 vaccine across the board. Instead, the panel agreed to approve the distribution of extra doses to people 65 and up as well as those at high risk of severe illness.
The twin votes represented a heavy blow to the Biden administration’s sweeping effort, announced a month ago, to shore up nearly all Americans’ protection amid the spread of the highly contagious delta variant.
Members voted against that recommendation to give a third shot of Pfizer's vaccine to individuals age 16 and up, citing concerns about the level of evidence showing the boosters are safe for younger people.
“We’re being asked to approve this as a three-dose vaccine for people 16 years of age and older, without any clear evidence if the third dose for a younger person when compared to an elderly person is of value,” said committee member Dr. Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia.
Members cited a lack of safety data on extra doses and also raised doubts about the value of mass boosters, rather than ones targeted to specific groups.
“I don’t think a booster dose is going to significantly contribute to controlling the pandemic,” said Dr. Cody Meissner of Tufts University. “And I think it’s important that the main message we transmit is that we’ve got to get everyone two doses.”
While research suggests immunity levels in those who have been vaccinated wane over time and boosters can reverse that, the Pfizer vaccine is still highly protective against severe illness and death, even amid the delta variant.
Dr. Amanda Cohn of the CDC said: “At this moment it is clear that the unvaccinated are driving transmission in the United States.”
In a statement, Kathrin U. Jansen, Pfizer head of vaccine research and development, said the company continues to believe that boosters will be a “critical tool in the ongoing effort to control the spread of this virus.”
The FDA and CDC will most likely decide at some later point whether people who received the Moderna or J&J shots should get boosters.
Biden’s top health advisers, including the heads of the FDA and CDC, first announced plans for widespread booster shots in mid-August, setting the week of Sept. 20 as an all-but-certain start date. But that was before FDA staff scientists had completed their own assessments of the data.
How are the vaccines different?
Arguably one of the biggest difference between the three vaccines is the number of doses needed. The Johnson & Johnson vaccine requires just one dose, while both Pfizer's and Moderna's vaccines are two shots.
The Pfizer-BioNTech and Moderna vaccines also differ from traditional vaccines in their use of mRNA. Instead of introducing a weakened or an inactivated germ into your body, this vaccine injects mRNA, the genetic material that our cells read to make proteins, into your upper arm muscle. It teaches your body how to make the protein that triggers antibody production so if the real virus later enters your body, your immune system will recognize it, according to the federal Centers for Disease Control and Prevention.
Unlike the Pfizer and Moderna shots, the J&J vaccine uses a cold virus, called an adenovirus, to carry the spike gene into the body. J&J uses a human adenovirus to create its vaccine while a similar vaccine not yet approved in the U.S., AstraZeneca, uses a chimpanzee version.
J&J’s shot uses a cold virus like a Trojan horse to carry the spike gene into the body, where cells make harmless copies of the protein to prime the immune system in case the real virus comes along. It’s the same technology the company used in making an Ebola vaccine.
What are the side effects for each vaccine?
According to Pfizer, about 3.8% of their clinical trial participants experienced fatigue as a side effect and 2% got a headache. The side effects remain similar among young adults and adolescents.
Younger teens receive the same vaccine dosage as adults and have reported the same side effects, mostly sore arms and flu-like fever, chills or aches that signal a revved-up immune system, particularly after the second dose. However, the CDC is also looking into rare reports of mild myocarditis in some younger recipients, though it remains unclear if the condition is in fact linked to the vaccine.
Moderna says 9.7% of their participants felt fatigued and 4.5% got a headache.
Like Pfizer and Moderna's COVID-19 vaccines, the main side effects of the J&J shot are pain at the injection site and flu-like fever, fatigue and headache. These side effects usually start within a day or two of getting the vaccine, according to the CDC.
But the Johnson & Johnson vaccine was previously paused by U.S. regulators as they investigated reports of potentially dangerous blood clots known as cerebral venous sinus thrombosis, or CVST, in a small number of recipients.
