Please assess the completion status of the following clinical trial:

Trial Title: Efficacy and Safety of Heterologous and Homologous COVID-19 Vaccination

Study Design Characteristics:
- Allocation: NON_RANDOMIZED
- Intervention Model: PARALLEL
- Observational Model: None
- Primary Purpose: PREVENTION
- Time Perspective: None
- Masking: NONE
- Phase: None
- Number of Arms: 5.0

Eligibility Criteria:
Inclusion Criteria:~1. Males or females aged ≥20 to \<65 years old and have received adenovirus vector vaccine ChAdOx1-nCov-19 (Astra-Zeneca) or SARS-CoV-2 messenger RNA-1273 once within three months at least four weeks apart.~2. The subject must sign the subject's inform consent, or the subject's legal representative must understand and agree, then sign inform consent according to procedure above.~3. Healthy or existing medical condition is stable, and within 3 months before being included in the trial, he or she has not been hospitalized due to illness, and his or her condition is expected to remain stable during the trial period.~Exclusion Criteria:~1. Are currently pregnant or breastfeeding or plan to become pregnant within 30 days after the second dose of the trial vaccine.~2. Currently receiving or receiving other vaccines, including Streptococcus pneumoniae vaccine.~3. Have used any blood products or intravenous immunoglobulin within 12 weeks before entering the test. Receive concurrent immunosuppressive or immunomodulatory therapy (including steroid prednisone, targeted drugs such as infliximab, adalimumab, etanercept) within 12 weeks.~4. Immunosuppressive diseases or immune insufficiency states, including hematological malignancies, parenchymal organs, bone marrow transplant history or asplenia, autoimmune diseases (systemic lupus, rheumatoid arthritis, scleroderma, polyarthritis, autoimmune thyroiditis, etc.) and human immunodeficiency virus infection.~5. Bleeding disease and assessed as a contraindication to prohibit the use of intramuscular injection or blood draw.~6. Other condition, such as physical examination or instability according to the trial investigator's judgment, or participation in this trial may adversely affect the safety of subjects, fail to comply with trial regulations, or interfere with trial evaluation indicators.~7. The subject is known to have been infected with severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2).

- Gender: ALL
- Minimum Age: 20 Years
- Maximum Age: 65 Years
- Healthy Volunteers: t

Study Arms:
- Heterologous ChAdOx1-nCov-19 vaccination - 8 weeks apart (Type: ACTIVE_COMPARATOR): Astra-Zeneca vaccine 0.5 mL/dose
- mRNA-1273 Vaccination and Heterologous ChAdOx1-nCov-19 vaccination- 8 weeks apart (Type: ACTIVE_COMPARATOR): Moderna COVID-19 Vaccine 0.5 mL/dose and Astra-Zeneca vaccine 0.5 mL/dose
- Heterologous ChAdOx1-nCov-19 vaccination and the mRNA-1273 Vaccination- 4 weeks apart (Type: ACTIVE_COMPARATOR): Moderna COVID-19 Vaccine 0.5 mL/dose and Astra-Zeneca vaccine 0.5 mL/dose
- The mRNA-1273 Vaccination- 4 weeks apart (Type: ACTIVE_COMPARATOR): Moderna COVID-19 Vaccine 0.5 mL/dose
- Heterologous ChAdOx1-nCov-19 vaccination and the mRNA-1273 Vaccination-12 weeks apart (Type: ACTIVE_COMPARATOR): Moderna COVID-19 Vaccine 0.5 mL/dose and Astra-Zeneca vaccine 0.5 mL/dose

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

Answer: outcome: complete