Please assess the completion status of the following clinical trial:

Trial Title: An Immunity Persistence Study of Sabin Inactivated Poliovirus Vaccine(Vero Cell) After Four Doses

Study Design Characteristics:
- Allocation: None
- Intervention Model: None
- Observational Model: OTHER
- Primary Purpose: None
- Time Perspective: PROSPECTIVE
- Masking: None
- Phase: None
- Number of Arms: None

Eligibility Criteria:
Inclusion Criteria:~* Subjects who have received 4 doses of experimental vaccine or control vaccine in phase Ⅲ clinical trials~Exclusion Criteria:~* History of vaccination of other vaccine with poliovirus antigenic components except that of phaseⅢ clinical trial.

- Gender: ALL
- Minimum Age: 48 Months
- Maximum Age: 84 Months
- Healthy Volunteers: None

Study Arms:
- Experimental Group (Type: None): Subjects who have received 4 doses of the experimental vaccine (including subjects at the age of 4 years (48 to 54 months) and 5 years (78 to 84 months) after the last vaccination ) will be collected venous blood about 3.0ml.
- Control Group (Type: None): Subjects who have received 4 doses of control vaccine (including subjects at the age of 4 years (48 to 54 months) and 5 years (78 to 84 months) after the last vaccination ) will be collected venous blood about 3.0ml.

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