Children's Hospital Colorado

COVID-19 Vaccine Approvals: What Comes Next

Patient giving thumbs up after getting vaccine.

This page was updated Sept. 28, 2021. Due to the evolving nature of the pandemic, recommendations can change quickly. Please follow all health and safety guidelines set by your local public health authorities. Reference the Centers for Disease Control and Prevention (CDC) and Colorado Department of Public Health and Environment (CDPHE) for ongoing updates on COVID-19.

When will the COVID-19 vaccines be available for younger children? How do we know the vaccines are safe? Our pediatric experts, infectious disease specialists Sean O’Leary, MD, MPH, and Samuel Dominguez, MD, PhD, and Chief Medical Officer David Brumbaugh, MD, break down the latest on the effort to produce safe and effective vaccines against COVID-19.

Another milestone: full FDA approval of Pfizer-BioNTech COVID-19 vaccine

On August 23, the U.S. Food and Drug Administration announced its formal approval of the Pfizer-BioNTech COVID-19 vaccine for people ages 16 and older. Known as Pfizer’s COVID-19 vaccine, it will now be marketed as Comirnaty (koe-mir’-na-tee), for the prevention of COVID-19 in people 16 and up. The vaccine continues to be available under emergency use authorization (EUA) for other groups, including for young people 12 to 15. For some individuals who have conditions that affect their ability to fight off infection (those who are immunocompromised), a third dose of the Pfizer vaccine is now available, also under EUA.

What does full FDA approval mean?

The vaccine met the FDA’s rigorous scientific standards for the emergency use authorization back in December 2020 and was expanded in May to include adolescents and teens 12 and older. To earn full FDA approval, Pfizer had to meet an even more stringent and extensive set of standards for safety, effectiveness and manufacturing quality.

“This approval is momentous because it confirms, through very strict and thorough data collection, that the vaccine is safe and effective,” says Dr. Brumbaugh. “Of course, millions of Americans have already received the vaccine under the emergency use authorization and it has saved countless lives — and now, millions more should feel comfortable receiving the vaccine because it has been further vetted in this even more comprehensive way.”

This confirmation of the vaccine’s safety and effectiveness is important because it will likely instill confidence in people who have been hesitant to be vaccinated. The more people who are vaccinated, the fewer hospitalizations and deaths we’ll see and the less opportunity the virus will have to infect people and mutate into new variants that could make the vaccines less effective at preventing severe disease. That all plays a huge role in protecting children under 12 who aren’t yet eligible for the vaccines. Until young children are also eligible, surrounding them with vaccinated adolescents, teens and adults is one of the most powerful ways to keep them protected from the virus.

“This approval should provide further peace of mind that many people need to get the vaccine, which will make our children safer and take us one step closer to ending the pandemic,” says Dr. Brumbaugh.

For more information on the processes and standards involved in full FDA approval and how Pfizer fulfilled the requirements, read the agency’s update.

Safe and effective vaccine available for kids 12+

On May 10, the FDA expanded its emergency authorization of the Pfizer-BioNTech vaccine to include adolescents ages 12 to 15. (Previously, the vaccine had only been authorized for people 16 and older.) This eagerly anticipated development marked another key milestone in the pandemic, allowing many more children the chance to be protected from the coronavirus and its emerging variants.

Pfizer’s vaccine trials in children ages 12 to 15 found the vaccine to be 100% effective in preventing COVID-19 among trial participants and with no sign of safety concerns. “The evidence is clear,” says Dr. O’Leary. “Not only is the Pfizer vaccine incredibly effective in kids ages 12 and older, it’s incredibly safe.”

Read our leaders’ take on the news and why we’re encouraging parents to get their children vaccinated as soon as possible. Or, learn how to sign up to get vaccinated here at Children’s Colorado.

According to the Centers for Disease Control and Prevention, more than 5 million adolescents have now received at least one dose of the vaccine. Early data from Moderna’s clinical trials in kids ages 12 to 17 have shown promising results, which means Moderna’s mRNA vaccine may also be authorized for use in everyone ages 12 and older soon.

