Please assess the completion status of the following clinical trial:

Trial Title: A Booster Dose of Inactivated Vaccine (Vero Cell) Against EV71 in Chinese Children

Study Design Characteristics:
- Allocation: RANDOMIZED
- Intervention Model: PARALLEL
- Observational Model: None
- Primary Purpose: PREVENTION
- Time Perspective: None
- Masking: TRIPLE
- Phase: PHASE2
- Number of Arms: 8.0

Eligibility Criteria:
Inclusion Criteria:~* Had participated in the previous phase II trial and received at least 1 dose of EV71 vaccine.~* Healthy children as established by medical history and clinical examination~* The subjects' guardians are able to understand and sign the informed consent~* Subjects who can and will comply with the requirements of the protocol~* Subjects with temperature \<=37.0°C on axillary setting~Exclusion Criteria:~* Had participated in the previous phase II trial and received placebo.~* Subject who has a medical history of EV71-associated disease with specific laboratory evidence~* \<= 37 weeks gestation~* Subjects with a birth weight \<2.5 kg~* Subject that has a medical history of any of the following: allergic history, or allergic to any ingredient of vaccine~* Family history of seizures or progressive neurological disease~* Family history of congenital or hereditary immunodeficiency~* Severe malnutrition or dysgenopathy~* Major congenital defects or serious chronic illness, including perinatal brain damage~* Autoimmune disease~* Bleeding disorder diagnosed by a doctor or significant bruising or bleeding difficulties with IM injections or blood draws~* Any acute infections in last 7 days~* Any prior administration of immunodepressant or corticosteroids in last 6month~* Any prior administration of blood products in last 3 month~* Any prior administration of other research medicines in last 1 month~* Any prior administration of attenuated live vaccine in last 14 days~* Any prior administration of subunit or inactivated vaccines in last 7 days, such as pneumococcal vaccine~* Under the anti-TB prevention or therapy~* Any condition that in the opinion of the investigator, may interfere with the evaluation of study objectives

- Gender: ALL
- Minimum Age: 21 Months
- Maximum Age: 51 Months
- Healthy Volunteers: f

Study Arms:
- alum-adjuvant 160U /0.5ml EV71 vaccine (Type: EXPERIMENTAL): A booster dose of alum-adjuvant 160U /0.5ml EV71 vaccine in 160 children whom had received two doses of alum-adjuvant 160U/0.5ml EV71 vaccines one year before.
- placebo A (Type: PLACEBO_COMPARATOR): A 0/0.5ml placebo in 80 children whom had received two doses of alum-adjuvant 160U/0.5ml EV71 vaccines one year before.
- alum-adjuvant 320U /0.5ml EV71 vaccine (Type: EXPERIMENTAL): A booster dose of alum-adjuvant 320U /0.5ml EV71 vaccine in 160 children whom had received two doses of alum-adjuvant 320U/0.5ml EV71 vaccines one year before.
- placebo B (Type: PLACEBO_COMPARATOR): A 0/0.5ml placebo in 80 children whom had received two doses of alum-adjuvant 320U/0.5ml EV71 vaccines one year before.
- alum-adjuvant 640U /0.5ml EV71 vaccine (Type: EXPERIMENTAL): A booster dose of alum-adjuvant 640U /0.5ml EV71 vaccine in 160 children whom had received two doses of alum-adjuvant 640U/0.5ml EV71 vaccines one year before.
- placebo C (Type: PLACEBO_COMPARATOR): A 0/0.5ml placebo in 80 children whom had received two doses of alum-adjuvant 640U/0.5ml EV71 vaccines one year before.
- adjuvant-free 640U /0.5ml EV71 vaccine (Type: EXPERIMENTAL): A booster dose of adjuvant-free 640U /0.5ml EV71 vaccine in 160 children whom had received two doses of adjuvant-free 640U/0.5ml EV71 vaccines one year before.
- placebo D (Type: PLACEBO_COMPARATOR): A 0/0.5ml placebo in 80 children whom had received two doses of adjuvant-free 640U/0.5ml EV71 vaccines one year before.

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

Answer: outcome: complete