The CDC and FDA said in April they were investigating unusual clots in six women that occurred 6 to 13 days after vaccination. All six cases were in women between the ages of 18 and 48. At the time, more than 6.8 million doses of the J&J vaccine had been administered in the U.S., the vast majority with no or mild side effects.
Ten days later, the agencies recommended resuming use of the vaccine, stating the benefits of the inoculations outweighed their risks.
The CDC's advisory panel didn't recommend restricting use of the vaccine to a particular age or gender, but did propose the possibility of adding a warning label for women under the age of 50.
There have also been reported cases of a rare, but serious, neurological disorder following Johnson & Johnson COVID-19 vaccinations, but preliminary data suggests the benefits of the shots still outweigh the risks, the Centers for Disease Control and Prevention said last month.
As of late last month, there were 8.1 cases of Guillain-Barre syndrome per 1 million doses, which is higher than expected in the general population and close to eight times the rate seen in Pfizer's and Moderna's shots, according to slides published ahead of a presentation before the CDC's Advisory Committee on Immunization Practices. Guillain-Barre is a rare neurological disorder in which the body's immune system mistakenly attacks part of the nervous system.
The data doesn't show a similar pattern with Pfizer's or Moderna's vaccines, the U.S. agency said. By comparison, there has been roughly one case of Guillain-Barre per million doses for people who received either of the two-dose mRNA vaccines, according to the agency.
Rare side effects, which scientists say are common, have also been detected in Pfizer's and Moderna's vaccines.
In late June, the FDA added a warning to patient and provider fact sheets for the mRNA vaccines to indicate a rare risk of heart inflammation. Both vaccines now include a warning about myocarditis and pericarditis after the second dose. Myocarditis is the inflammation of the heart muscle and pericarditis is the inflammation of the tissue surrounding the heart. Health officials said the benefits of receiving the vaccines still outweigh any risk.
The CDC reports the most common side effects for all three authorized vaccines is at the injection site. They include:
- Pain
- Redness
- Swelling
Common side effects in the body include:
- Tiredness
- Headache
- Muscle pain
- Chills
- Fever
- Nausea
"The Pfizer-BioNTech COVID-19 Vaccine and Moderna COVID-19 Vaccine both need 2 shots in order to get the most protection," the CDC states. "You should get the second shot even if you have side effects after the first shot, unless a vaccination provider or your doctor tells you not to get it."
The Centers for Disease Control and Prevention advises people to stick around for 15 minutes after vaccination, and those with a history of other allergies for 30 minutes, so they can be monitored and treated immediately if they have a reaction.
Are side effects more likely after the first or second dose?
With the two-shot vaccines, people are more likely to report side effects after their second dose, experts have said.
According to the CDC, side effects after your second shot "may be more intense than the ones you experienced after your first shot."
"These side effects are normal signs that your body is building protection and should go away within a few days," the CDC states.
In trials of both the Moderna and Pfizer vaccines, more people experienced side effects after the second dose.
But that doesn't mean that you shouldn't get your second shot if you get side effects after your first, experts say.
“When people receive that second dose, they are receiving the second booster to try and reach the maximum efficacy," said Dr. Edward Cachay, infectious disease specialist at UCSD.
The CDC also noted that both shots are needed.
"The Pfizer-BioNTech COVID-19 Vaccine and Moderna COVID-19 Vaccine both need 2 shots in order to get the most protection," the CDC states. "You should get the second shot even if you have side effects after the first shot, unless a vaccination provider or your doctor tells you not to get it."
What about side effects with booster shots?
The CDC stated that side effects with the third shot "were similar to that of the two-dose series."
The most common symptoms include fatigue and pain at the injection site, but "most symptoms were mild to moderate."
As with previous doses of the vaccine, the CDC notes that, "serious side effects are rare, but may occur."