When can I get a COVID-19 vaccine?

Everyone over the age of 12 is now eligible to receive the COVID-19 vaccine in the U.S. State and federal agencies are working as quickly as possible to safely deliver vaccines to anyone who wants one, and the pace so far has been impressive – more than half of all U.S. adults are now fully vaccinated. That’s zero to 50% in less than six months.

As more contagious variants of the coronavirus spread, including the delta variant, it’s even more urgent that everyone who can get vaccinated do so.

When will younger kids be vaccinated?

The emergency use authorization for Pfizer’s vaccine in kids 12 and older represents good progress. But kids younger than 12 still need to wait.

Children younger than 12 are not likely to get the vaccine for weeks or months. Medical experts are projecting that the earliest younger kids will become eligible is sometime in the fall or winter of 2021, though it’s difficult to predict. On September 28, Pfizer-BioNTech announced they had submitted initial data from their clinical trials in the 5- to 11-year-old cohort to the FDA. Their formal request for emergency use authorization will follow in the “coming weeks.” 

While an expansion of the EUA for younger children was initially expected as early as September, the timeline lengthened when the government requested that Pfizer enroll more children in clinical trials to investigate potential side effects in more depth.

“The challenge is in being able to vaccinate children as soon as possible to protect them while ensuring we have a large enough sample to find and investigate any potential side effects, says Dr. Brumbaugh. “With the rapid spread of the delta variant, some pediatric experts are calling on the FDA to expedite their review. Ultimately, we’re hoping that we have a safe, effective vaccine approved for 5- to 11-year-olds by the end of the year, but we’re encouraging parents to remain patient while the vaccine is thoroughly investigated.”

Why it’s taking longer for kids

It’s important that COVID vaccines are studied in kids before using them widely. There are good reasons for studying kids separately from adults and for studying kids after adults.

One is that kids are at far lower risk for serious complications of COVID-19 than adults, particularly older adults. Many kids who get COVID-19 never even have symptoms. Additionally, kids’ bodies are different, and they may react differently to a vaccine than adults do. But things are moving. Children’s Colorado is participating in a clinical trial investigating the safety and immune response of the Pfizer vaccine in kids ages 5 to 11.

In the meantime, Drs. Brumbaugh and O’Leary encourage families to be patient while waiting for a safe and effective vaccine for younger kids. While we wait, parents should make sure that the whole family is taking precautions to prevent COVID-19, including masks and social distancing, and receives a flu shot, which are now available.

Wondering what you can do when some of the family is vaccinated but younger kids are not? Find our tips on safe activities for unvaccinated kids.

Which vaccines are available?

So far, the FDA has given emergency authorization to three vaccines for COVID-19 and full authorization to one. The first emergency authorization came from pharmaceutical-makers Pfizer and BioNTech, and a second from Moderna followed closely behind. Both of those first vaccines are based on a technology known as mRNA. Both also require two doses, an initial shot and a second dose 3 to 4 weeks later, to be fully effective. On Aug. 23, the FDA granted its full approval to the Pfizer-BioNTech vaccine for people 16 and older, which will now be marketed as Comirnaty.

In early 2021, the FDA issued emergency authorization for a third vaccine from the pharmaceutical company Johnson & Johnson (Janssens). In mid-April, the FDA and CDC paused distribution of the Johnson & Johnson vaccine temporarily while they investigated a potential link to a very rare blood clotting condition. After careful review, the agencies resumed their recommendation of the Johnson & Johnson vaccine with additional guidelines for women younger than 50 years. As of April 23, vaccinations with Johnson & Johnson’s COVID vaccine have restarted with this addition (more on this below).

Unlike the Moderna and Pfizer vaccines, the Johnson & Johnson vaccine can be stored more easily and only requires one dose, rather than the two doses the Moderna and Pfizer vaccines require.

What do they mean by effective?

