Great news, but with a couple of caveats. In a release this morning, Pfizer declared that a trial involving 2,000 children between ages 12 and 15 showed its vaccine to be 100% effective against COVID-19 infections. That’s an even better rate than its previous Phase 3 trials among adults, in an environment with more variants in the mix to boot. With the FDA already allowing Pfizer vaccinations at 16 years and up, the news could touch off the next phase of the battle to end the pandemic — with middle and high schools as the battlegrounds.

So what’s the catch?

NEW: Pfizer says their COVID-19 vaccine works for people as young as age 12, according to early test results.#Pfizer says it tested more than 2,000 volunteers, aged 12 to 15, and found none of them got COVID. pic.twitter.com/9bOkzCi01m

— CBS This Morning (@CBSThisMorning) March 31, 2021

The Pfizer-BioNTech coronavirus vaccine is extremely effective in adolescents 12 to 15 years old, perhaps even more so than in adults, the companies reported on Wednesday. No infections were found among children who received the vaccine in a recent clinical trial, the drug makers said; the children produced strong antibody responses and experienced no serious side effects.

The findings, if they hold up, may speed a return to normalcy for millions of American families. Depending on regulatory approval, vaccinations could begin before the start of the next academic year for middle school and high school students, and for elementary school children not long after.

The companies announced the results in a news release that did not include detailed data from the trial, which has not yet been peer-reviewed nor published in a scientific journal. Still, the news drew praise and excitement from experts.

“Oh my god, I’m so happy to see this — this is amazing,” said Akiko Iwasaki, an immunologist at Yale University. If the vaccines’s performance in adults was A-plus, the results in children were “A-plus-plus.”

It’s great news, but it’s great news in progress. Pfizer’s release is an update in an ongoing process; the data has yet to undergo peer review, let alone FDA scrutiny. And the size of the trial (2,260 overall subjects) seems a bit low for the FDA’s purposes. Even as a whole it doesn’t seem large enough to be clinically representative, let alone have enough people in the necessary demographic categories to get any conclusory results in regard to sex, ethnicity, co-morbidities, etc. The New York Times report suggests that this is one component of a larger series of trials, which makes more sense — and would make this preliminary.

The same is true for the other point Pfizer made on vaccine tolerance among this age cohort:

BREAKING: Pfizer COVID vaccine "well-tolerated" in trial of 12-15 year-olds.@megtirrell reports: pic.twitter.com/5oTDnwhztD

— Squawk Box (@SquawkCNBC) March 31, 2021

“Well tolerated” means minimal side effects, which is also good news. However, this trial only injected the vaccine into 1,130 patients if this trial was constructed in the traditional double-blind manner used by the FDA. Side effects sometimes don’t make an appearance until much broader Phase 3 testing, which usually involves a lot more people in both the test and control groups. Finally, in this small group, Pfizer might have difficulty telling just how much the vaccine works as opposed to the more difficult uptake COVID-19 has among children and teens. The infection rate in the control group only amounts to 1.6%, which seems pretty low generally for COVID-19.

That doesn’t make this news bad or even a disappointment, of course. It just means it looks preliminary. Here’s hoping the rest of the data looks this good.