That’s a big “if,” which depends on factors such as the timeline for COVID clinical trials that involve children, the actual results of those clinical trials, and the regulatory standards that would guide an authorization or approval.

Vaccine trials have already begun, or are about to begin, in children as young as 6 in some countries. And Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID), believes it’s possible for children as young as 6 to begin getting the vaccine by September, around the start of the next school year.

But there’s plenty of work to be done before achieving that goal. Here’s where we are on opening up vaccine eligibility to children.

Different COVID vaccines are in different stages of children’s clinical trials

The Food and Drug Administration (FDA) has two main criteria for deciding whether or not a therapy or vaccine should be authorized or approved: safety and efficacy. And in the coming months, a variety of COVID vaccines from Pfizer/BioNTech’s to Moderna’s to AstraZeneca’s will tested on those fronts in an increasingly younger patient age group.

Pfizer and Moderna, the firms with the only two FDA emergency authorized vaccines in the U.S. to date, have already begun the process of enrolling teens into clinical trials, although it will take months to get tangible data. Pfizer, which has completed its initial enrollment process, expects to have data for 12- to 15-year-olds in the spring after beginning the trials in earnest by the end of March.

Then it will focus on conducting trials in children as young as first graders. Finally, the FDA regulatory and authorization process could take several more weeks before a rollout can begin. If everything pans out, that could theoretically set Pfizer up for an authorization in younger Americans before the fall school year. Johnson & Johnson also plans to launch pediatric trials in March.

Moderna is further behind in the effort. The firm is still recruiting teenage participants for its own vaccine trials and may provide data by this summer; for younger groups, however, the trial process will likely take until early 2022. And then there’s AstraZeneca, which is working with Oxford University and launching the first-ever COVID vaccine trial in the world for children younger than 12 this month in the U.K.

Why this so-called de-escalation approach to children’s vaccines? A pharmaceutical product won’t affect everyone in the exact same way. That’s why treatments typically get the green light on a sliding scale. First, a biopharmaceutical may be approved for a certain demographic group with a certain version of a disease; afterward, the product label may be expanded to encompass a wider swath of the population.

Adults tend to be the first subjects enrolled in clinical trials (unless a drug is specifically tailored toward a childhood disease, and even then there are special protocols and guidelines). And for good reason. The immune system and biological complexities of a 6-year-old will be different from that of a 12-year-old or 16-year-old, and significantly different from a much older person.

That’s just for usual therapeutics. Things are more nuanced when it comes to a rapid vaccine rollout. So far, preliminary results suggest the existing class of vaccines is, at the very least, safe, although more rigorous data is necessary. But there’s still a way to go before we know how robust a coronavirus immune response is in vaccinated children.

How COVID affects children

The crucial goal of bringing school systems back to a semblance of normalcy is just one reason why the child vaccination push is important. Achieving herd immunity and preventing community spread of the virus is also critical.

Contrary to suggestions that only old and sick people can contract COVID, kids can get it too. But it may manifest in very different ways from adults who get seriously ill. “Most children who become infected with the COVID-19 virus have only a mild illness,” according to the Mayo Clinic.

Many coronavirus-carrying kids can also be asymptomatic. While the exact number is still unknown, previous studies have suggested that up to a third of child carriers may be asymptomatic while still being able to transmit the infection. A January study by the Centers for Disease Control (CDC) finds that nearly 60% of COVID transmissions are caused by people without symptoms.

Vaccine makers will have to be careful on double-checking the safety and efficacy data in the coming months and will face practical hurdles such as the relative difficulty of getting children enrolled in experimental trials. But the educational and public health imperatives highlight why this will be a critical step in the battle against COVID.