Clinical trials showed the mRNA-based Pfizer and Moderna vaccines to be more than 90% effective. The Johnson & Johnson vaccine was shown to be 66% effective worldwide, although that figure increased to 72% in the U.S.

It’s important to remember that the term “effective” refers to the vaccines’ ability to prevent all symptomatic infections. But even in cases where someone got sick, in clinical trials all three vaccines were still overwhelmingly effective -- close to 100% -- against severe infection, including hospitalization and death.

What about delta?

Because the delta variant of the coronavirus spreads more easily, we’re now seeing more “breakthrough infections,” where someone who is fully vaccinated gets sick with COVID-19. Fortunately, the chances of a breakthrough infection remain low, especially if you’re taking other precautions like masking indoors. For those who do get a breakthrough infection, the vaccines are still very effective at preventing severe cases that require hospitalization, and deaths.

CDPHE is now reporting breakthrough infections in Colorado on their website. Based on Colorado data from September 28, 2021, people who are fully vaccinated are:

  • 3.3 times less likely to get COVID
  • 5 times less likely to be hospitalized with COVID
  • 5.9 times less likely to die from COVID.

Medical experts are keeping a close eye on breakthrough cases. As we continue to gather scientific data, experts will continue to refine the vaccine recommendations. In the coming months, expect to hear more about timing of doses, booster shots, and additional doses for vulnerable groups – efforts that will enhance the already remarkable protection of authorized vaccines.

What about reports of adverse events?

With any vaccination effort, especially one on this scale, experts expect reports of adverse events. In fact, public health agencies proactively track reports of vaccine side effects using their internal data and surveillance systems and by soliciting reports from members of the public. When they detect a trend or similarities in the types of health events being reported, they investigate and run statistical calculations to determine whether there’s a true association between an adverse event and a vaccine, or if the number of events is expected relative to the size of the population.

Here’s what we know about adverse events potentially associated with the COVID-19 vaccines.

Heart issues and the mRNA vaccines

There have been instances of myocarditis and pericarditis, swelling of the heart muscle and the sac around the heart, in people under 30 who received the Pfizer and Moderna vaccines, including adolescents and teenagers. Current data show that reports of myocarditis and pericarditis after vaccination are slightly more than expected in the population, but very rare. The CDC is evaluating reports of myocarditis closely to understand any association between the vaccine and heart issues.

From what we know so far, these side effects remain extremely rare, and research shows that more than three times as many people developed heart inflammation after contracting COVID-19 than after receiving the vaccines to protect against the virus. According to a study that included more than 800,000 people and was published in the New England Journal of Medicine in late August, there were 2.7 cases of myocarditis per 100,000 vaccinated people, compared to 11 cases of myocarditis per 100,000 people infected with COVID-19.

“These data show that a young person's risk of myocarditis is higher if they get COVID than it is if they get vaccinated,” says Dr. Brumbaugh. “It’s understandable to have concerns about these reports, but keep in mind that myocarditis can be caused by a number of viral infections, including COVID itself.” The CDC continues to recommend the mRNA vaccines given the risk of long-term complications from the coronavirus itself.

Though these reports are understandably concerning to many parents, it helps to put it all in context. Of the patients who did experience myocarditis or pericarditis after their vaccination, all recovered within a few days.

“The good news is that our systems worked – we found this side effect,” says Dr. Dominguez. “We've been able to quantify it and understand the risks around it. But overall, these vaccines have proven to be remarkably safe in the general public.”

What you need to know about myocarditis

Confirmed cases of myocarditis or pericarditis have occurred primarily in male adolescents and young adults age 16 years or older. Typically, these events occurred within several days of vaccination and more often after getting the second dose than after the first dose of one of these two mRNA COVID-19 vaccines. Most patients who received care responded well to treatment and rest and quickly felt better.

After an mRNA COVID vaccination, be on the lookout for any chest pain, shortness of breath or feelings of having a fast-beating, fluttering, or pounding heart. Seek medical care if you think you or your child have any of these symptoms within a week after COVID-19 vaccination.

