Please assess the completion status of the following clinical trial:

Trial Title: Safety and Immunogenicity Study of Inactivated Vaccine for Prevention of SARS-CoV-2 Infection(COVID-19)

Study Design Characteristics:
- Allocation: RANDOMIZED
- Intervention Model: PARALLEL
- Observational Model: None
- Primary Purpose: PREVENTION
- Time Perspective: None
- Masking: DOUBLE
- Phase: PHASE1/PHASE2
- Number of Arms: 4.0

Eligibility Criteria:
Inclusion Criteria:~* Healthy adults aged ≥60 years;~* Be able to understand and sign the informed consent voluntarily;~* Provide legal identification;~Exclusion Criteria:~* Travel / residence history of Wuhan city and surrounding areas or other communities with case reports within 14 days prior to the enrolment;~* Contact with SARS-CoV-2 infected persons (positive for nucleic acid detection) within 14 days prior to the enrolment;~* Contact patients with fever or respiratory symptoms from Wuhan city and surrounding areas, or from communities with case reports within 14 days prior to the enrolment;~* Two or more cases of fever and / or respiratory symptoms in a small contact area of subjects, such as family, office, school class or other places within 14 days prior to the enrolment;~* History of SARS;~* History of SARS-CoV-2 infection;~* History of asthma, allergy to vaccines or vaccine ingredients, and serious adverse reactions to vaccines, such as urticaria, dyspnea, angioneuroedema;~* Congenital malformation or developmental disorder, genetic defect, severe malnutrition, etc;~* Autoimmune disease or immunodeficiency / immunosuppression;~* Serious chronic disease, serious cardiovascular disease, hypertension and diabetes that cannot be controlled by drugs, hepatorenal disease, malignant tumor, etc;~* Serious nervous system disease (epilepsy, convulsion or convulsion) or psychosis;~* Thyroid disease or history of thyroidectomy, asplenia, functional asplenia, asplenia or splenectomy resulting from any condition;~* Diagnosed abnormal blood coagulation function (eg, lack of blood coagulation factors, blood coagulopathy, abnormal platelets) or obvious bruising or blood coagulation;~* Immunosuppressive therapy, cytotoxic therapy, inhaled corticosteroids (excluding allergic rhinitis corticosteroid spray therapy, acute non-complicated dermatitis superficial corticosteroid therapy) in the past 6 months;~* Long history of alcohol or drug abuse;~* Receipt of blood products in the past 3 months;~* Receipt of other investigational drugs in the past 30 days;~* Receipt of attenuated live vaccines in the past 14 days;~* Receipt of inactivated or subunit vaccines in the past 7 days;~* Acute diseases or acute exacerbation of chronic diseases in the past 7 days;~* Axillary temperature \>37.0°C;~* According to the investigator's judgment, the subject has any other factors that are not suitable for the clinical trial.

- Gender: ALL
- Minimum Age: 60 Years
- Maximum Age: None
- Healthy Volunteers: t

Study Arms:
- Experimental Vaccine-medium dosage (Type: EXPERIMENTAL): 24 participants in medium-dosage group in phase Ⅰ will receive two doses of primary immunization according to the immunization schedule of day 0, 28 and will receive 1 dose of booster immunization 1 year after primary immunization; 100 participants in medium-dosage group in phase Ⅱ will receive two doses of primary immunization according to the immunization schedule of day 0,28 ,1 dose of booster immunization 6 months after primary immunization(the third dose ) and the second booster dose (the fourth dose) 1 year after the second dose.
- Experimental Vaccine-high dosage (Type: EXPERIMENTAL): 24 participants in high-dosage group in phase Ⅰ will receive two doses of primary immunization according to the immunization schedule of day 0, 28 and will receive 1 dose of booster immunization 1 year after primary immunization; 100 participants in high-dosage group in phase Ⅱ will receive two doses of primary immunization according to the immunization schedule of day 0,28 ,1 dose of booster immunization 6 months after primary immunization(the third dose) and the second booster dose (fourth dose) 1 year after the second dose .
- Placebo (Type: PLACEBO_COMPARATOR): 24 participants including 12 at medium dosage stage and 12 at high dosage in phase Ⅰ will receive two doses of placebo according to the immunization schedule of day 0, 28 and will receive 1 dose of booster immunization 1 year after primary immunization; 50 participants in phase Ⅱ will receive two doses of primary immunization according to the immunization schedule of day 0,28 and will receive 1 dose of booster immunization 6 months after primary immunization.
- Experimental Vaccine-low dosage (Type: EXPERIMENTAL): 100 participants at low dosage stage in phase Ⅱ will receive two doses of primary immunization according to the immunization schedule of day 0,28 and will receive 1 dose of booster immunization 6 months after primary immunization.

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

Answer: outcome: complete