Abstract
BACKGROUND: Vaccination is the most effective way to prevent coronavirus disease 2019 (COVID-19). However, it is often less protective and does not significantly increase antibody levels, especially in individuals with impaired immune systems. Nevertheless, the immunocompetence can be enhanced using a natural immunomodulator, such as Dendrobium officinale aqueous extract (DoAE). METHODS: To determine whether DoAE promotes antibody production, we treated healthy volunteers with DoAE during COVID-19 vaccination. Meanwhile, the control volunteers were given a placebo (cornstarch) during the vaccination. Antibody levels were measured at three-week intervals in the DoAE and control groups. RESULTS: DoAE enhanced immunity and preserved immune cell homeostasis. However, the neutralizing antibody (nAb) levels in the DoAE group were lower than those in the control group. Analysis of the gut microbiota revealed that the abundance of anti-inflammatory flora was increased, while the pro-inflammatory flora was reduced in the DoAE group. CONCLUSION: DoAE has immunomodulatory and anti-inflammatory properties. Therefore, DoAE has the potential for COVID-19 prophylaxis, treatment, and recovery from the adverse effects of COVID-19. However, its anti-inflammatory activity affects the production of nAbs. Thus, DoAE may not be recommended for consumption during COVID-19 vaccination.