"With most of the 1.5 million children in grades K-12 now having returned to in-person instruction, Public Health is encouraged that case rates have not increased," the county public health department said in a news release.
"The decreases are similar to the decreases seen among adult residents and occurred as many schools reopened with testing, masking, infection control and outbreak management protocols in place."
According to county statistics, between Aug. 15 and Sept. 13, 7,995 COVID infections have occurred among the roughly 1.5 million students in the county, about .5%, which is only slightly higher than the general county infection rate of 0.4%.
The vast majority of the infections, 5,456, occurred among students in the Los Angeles Unified School District, the largest in the county and second-largest in the nation.
Positive cases among school staff are at .7%.
Ferrer said vaccines are the only way out of the pandemic and the best way to limit disruptions in schools.
"One major advantage of being vaccinated is that fully vaccinated students are more likely to be able to stay in school after an exposure without a quarantine," Ferrer said.
With the rate of COVID-19 infections dropping even after a return to in-person learning, L.A. County health officials announced Thursday modified quarantine rules for unvaccinated students exposed to COVID-19 that would allow them to continue attending in-person classes under select circumstances.
The optional "modified quarantine" system is available to unvaccinated students whose exposure to an infected person occurred when both were fully masked. The unvaccinated student also must not be displaying any symptoms of infection.
According to Ferrer, the unvaccinated student who meets those basic conditions can continue to attend in-person classes, but must remain asymptomatic and must wear a mask at all times. The student also must quarantine at home at all times other than while at school.
The student will have to be tested twice a week during the quarantine period, including once within one or two days of the exposure and again at least three days after the exposure. The modified quarantine period can end after seven days if the student tests negative at least five days after being exposed.
Ferrer said school districts are not required to offer the modified quarantine, noting that schools would have to have the necessary resources to enforce all of its requirements. She conceded that it could also be difficult in some cases to verify that the exposure occurred when both the unvaccinated student and the infected person were both wearing masks at all times.
The modified quarantine procedure is only available for students, not teachers. The procedure also cannot be used in cases of a confirmed COVID outbreak at a campus.
Ferrer identified risky behavior, such as not masking, using masks incorrectly, students sitting facing each other and different teams sharing weight rooms at the same time.
All LAUSD students eligible to get the vaccine are required to be fully vaccinated by Jan. 10. District employees must also be vaccinated.
City News Service contributed to this report.