*1.Age >= 18 years old and < 60 years old, regardless of gender (for adult subjects only), 2.Age >= 60 years old and <= 85 years old, regardless of gender (for elderly subjects), 3.Body mass index (BMI) is between 18-35 kg/m2 (including upper and lower limits), 4.Axillary temperature < 37.3 degrees C on the day of vaccination. 5.Subjects are considered by the investigator as healthy subjects eligible for immunization with this product based on inquiry of medical history and inspection of the physical examination results. 6.Subjects volunteer to participate in this clinical trial, and are able to correctly understand and sign the Informed Consent Form (ICF), 7.Subjects can cooperate with the investigator, observe the requirements of the protocol, and complete the examinations according to relevant procedures in the protocol, agree to abide by the modes of life stipulated in the protocol (restrictions on going abroad, business trips or travel) during the study period.

*1.Age >= 18 years old and < 60 years old, regardless of gender (for adult subjects only), 2.Age >= 60 years old and <= 85 years old, regardless of gender (for elderly subjects), 3.Body mass index (BMI) is between 18-35 kg/m2 (including upper and lower limits), 4.Axillary temperature < 37.3 degrees C on the day of vaccination. 5.Subjects are considered by the investigator as healthy subjects eligible for immunization with this product based on inquiry of medical history and inspection of the physical examination results. 6.Subjects volunteer to participate in this clinical trial, and are able to correctly understand and sign the Informed Consent Form (ICF), 7.Subjects can cooperate with the investigator, observe the requirements of the protocol, and complete the examinations according to relevant procedures in the protocol, agree to abide by the modes of life stipulated in the protocol (restrictions on going abroad, business trips or travel) during the study period.

The first segment: The subjects eligible for this study must meet all of the following inclusion criteria: 1.Age >= 18 years old and < 60 years old, regardless of gender. 2.Age >= 60 years old and <= 85 years old, regardless of gender. 3.Body mass index (BMI) is between 18-35 kg/m2 (including upper and lower limits), 4.Axillary temperature < 37.3 degrees C on the day of vaccination. 5.Subjects are considered by the investigator as healthy subjects eligible for immunization with this product based on inquiry of medical history and inspection of the physical examination results. 6.Subjects volunteer to participate in this clinical trial, and are able to correctly understand and sign the Informed Consent Form (ICF), 7.Subjects can cooperate with the investigator, observe the requirements of the protocol, and complete the examinations according to relevant procedures in the protocol, agree to abide by the modes of life stipulated in the protocol (restrictions on going abroad, business trips or travel) during the study period. The second segment: 1.Subjects aged >= 18 years, regardless of sex, who have received two doses of COVID-19 DNA vaccine within 6-12 months before participating in the study screening of this stage (for the second segment). 2.Body mass index (BMI) is between 18-35 kg/m2 (including upper and lower limits), 3.Axillary temperature < 37.3 degrees C on the day of vaccination. 4.Subjects are considered by the investigator as healthy subjects eligible for vaccination with this product based on the inquiry of medical history and inspection of the physical examination results. 5.Subjects who volunteer to participate in this clinical trial should be able to correctly understand and sign the Informed Consent Form (ICF), 6.Subjects can cooperate with the investigator, observe the requirements of the protocol, and complete the examinations according to relevant procedures in the protocol, agree to abide by the modes of life stipulated in the protocol (restrictions on going abroad, business trips or travel) during the study period.

