Baltimore school officials are warning parents that their children will be prohibited from attending school starting next week if they have not received immunizations for certain diseases.
The policy could mean that thousands of students will be barred from classes.
Neighboring Baltimore County barred hundreds of children from school this week after failing to meet a Tuesday deadline for required vaccinations. Officials in other districts reported varying numbers of students out of compliance.
Baltimore schools CEO Sonja Santelises said Monday is the deadline for city students' vaccination records to be updated. She said students who fail to meet the deadline risk losing learning time.
"I cannot stress too strongly how important this is," Santelises told the city school board Tuesday night.
The district found roughly 5,000 immunization records that were out of compliance this week, but officials said the number had dropped to about 3,800 by Wednesday morning.
Officials launched an aggressive campaign this year to spread the word about new requirements for students in kindergarten, first, second, and seventh through ninth grades.
School officials said the highest levels of non-compliance were among children in kindergarten, and ninth and seventh grades.
This year's requirements for entry into kindergarten, first and second grades include two doses of Varicella vaccine, which protects against chicken pox.
Students entering seventh through ninth grades are required to have one dose of Tdap vaccine, which protects against the bacterial diseases tetanus, diphtheria and pertussis, and one dose of Meningococcal vaccine, which protects against meningitis.
Officials said that most students were missing Tdap and meningococcal vaccines.
They recommended parents get their children immunized at local pharmacies, or at schools with on-site health centers where the shots are available free.
State law allows school districts to offer families a 20-day grace period from the first day of school to provide immunization records. The number of vaccinations that students require depends on age and grade level.
In Baltimore County, school officials said that nearly 600 students were excluded from school this week because their records were not up to date.
The vast majority of students were middle and high schoolers who need the Tdap and the meningococcal vaccine, county schools spokesman Mychael Dickerson said.
A little more than 100 elementary school students were out of compliance, he said. These were primarily pre-kindergarten and kindergartners who were starting school for the first time.
"We are working closely with the health department to provide vaccines to students who remain excluded from school," Dickerson said.
In Anne Arundel County 89 public school students were out of compliance on Wednesday, the deadline for exclusion from school, according to the county health department, which runs the schools' health program.
In Harford County, the number of students who have not been immunized is "a moving target right now; we do not have a number," said Joseph Licata, the district's chief of administration.
He said students who have not been immunized have been prohibited from attending classes in the past, but he did not say if any had been barred this week.
Filipa Gomes, director of health services for Carroll County Public Schools, said she did not have an exact count of students who are not vaccinated, but she believed the number to be fewer than 40.
"In a lot of these situations the students have the immunizations; we just haven't received the records from the parents," she said. "Once they got the call from the school principal, 'We need your records.' all of a sudden a lot of them came in."
Kerrie Wagaman, the Howard County system's coordinator of health services, could not say how many students needed to provide vaccination information, but said the number was likely low.
The county requires students or parents to provide schools with records proving vaccination on the first day of school, or confirmation of an appointment to complete the immunizations within 20 calendar days of the first day of school.
Students who do not meet the requirement are barred from class.
"Parents can tell us verbally that they have an appointment," Wagaman said. "It doesn't have to be in writing, because it's kind of on the honor system."
Administrators typically remove these students from class on the first day of school and put them in a cafeteria, media center or health room while their parents are called.
"I find that the more firm you are from the first day of school with implementing the policy, compliance with it becomes more consistent across all levels," Wagaman said.
The Baltimore health department has been providing vaccinations at clinics throughout the city for the past several weeks. The To Immunize Kids Everywhere clinics provide vaccinations to families who don't have health insurance, a medical provider or Medicaid.
Health department spokesman Sean Naron said the health department works closely with the school system to make sure students are immunized, in part because many vaccines are administered over several years.
"This may seem like a sprint, but it's really a marathon," Naron said. "We think we're continuing a good track record."
Baltimore Sun Media Group reporters Lisa Philip, Jon Kelvey and Cindy Huang contributed to this article.