Please assess the completion status of the following clinical trial:

Trial Title: Different Doses of Vitamin D and T Regulatory Cells in Preterm Infants

Study Design Characteristics:
- Allocation: RANDOMIZED
- Intervention Model: PARALLEL
- Observational Model: None
- Primary Purpose: TREATMENT
- Time Perspective: None
- Masking: QUADRUPLE
- Phase: PHASE1
- Number of Arms: 2.0

Eligibility Criteria:
Inclusion Criteria:~* Preterm infants with gestational age 28-33 weeks~Exclusion Criteria:~* Necrotizing enterocolitis~* Bowel perforation~* Chromosomal anomalies~* Inborn errors of metabolism~* Major congenital anomalies

- Gender: ALL
- Minimum Age: None
- Maximum Age: 28 Days
- Healthy Volunteers: f

Study Arms:
- Low dose (Type: EXPERIMENTAL): Subjects in this group receive 400 IU vitamin D daily for 4 weeks.
- High dose (Type: EXPERIMENTAL): Subjects in this group receive 800 IU vitamin D daily for 4 weeks.

Based on this trial design, predict the completion outcome and termination type (if applicable).