The first segment: The subjects eligible for this study must meet all of the following inclusion criteria: 1.Age >= 18 years old and < 60 years old, regardless of gender. 2.Age >= 60 years old and <= 85 years old, regardless of gender. 3.Body mass index (BMI) is between 18-35 kg/m2 (including upper and lower limits), 4.Axillary temperature < 37.3 degrees C on the day of vaccination. 5.Subjects are considered by the investigator as healthy subjects eligible for immunization with this product based on inquiry of medical history and inspection of the physical examination results. 6.Subjects volunteer to participate in this clinical trial, and are able to correctly understand and sign the Informed Consent Form (ICF), 7.Subjects can cooperate with the investigator, observe the requirements of the protocol, and complete the examinations according to relevant procedures in the protocol, agree to abide by the modes of life stipulated in the protocol (restrictions on going abroad, business trips or travel) during the study period. The second segment: 1.Subjects aged >= 18 years, regardless of sex, who have received two doses of COVID-19 DNA vaccine within 6-12 months before participating in the study screening of this stage (for the second segment). 2.Body mass index (BMI) is between 18-35 kg/m2 (including upper and lower limits), 3.Axillary temperature < 37.3 degrees C on the day of vaccination. 4.Subjects are considered by the investigator as healthy subjects eligible for vaccination with this product based on the inquiry of medical history and inspection of the physical examination results. 5.Subjects who volunteer to participate in this clinical trial should be able to correctly understand and sign the Informed Consent Form (ICF), 6.Subjects can cooperate with the investigator, observe the requirements of the protocol, and complete the examinations according to relevant procedures in the protocol, agree to abide by the modes of life stipulated in the protocol (restrictions on going abroad, business trips or travel) during the study period.

1. Aged 18 to 60 years old, male or female (for adult subjects only), 2. Aged 60 to 85 years old, male or female (for elderly subjects only), 3. Body mass index (BMI) of 18-35 kg/m2 (inclusive), 4. Axillary temperature < 37.3 degrees C on the day of vaccination, 5. Subjects are considered by the investigator as healthy subjects eligible for immunization with this product based on inquiry of medical history and inspection of the physical examination results, 6. Subjects volunteer to participate in this clinical trial, and are able to correctly understand and sign the written Informed Consent Form (ICF), 7. Subjects can cooperate with the investigator, observe the requirements of the protocol, and complete the examinations according to relevant procedures in the protocol, agree to abide by the mode of life stipulated in the protocol (restrictions on overseas trips, business trips or travel) during the study period.

1. Aged 18 to 60 years old, male or female (for adult subjects only), 2. Aged 60 to 85 years old, male or female (for elderly subjects only), 3. Body mass index (BMI) of 18-35 kg/m2 (inclusive), 4. Axillary temperature < 37.3 degrees C on the day of vaccination, 5. Subjects are considered by the investigator as healthy subjects eligible for immunization with this product based on inquiry of medical history and inspection of the physical examination results, 6. Subjects volunteer to participate in this clinical trial, and are able to correctly understand and sign the written Informed Consent Form (ICF), 7. Subjects can cooperate with the investigator, observe the requirements of the protocol, and complete the examinations according to relevant procedures in the protocol, agree to abide by the mode of life stipulated in the protocol (restrictions on overseas trips, business trips or travel) during the study period.

1. Aged 18 to 60 years old, male or female (for adult subjects only), 2. Aged 60 to 85 years old, male or female (for elderly subjects only), 3. Body mass index (BMI) of 18-35 kg/m2 (inclusive), 4. Axillary temperature < 37.3 degree C on the day of vaccination, 5. Subjects are considered by the investigator as healthy subjects eligible for immunization with this product based on inquiry of medical history and inspection of the physical examination results, 6. Subjects volunteer to participate in this clinical trial, and are able to correctly understand and sign the written Informed Consent Form (ICF), 7. Subjects can cooperate with the investigator, observe the requirements of the protocol, and complete the examinations according to relevant procedures in the protocol, agree to abide by the mode of life stipulated in the protocol (restrictions on overseas trips, business trips or travel) during the study period.

1. Aged 18 to 60 years old, male or female (for adult subjects only), 2. Aged 60 to 85 years old, male or female (for elderly subjects only), 3. Body mass index (BMI) of 18-35 kg/m2 (inclusive), 4. Axillary temperature < 37.3 degree C on the day of vaccination, 5. Subjects are considered by the investigator as healthy subjects eligible for immunization with this product based on inquiry of medical history and inspection of the physical examination results, 6. Subjects volunteer to participate in this clinical trial, and are able to correctly understand and sign the written Informed Consent Form (ICF), 7. Subjects can cooperate with the investigator, observe the requirements of the protocol, and complete the examinations according to relevant procedures in the protocol, agree to abide by the mode of life stipulated in the protocol (restrictions on overseas trips, business trips or travel) during the study period.