Efficacy and Safety of Oral Lactobacillus Plantarum GUANKE (CGMCC NO.21720) in Enhancement of Antibody Level After SARS-CoV-2 Vaccination (Trial 2)

Efficacy and Safety of Oral Lactobacillus Plantarum GUANKE (CGMCC NO.21720) in Enhancement of Antibody Level After SARS-CoV-2 Vaccination: A Prospective, Randomized, Double-blind, Placebo-Controlled Trial (Trial 2)

Preliminarily explore the effect of oral probiotics in SARS-CoV-2 serum neutralizing antibody titer level and T cell response level (spot formation cell counting).

Provide a reference for determining the appropriate oral regimen. Provide necessary parameters for estimating the sample size of confirmatory clinical trial.

In selected communities or assigned clinical trial institutions, participants who intend to complete the third dose of SARS-CoV-2 vaccination will be invited in this study. Informed consent form will give to potential participants with well explained of trial contents during baseline. Participants who gave their signed informed consent form will be blocked randomized in a 1:1:1:1 ratio to intervention group A, intervention group B, intervention group C, or placebo group D.

Inclusion Criteria:

1. 18 ≤age ≤59 years;
2. Vaccinated with two doses of SARS-CoV-2 vaccine (manufactured by Sino Biopharmaceutical Limited or SINOVAC BIOTECH CO., LTD.) (≥6 months from the time of vaccination).
3. Plan to vaccinate third dose vaccination (manufactured by Sino Biopharmaceutical Limited or SINOVAC BIOTECH CO., LTD.);
4. Voluntarily participate in the study with signed informed consent form.

Exclusion criteria:

1. Pregnancy or lactation period;
2. Infected with human immunodeficiency virus (HIV), hepatitis B virus (HBV) or hepatitis C virus (HCV);
3. History of autoimmune diseases (e.g. rheumatoid arthritis, systemic lupus erythematosus, dry syndrome, etc.);
4. Previously infected with SARS-CoV-2 or close contact of SARS-CoV-2 infected individual;
5. Other SARS-CoV-2 vaccination history (not manufactured by Sino Biopharmaceutical Limited or SINOVAC BIOTECH CO., LTD.);
6. End-stage cancer or other terminal diseases with life expectancy <6 month;
7. History of severe cardiovascular and cerebrovascular diseases, such as heart failure, uncontrolled coronary heart disease, cardiomyopathy, uncontrolled arrhythmia, or history of myocardial or cerebral infarction within past six months;
8. Participating in other clinical trials.