With any medical intervention, including vaccines, doctors compare the known and potential risks to the known and potential benefits. Medical experts recommend the COVID-19 vaccines because the benefits from vaccination far outweigh the risks, including for these recent reports of myocarditis and pericarditis. Conversely, there are still many unknown risks of contracting COVID-19. And just like with the Johnson & Johnson vaccine, these reports show that our country’s extensive vaccine safety systems are working.

Why was the Johnson & Johnson vaccine paused?

Currently, the Pfizer-BioNTech vaccine is available under both full approval (for people 16 and older) and emergency authorization (for children 12 to 15 and for third doses for certain immunocompromised people), while Moderna and Johnson & Johnson are available under “emergency authorization,” or EUA. EUA is a little different than approval. It’s an important distinction because it reflects the urgency of the pandemic. Not quite as much is known about these vaccines as would ordinarily be known about a drug before full approval, particularly their long-term effects. So medical experts and agencies like the FDA and the CDC have taken a cautious approach.

That’s essentially why authorities chose to pause distribution of the Johnson & Johnson vaccine after the CDC’s alert system identified a rare clotting disorder in a small number of women in the weeks after they received the vaccine.

“In some ways it was an indication that the system is working right,” says Dr. Brumbaugh, “because it gives us the opportunity to see this cluster of cases and understand what happened.”

During the proactive pause, investigators compared the rate at which this clotting disorder occurs in people who received the vaccine versus people who didn’t; they concluded that this adverse event is associated with the Johnson & Johnson vaccine but remains very rare, occurring at a rate of about 7 per 1 million vaccinated women between the ages of 18 and 49. This adverse event is even more rare for women 50 years and older and men of all ages.

“It takes a lot of hours and data crunching to be able to make that determination,” Dr. Brumbaugh says.

What you need to know about the Johnson and Johnson vaccine

The agencies have since updated their vaccine safety guidelines for this subgroup of adults. Women younger than 50 years old should be aware of the rare but increased risk of blood clots with low platelets after vaccination and that this risk has not been seen with the Pfizer and Moderna vaccines. If you have questions about your risk and which vaccine you should get, talk to your doctor.

If you have received (or will receive) the Johnson & Johnson COVID-19 vaccine, three weeks after receiving the vaccine, you should be on the lookout for possible symptoms of a blood clot with low platelets. The CDC has updated details on the Johnson & Johnson vaccine.

Should we expect additional adverse events or pauses?

It’s possible. COVID-19 vaccine safety is a top priority for the government, and reports of health problems following COVID-19 vaccination are taken very seriously.

If you experience any adverse events after any vaccination, report them to v-safe and the Vaccine Adverse Event Reporting System (VAERS). Learn about how vaccine safety systems work.

How we got here

Operation Warp Speed and the successful push for a safe and effective vaccine

Vaccines are a risky proposition for pharmaceutical companies. Only about one in 10 vaccines in development is likely to produce a viable result, and they take a long time to develop. The quickest before COVID-19 took about four years. Most take closer to 10 or 15.

Operation Warp Speed was the U.S. Department of Health and Human Service’s attempt to shatter that timeline, basically by paying six different pharmaceutical companies to give it their best shot – ideally bringing a vaccine to market within a year.

“It’s unprecedented,” says Dr. O’Leary.

A pediatric infectious disease specialist at Children’s Colorado, Dr. O’Leary has himself played an outsized role in the scientific community’s response to the pandemic, as a representative of the American Academy of Pediatrics. He also played a role in the CDC committee that approved and made recommendations on the current available vaccines.

How did the vaccine development happen so fast?

It happened fast for two basic reasons. One was funding. Vaccines cost a lot of money to develop, and because so many of them fail, drug-makers take on a lot of risk developing them. Operation Warp Speed absorbed that risk by paying pharmaceutical companies up front. The U.S. government spent tens of billions of dollars in the hope of helping produce at least one viable vaccine, and hopefully more. The effort paid off.

