Children aged 5 to 11 may be eligible for a coronavirus vaccine by the time they go trick or treating on Halloween.

Pfizer and BioNTech announced Monday its vaccine has been shown to be safe and highly effective among children in that age group. The companies plan to apply to the Food and Drug Administration by the end of the month for emergency authorization to use the vaccine in these children.

The announcement is sure to bring relief for parents and teachers who have been waiting for young children to get vaccinated. Health officials report 8.8% of 5 to 11-year-olds in the county have tested positive for COVID-19. Though case rates have been falling even as children have returned to school.

Unvaccinated children, even if they are asymptomatic, can spread the virus to family members, teachers and others who they are in regular contact with.

Pfizer and BioNTech plan to receive the results of its vaccine trial in children under 5 by the end of the year.

The emergency approval for 5- to 11-year-olds could come swiftly if the process goes as smoothly as it did for other age groups.

Emergency approval for the Pfizer vaccine for people aged 16 and older and children 12 to 15 years old both took three weeks. The FDA has yet to provide full approval of the Pfizer vaccine for children aged 12 to 15. But they can still receive the vaccine under emergency use authorization.

The decision comes at a time when pediatric cases of COVID-19 nationally are on the rise. National data show more than 5 million cases of COVID-19 have been reported among children and teens, causing 460 deaths since the start of the pandemic. Pediatric cases now account for 1 in 5 new cases.

Pfizer's announcement could have big implications for the Los Angeles Unified School District, which was the first major school district in the nation to mandate vaccines for eligible students.

Students who are 12 and older are required to be vaccinated by Jan. 10. It is unclear if the district will extend the mandate to all students 5 and older if the vaccine is given emergency use approval.

The district has established a robust system for administering vaccines. In August, mobile vaccination teams visited every middle and school to administer first and second doses and vaccine appointments can be scheduled through the district's Daily Pass app, which was made by Microsoft. The district has not said whether they would provide vaccines for younger children, if the approval comes.

The full data from the vaccine trial for 5- to 11-year olds has not yet been published or peer reviewed. It will be studied by regulators to determine whether the vaccine is safe and effective.

"We are eager to extend the protection afforded by the vaccine to this younger population, subject to regulatory approval, especially as we track the spread of the Delta variant and the substantial threat it poses to children," Pfizer chief executive Albert Bourla said in a statement. "Since July, pediatric cases of COVID-19 have risen by about 240 percent in the U.S. — underscoring the public health need for vaccination."

There were nearly 2,300 children between ages 5 and 11 in Pfizer's trial, two-thirds of whom received the vaccine.

In the trial, children who received two shots of a 10 microgram dose, spaced three weeks apart had similar side effects to young adults. People 12 and older receive a 30 microgram dose.