The US could authorize COVID-19 vaccines for younger kids around Halloween, Pfizer's new timeline suggests

• On Thursday, Pfizer asked the FDA to authorize its COVID-19 shot for kids ages 5 to 11.
• That means kids could start getting vaccinated sometime around Halloween.
• The FDA could OK vaccines for kids ages 6 months to 5 years in November, Pfizer's timeline suggests.

Vaccines for kids have finally entered the home stretch.

Pfizer asked the Food and Drug Administration on Thursday to authorize a lower dose of its COVID-19 vaccine for kids ages 5 to 11 after data last month showed the shot was safe and effective among this age group.

The FDA could greenlight the shot for young kids sometime around Halloween, since the data take weeks to review.

Vaccines for even younger children could be close behind. Pfizer expects to produce trial data for kids between 6 months and 5 years old as soon as this month, the company said in a press release. During an investor conference last month, Pfizer's chief financial officer, Frank D'Amelio, said the company would likely submit that data to the FDA in early November, putting it on track for authorization in late November.

Moderna, meanwhile, said it expected to have data about its vaccine's efficacy among kids ages 6 to 12 later in the fall or early in winter. Morgan Stanley analysts recently estimated that Moderna's timeline was one or two months behind Pfizer.

Moderna data for kids 6 months and older would then be available in late 2021 or early 2022, the analysts said.

Johnson & Johnson is on a slower timeline. The company won't start studying its vaccine among children ages 12 to 17 until later this fall at the earliest. If the shot is shown to be safe and effective among those kids, J&J can then start enrolling 2- to 11-year-olds in its trial, followed by children younger than 2. That means a single-dose shot likely won't be available to kids until sometime in 2022.

Vaccines can reduce severe disease among young kids

A recent study from the Centers for Disease Control and Prevention found that unvaccinated adults in the US were 11 times more likely to die and 10 times more likely to be hospitalized from COVID-19 than those who were fully vaccinated. In addition to offering kids protection, vaccinating them will probably make it harder for the virus to spread in the general population - particularly now that in-person school is in full swing.

"Our fundamental problem is we don't have enough adults immunized right now, and we don't have approval for the kids," Chris Beyrer, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health, told Insider. "Until that changes, we're going to have ongoing transmission, unacceptably high rates."

Right now, 65% of all Americans are fully vaccinated. If all 48 million children under 12 got vaccinated in the US, that figure would rise to nearly 80%.

Young children may receive a lower dose

Since the FDA has fully approved Pfizer's vaccine for people 16 and older, pediatricians can legally prescribe the shot for "off-label" use in young kids. But health officials have said not to do so yet.

Children tend to develop more intense side effects after vaccines than adults, likely because their immune systems rev up quickly. So Pfizer and Moderna are each testing a lower dose of their vaccines among kids to avoid unnecessary side effects.

Pfizer's late-stage trial indicates that the lower dose - 10 micrograms, instead of the 30 given to adults - was safe among nearly 2,300 children ages 5 to 11. The trial also demonstrated that the vaccine produced a strong antibody response among younger kids. These results were comparable to the ones observed among people ages 16 to 25, who received the standard 30 micrograms, Pfizer said.

The trial is administering an even smaller dosage, 3 micrograms, to children ages 6 months to 5 years.

Moderna is similarly comparing its standard dose (100 micrograms) with lower doses for all age groups. Children ages 2 to 12 in the trial are receiving either 50 or 100 micrograms, and kids between 6 months and 2 years old are receiving 25, 50, or 100.

This story has been updated with new information. It was originally published September 15.