The other reason was efficiency. It takes a lot of people and organizations to develop and produce a vaccine, and typically, the process involves a lot of waiting: for funding, for supplies, for review processes, and so on. In Operation Warp Speed, the whole process was streamlined.

A pharmaceutical company would also typically wait to see if their vaccine was approved and recommended before beginning to manufacture. Operation Warp Speed, however, paid companies to manufacture their vaccines before it was known if they’d work. So once they were authorized, they were ready to go immediately. Even then, doses are in short supply. But as long as the timeline currently is, it would be a lot longer if Pfizer and Moderna were only starting to ramp up manufacturing now.

To better understand that timeline, it helps to understand what’s happened so far.

What it takes to develop a vaccine

At the most basic level, a virus is really just a tiny wad of genetic code. It gets into the body, attaches to cells and essentially highjacks their mechanisms to reproduce itself. In response, ideally, the immune system makes antibodies that kill the virus off. But in the meantime, the virus can do a lot of damage.

The idea of a vaccine is to prevent the virus from infecting the body in the first place. Vaccines more or less train the body to kill a virus as soon as it comes along, before it does. It’s a complicated process that typically starts with understanding as much as possible about how, specifically, the virus works in bodies. How does it get into cells? How does the immune system react to it?

In the case of COVID-19, there’s a lot scientists still haven’t figured out. For example, multisystem inflammatory syndrome in children, or MIS-C, a dangerous condition that COVID-19 causes in a small number of kids, is probably related to immune response. But scientists don’t know exactly how or why.

On the other hand, there is also a lot that medical experts do understand about this virus, and we’re learning more every day. For example, we knew the genetic code of this virus in January 2020, before many people had even heard of COVID-19. The speed of development, says Dr. O’Leary, speaks to the decades of research on vaccines in general and on coronaviruses specifically that have led us to this moment.

How do clinical trials work?

Viral infection is a molecular process, so once a pharmaceutical developer has a handle on the chemistry, the next step is to test the biology in animals. Both those steps generally take years. But if a vaccine, after much testing, does look safe and effective, eventually it makes the leap to testing in humans.

Those tests are called clinical trials, and they happen in three phases.

Phase one

The big question in phase one is, “Is it safe?” Phase one trials typically involve a small group of people. If the treatment is shown to have harmful effects, the testing ends and everyone goes back to the drawing board.

Phase two

Phase two often involves a randomized control trial, where participants are usually divided into two groups: one gets the treatment being tested; another gets a placebo, or dummy drug. In this phase, researchers are building a better understanding of the treatment’s safety, as well as how and if it works. In the case of vaccines, one of the big questions in phase two trials is if the vaccine generates enough immune response to be effective.

Phase three

The final phase involves the largest group of people, often in the thousands or tens of thousands. This phase seeks to answer, “How effective is it, and how does it work best?” Researchers study how the drug works on people of different ages and medical histories, comparing different doses and frequencies. In the case of a COVID-19 vaccine, the FDA has stated it would approve a vaccine that protects against the virus in at least 50% of people who get it. As with earlier phases, safety remains of paramount concern.

How does a new vaccine get approved?

The FDA: approval

If a potential treatment is shown through clinical trials to be safe and effective, the pharmaceutical company then submits all their trial data to the FDA. The FDA reviews the data and decides whether to approve the treatment — meaning it decides whether the company can sell the treatment to the public. This process alone typically takes at least a year.

In addition to internal review by staff at the FDA, the FDA also has an external group of experts called the Vaccines and Related Biological Products Advisory Committee, or VRBPAC for short. The committee consists of 15 outside experts in virology, epidemiology, biostatistics, microbiology and about a dozen other related disciplines. All of its members are thoroughly vetted for potential conflicts of interest and are not beholden to political interests. In general, without the VRBPAC approval, the FDA doesn’t approve.

