Inclusion Criteria:

1. The subjects are healthy individuals aged between 18 and 65 years old (inclusive),
with no gender preference, ensuring an appropriate gender ratio.

2. Have received 2-3 doses of COVID-19 inactivated vaccine, and the last dose was
administered more than 6 months ago.

3. Have not been infected with COVID-19 within 3 months.

4. Capable of being used in conjunction with nasal sprays, and also suitable for nasal
irrigation, saliva collection, and blood collection.

5. Male subjects and their partners, or female subjects, must agree to adopt one or
more non-drug contraceptive measures (such as complete abstinence, condoms,
intrauterine devices, partner sterilization, etc.) during the trial period and for
six months after the trial ends, and they must not have plans for sperm donation or
egg donation.

6. The subjects fully understand the purpose, nature, methods, and possible adverse
reactions of the trial, voluntarily participate in the trial, and sign the informed
consent form.

7. The subject is able to communicate effectively with the researcher and complete the
study in accordance with the protocol.

Exclusion Criteria:

1. Active or suspected viral, bacterial, fungal, or parasitic infections, including
herpes, shingles, or cold sores, within 14 days prior to screening.

2. History of recurrent infections of unknown causes; or use of systemic antibiotics
within 90 days prior to drug administration.

3. Individuals with malignant tumors or a history of malignant tumors, except for
non-melanoma skin cancer that has been cured for more than 3 years.

4. Nasal malformation, trauma, or other reasons that make it impossible to use nasal
sprays.

5. Individuals with a history of allergy to biological agents or any drug components;
individuals with a history of allergies, such as asthma, aspergillus infection,
allergic rhinitis, etc., who have been determined by researchers to be unsuitable
for enrollment.

6. Screen for outpatient or inpatient history of clinically significant chronic or
acute disease symptoms within the previous 3 months, and ensure no surgical plans
during the study period.

7. Previous tests have found HIV-Ab positive, HCV positive, and anti-syphilis
helical-specific antibody positive (please consult the subject).

8. Individuals with abnormal vital signs (refer to normal range: systolic blood
pressure 90~139mmHg, diastolic blood pressure 60~89mmHg, pulse rate 55-100
beats/min; body temperature (ear temperature) 35.4-37.7℃; respiratory rate 16-20
breaths/min) or abnormal electrocardiogram (QTcB≥450 ms, QTcB= QT/RR0.5) or
clinically significant abnormalities in physical examination, laboratory tests
(subject to the judgment of the clinical research doctor).

9. Screen for the use of other medications, including prescription or non-prescription
drugs, and herbal remedies, within the previous 4 weeks.

10. Screen for individuals who have received vaccination within the previous 4 weeks or
plan to receive vaccination during the study period.

11. Individuals with a history of significant allergic reactions (anaphylaxis or
angioedema) to any products (such as food and drugs), and known to be allergic to
the test drug, its excipients, or similar drugs.

12. Participate in any other drug clinical trials within 3 months before screening or
within 5 half-lives of other clinical trial drugs (choose the longer time period).

13. Exclude individuals who have donated plasma or whole blood exceeding 200 mL within
the previous 3 months, except during menstruation.

14. Individuals who abuse drugs or have used soft drugs (such as marijuana) within the
past 3 months, or have consumed hard drugs (such as cocaine, phencyclidine, etc.)
within the year prior to the trial; or individuals who test positive for drug abuse
in urine screening (including methamphetamine, ketamine, MDMA, marijuana, morphine).

15. Individuals who are alcoholics or have regularly consumed alcohol within the 6
months prior to the trial, with an average weekly alcohol intake exceeding 14 units
(1 unit of alcohol is equivalent to approximately 360 mL of beer, 45 mL of spirits
with a 40% alcohol content, or 150 mL of wine), or those who cannot abstain from
alcohol during the trial period (interview).

16. Subjects who have smoked an average of more than 5 cigarettes per day or used other
nicotine-containing products (such as nicotine patches, nicotine gum, e-cigarettes,
etc.) more than 5 times per day on average within the previous 3 months, or who
cannot stop using any tobacco-related products during the trial period.

17. Those who have previously or currently suffered from any clinically severe diseases
of the circulatory system, endocrine system, nervous system, digestive system,
respiratory system, urogenital system, hematology, immunology, psychiatry, or
metabolic abnormalities, or any other diseases that may interfere with the results
of the trial.

18. Use other medications, including prescription or non-prescription drugs, and Chinese
herbal medicine, from the screening date to D1.

19. Women who are pregnant, breastfeeding, or may become pregnant.

20. Clinical diagnosis of any autoimmune disease or rheumatic disease.

21. The patient's blood COVID-19 specific IgG antibody is greater than 1×10e4.

22. Any situation that other researchers consider unsuitable for participation in the
study.

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