Inclusion Criteria:

1. Able and willing to comply with all study requirements.

2. Give informed consent and sign informed consent form (ICF). For subjects who are
unable to read or write, the consent must be witnessed by a literate third party not
involved in the study.

3. BMI in between 18.5 and 30.0 kg/m2 (including upper and lower limits).

4. For each group, meet the following criteria regarding age, COVID-19 vaccination
history (as confirmed by COVID-19 vaccination records), and SARS-CoV-2 infection
history (as confirmed by the investigator according to WHO definitions, Appendix
III):

Group 1: Adult-CoronaVac® group

- Aged 18-59 AND received 2 to 4 homologous doses of CoronaVac® at least 3 months
prior to enrollment AND without SARS-CoV-2 infection history.

Group 2: Adult-Comirnaty® group

- Aged 18-59 AND received 2 to 4 heterologous doses of CoronaVac® and Comirnaty®
at least 3 months prior to enrollment AND without SARS-CoV-2 infection history;
OR

Group 3: Adult-mixed group

- Aged 18-59 AND received 2 to 4 heterologous doses of CoronaVac® and Comirnaty®
at least 3 months prior to enrollment AND without SARS-CoV-2 infection history;
OR

- Aged 18-59 AND received 2 to 4 heterologous doses of CoronaVac® and Comirnaty®
at least 3 months prior to enrollment AND recovered from SARS-CoV-2 infection
at least 3 months prior to enrollment; OR

- Aged 18-59 AND received 2 to 4 homologous doses of CoronaVac® or Comirnaty® at
least 3 months prior to enrollment AND recovered from SARS-CoV-2 infection at
least 3 months prior to enrollment.

Group 4: Elderly-mixed group

- Aged 60-75 AND received 2 to 4 heterologous doses of CoronaVac® and Comirnaty®
at least 3 months prior to enrollment AND without SARS-CoV-2 infection history;
OR

- Aged 60-75 AND received 2 to 4 heterologous doses of CoronaVac® and Comirnaty®
at least 3 months prior to enrollment AND recovered from SARS-CoV-2 infection
at least 3 months prior to enrollment; OR

- Aged 60-75 AND received 2 to 4 homologous doses of CoronaVac® or Comirnaty® at
least 3 months prior to enrollment AND without SARS-CoV-2 infection history; OR

- Aged 60-75 AND received 2 to 4 homologous doses of CoronaVac® or Comirnaty® at
least 3 months prior to enrollment AND recovered from SARS-CoV-2 infection at
least 3 months prior to enrollment.

5. Healthy subjects, or subjects with stable medical condition who have a pre-existing
medical condition that does not meet any exclusion criteria. A stable medical
condition is defined as disease not requiring significant change in therapy or
hospitalization for worsening disease during the 3 months prior to enrollment.

6. Female subjects of childbearing potential with have negative pregnancy test shall be
willing to practice continuous effective contraception and not to breastfeed until
12 months after ICCOV administration.

- Nonchildbearing potential is defined as surgically sterile (history of
bilateral tubal ligation, bilateral oophorectomy, hysterectomy) or
postmenopausal. A follicle-stimulating hormone (FSH) level and the amenorrhea
duration (e.g., amenorrhea for ≥ 12 consecutive months prior to screening
without an alternative medical cause) may be measured at the discretion of the
investigator to confirm postmenopausal status.

- The effective contraceptive methods include sexual abstinence or adequate
contraceptive measures such as intrauterine or implanted contraceptive device,
oral contraceptives, injected or implanted contraceptives, sustained-release
topical contraceptives, condoms (male), diaphragm, and cervical cap, etc.

7. Male subjects who are involved in heterosexual sexual activity must agree to
practice adequate contraception (as described above) and refrain from donating sperm
until 12 months after ICCOV administration.

8. Agreement to avoid blood donation during the study.

Exclusion Criteria:

1. Laboratory confirmed SARS-CoV-2 infection, defined by RT-PCR test.

2. Fever (oral temperature ≥ 37.5°C/axillary temperature ≥ 37.3°C) on the day of
vaccination or within recent 72 hours.

3. Medical history of severe acute respiratory syndrome (SARS), middle east respiratory
syndrome (MERS) within 12 months, and COVID-19 within 3 months prior to enrollment.

4. Abnormal laboratory tests of clinical significance involving hematology, serum
biochemistry, coagulation function, or urinalysis as determined by the investigator.

5. Females who are pregnant or breastfeeding or those who plan to give birth in coming
12 months (including in female subjects or the female partners of male subjects).

6. Participated in other clinical trials and received any other investigational
products within 1 month (or 5 half-lives of the drug, whichever is longer) prior to
enrollment or plan to receive any other investigational products during the study.

7. History of severe allergies to any vaccine or drug, such as urticaria, dyspnea,
edema, abdominal pain and other symptoms after administration, especially
hypersensitivity to the components of ICCOV.

8. Have malignant tumor (except for skin basal cell carcinoma or carcinoma uterine
cervix in situ) and immune disease (e.g., human immunodeficiency virus [HIV]
infection, systemic lupus erythematosus, rheumatoid arthritis, asplenia or
splenectomy, severe combined immunodeficiency disorder [SCID], and other immune
disease that may influence immune response at the investigator's discretion).

9. Have other severe and/or uncontrolled conditions, including but not limited to,
acute infectious disease, cardiovascular disease, respiratory disease,
gastrointestinal disease, liver disease, renal disease, hematology disease,
endocrine disorder, psychiatric condition and neurological illness (e.g.,
Guillain-Barre Syndrome, uncontrolled epilepsy, etc.). Mild/moderate well-controlled
comorbidities are allowed to participate as deemed appropriate by the investigator.

10. Received any investigational or licensed COVID-19 vaccine other than described in
inclusion criteria, or any investigational or approved vaccine against a coronavirus
(including but not limited to SARS-CoV-1 and MERS-CoV) at any time prior to
enrollment.

11. Received any investigational or approved vaccines within 3 months prior to
enrollment or plan to receive any other vaccines during the study.

12. Received any blood products or immunoglobulin products within 3 months prior to
enrollment or plan to receive that during the study.

13. Received interferon, systemic corticosteroids, or other immunosuppressants/
immunomodulators (except for local application) for 14 or more consecutive days
within 6 months prior to enrollment.

14. Medical history or clinical manifestations of any physical or mental illness that
may affect the subject's completion of this study.

15. Needle phobia.

16. Have contraindications for intramuscular administration, such as confirmed
thrombocytopenia, any coagulation dysfunction, or being receiving anticoagulation
therapy.

17. Have contraindications for electroporation, such as implanted with pacemaker,
implanted with Automatic Implantable Cardioverter Defibrillator (AICD), or abnormal
electrocardiogram at screening as determined by the investigator.

18. Any other conditions considered by the investigator as not suitable to participate
in this study.