The CDC: recommendation

If the FDA approves of a new vaccine, it then goes to the CDC, which decides whether to recommend it in the U.S., and for whom. This step is an important one for vaccines, since healthcare plans are required to cover vaccines with no deductible under the Affordable Care Act. That coverage doesn’t happen without a CDC recommendation.

Like the FDA, the CDC has a review process conducted by a panel of vetted outside experts removed from political pressure, this one called the Advisory Committee on Immunization Practices, or ACIP. That’s the one Dr. O’Leary is a part of, as a representative of the American Academy of Pediatrics and the Pediatric Infectious Diseases Society. Their meetings are free and open to the public, if you’re so inclined.

The Pfizer, Moderna and Johnson & Johnson vaccines have already gone through that entire rigorous process — and any other vaccines that might be approved in the future will go through it too.

How do mRNA vaccines work?

Both Pfizer’s and Moderna’s vaccines employ a technology called messenger RNA. Where traditional vaccines have generally used inactivated parts of the infectious virus to prime the immune system to respond to it, messenger RNA, or mRNA, actually tells cells what to build inside themselves. The vaccination works essentially by introducing a bit of code that tells cells how to protect themselves against a virus.

The advantage of mRNA vaccines is that they’re faster and cheaper to produce. And since they aren’t made using infectious elements, they’re potentially safer for patients. The possible downside? Vaccines employing mRNA may need to be stored at incredibly cold temperatures — close to 100 degrees below zero, Fahrenheit — which has presented logistical challenges when it comes to distribution.

Pfizer’s vaccine was the first mRNA-based treatment ever authorized, and Moderna’s was the second.

Do I need to get vaccinated if I’ve already had COVID-19?

The clinical trials from all three vaccines showed that they’re safe for people who have already had COVID-19, so the current thinking is that people should get vaccinated, when possible, regardless of whether they’ve had it or not, although it should wait until they’ve recovered. (If someone were to get the virus after their first vaccine dose while waiting for the second, they should wait until after they’ve recovered to get the second shot.)

That said, the most up-to-date evidence also suggests that reinfection is uncommon for about 90 days after the initial infection, so people might wait to get vaccinated until near the end of that period — if they want to.

Are these COVID-19 vaccines safe?

Vaccines have historically been remarkably safe and effective, and our experts believe all three currently available vaccines — along with any other vaccines that might be authorized — are no different.

That’s because, although the process has been accelerated, no corners are being cut. All three vaccines went through every single step of the vast, rigorous and complex process required to understand the safety and effectiveness of any new vaccine.

"This didn’t just happen in a year. This work is built on decades of remarkable progress in the development of vaccines,” says Dr. O’Leary. “I think we have many reasons to trust the process."

That goes not just for COVID-19 vaccines, but for the many other vaccines available. Dr. O’Leary notes that general vaccination rates for kids have recently declined, potentially because families are avoiding healthcare providers’ offices due to the pandemic.

That would be a mistake, Dr. O’Leary says. Vaccines are the single best way to prevent disease: Kids need them to stay safe. That’s especially true this year, when COVID-19 has the potential to complicate other diseases in ways that are difficult to anticipate — including influenza. Dr. O’Leary urges families to make sure kids get their flu shot as soon as they become available.

As for the COVID-19 vaccines, it may be a while before they’re available for all ages. And the pandemic isn’t over. The highly contagious delta variant is spreading fast and causing increased case counts and hospitalizations, particularly in areas with low vaccination rates. Until you are fully vaccinated (2 weeks after your last dose) and even once you are fully vaccinated, there’s still every reason to take precautions like social distancing and wearing masks—especially indoors.

There’s a light at the end of the tunnel, but reaching it depends on all Americans who can get vaccinated following through with the lifesaving immunizations.

“I’m optimistic,” Dr. O’Leary says. “I’m hopeful that as more vaccines are fully approved and authorized for people of all ages, we will be able to contain COVID-19 and continue working toward an end to the pandemic.”

Trustworthy sources on the COVID-19 vaccines


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