Effects of Loigolactobacillus coryniformis K8 CECT 5711 on the Immune Response of Elderly Subjects to COVID-19 Vaccination: A Randomized Controlled Trial

Abstract

Elderly people are particularly vulnerable to COVID-19, with a high risk of developing severe disease and a reduced immune response to the COVID-19 vaccine. A randomized, placebo-controlled, double-blind trial to assess the effect of the consumption of the probiotic Loigolactobacillus coryniformis K8 CECT 5711 on the immune response generated by the COVID-19 vaccine in an elderly population was performed. Two hundred nursing home residents >60 yrs that had not COVID-19 were randomized to receive L. coryniformis K8 or a placebo daily for 3 months. All volunteers received a complete vaccination schedule of a mRNA vaccine, starting the intervention ten days after the first dose. Specific IgG and IgA antibody levels were analyzed 56 days after the end of the immunization process. No differences between the groups were observed in the antibody levels. During the intervention, 19 subjects had COVID-19 (11 receiving K8 vs. 8 receiving placebo, p = 0.457). Subgroup analysis in these patients showed that levels of IgG were significantly higher in those receiving K8 compared to placebo (p = 0.038). Among subjects >85 yrs that did not get COVID-19, administration of K8 tended to increase the IgA levels (p = 0.082). The administration of K8 may enhance the specific immune response against COVID-19 and may improve the COVID-19 vaccine-specific responses in elderly populations.

Keywords: COVID-19; elderly; immune response; probiotic.

Figure 1

Flow chart of the study.

Figure 2

Levels of SARS-CoV-2 S1 RBD IgG and IgA antibodies (represented in Log10 of U/mL) in (A) volunteers infected with SARS-COV-2 during intervention (n = 10 in the probiotic group, n = 6 in the control group) and (B) volunteers not infected with SARS-CoV-2 older than 85 years old (n = 40 in the probiotic group, n = 48 in the control group). Data are represented as mean (bars) and SE (vertical lines). p value indicated differences between probiotic group (dark grey bars) and control (light grey bars) groups (univariate models adjusted by age, sex, disease index, and time to Covid-19 symptom’s resolution in Covid-19-infected subjects and adjusted by sex, disease index, and glucocorticoids in uninfected subjects).

Figure 3

Relationship between the levels of SARS-CoV-2 S1 RBD IgA (represented in Log10 of U/mL) and levels of TGF-β (represented in Log10 of pg/mL) by control group (light grey points) and probiotic group (dark grey points). p values indicated the statistical significance of the linear regression analysis by intervention group adjusted by age, sex, and disease index.