Dive Insight:

In recent weeks, the U.S. vaccination campaign has shifted. Everyone 18 and older is now eligible, and at least nine states have at least partially vaccinated 70% of their adult population, a key threshold for achieving herd immunity against the virus.

Nationwide, some 40% of the country is fully vaccinated, according to data from the Centers for Disease Control and Prevention. Infections and deaths from COVID-19 have fallen to levels not seen since last spring.

Making multiple vaccines available to adolescents and, ultimately, children is the next step, particularly as families consider summer camps and look ahead to the next school year. Since Pfizer’s vaccine was cleared for use in young teens two weeks ago, more than 2 million adolescents between 12 and 15 years old have received a shot, according to CDC data.

Vaccinating teens and children, however, has brought new debate. The U.S. now has more vaccine supply than it needs while many other countries are still struggling to contain the virus. Infections and severe COVID-19 are less common in younger children than they are in older adults. Some — including the head of the World Health Organization — argue that any excess supply in wealthier countries should be donated to nations with less access instead.

Children are still at risk of infection and serious disease, particularly those with existing medical conditions. Younger people can also spread the disease to those more susceptible to its most serious effects. Outbreaks can lead to school closures. Many of those issues were on the minds of the CDC advisers who recently voted to recommend adoption of Pfizer’s vaccine in 12- to 15-year-olds.

“This is a really important issue for this summer,” said Camille Kotton, an infectious disease doctor at Massachusetts General Hospital and a panelist, at the meeting earlier this month. “This is another way to get closer to ending this horrible pandemic.”

Moderna’s vaccine could be next. The company had suggested a strongly positive result from its study earlier this month. More detailed findings on Tuesday showed the shot was between 93% to 100% effective at preventing COVID-19. The exact efficacy depends on how cases are defined. By the definition Moderna used in the study that led to its vaccine’s authorization in adults — which included multiple symptoms and a positive test — 4 cases occurred in the placebo group and none in vaccinated participants 14 days after the second dose.

The company calculated 93% efficacy two weeks after the first dose when using the CDC’s stricter definition, which counts cases with only one symptom. Moderna didn’t provide the breakdown of cases for each group by this measure, but the company plans to publish the data in a peer-reviewed journal.

As with other trials of Moderna’s shot, the most common side effects were pain at the injection site, headache, fatigue and chills that were mild to moderate in degree. Safety monitoring will continue for 12 months after the second dose.

A study in children aged six months to 11 years old, called KidCOVE, began in March and is ongoing. The FDA has scheduled a panel in June to discuss the data needed to consider authorizing shots in children under 12.