Alabama health officials are urging schools to continue requiring masks despite a decline in COVID-19 cases in the state, which has one of the nation’s lowest vaccination rates and worst death rates.

The state department of public health said Tuesday nearly 23% of COVID infections in Alabama are among children up to the age of 17. As of Monday, at least 30 children were hospitalized for the disease, and three were on ventilators.

“Consistent and correct mask use in schools has helped reduce the number of cases of COVID-19, helped schools remain open to in-person learning in Alabama, and helped prevent the consequences of this serious disease,” the department said in a news release.

The release cited studies by the U.S. Centers for Disease Control and Prevention that found masks were critical to preventing the spread of COVID-19 in schools.

Alabama left masking decisions to local officials, resulting in a patchwork of rules that vary in districts just a few miles apart. While Birmingham city schools require face masks, nearby Vestavia Hills dropped its mandate and made face masks optional last week. Shelby County has said it will quit requiring facial coverings at the end of the month.

Alabama has had 14,155 deaths related to COVID-19, according to researchers from Johns Hopkins University. The death count is the 16th highest in the country overall and the fourth highest per capita at nearly 290 deaths per 100,000 people.

Health officials attribute much of the problem to Alabama’s vaccination rate, which the Centers for Disease Control and Prevention ranks worst in the Southeast and among the lowest in the nation. Roughly 42% of the state’s population is fully vaccinated.

Over the past two weeks, the rolling average number of daily new cases has decreased by 1,397, a drop of about 36%, and hospitalizations have fallen below 1,500 after reaching nearly 2,900 on Sept. 1.

Even with the improvement, Alabama ranked 10th nationally for the rate of new cases over the past week. There were 785 new cases per 100,000 people in Alabama over the past two weeks, according to Johns Hopkins.