Read AB21® full scientific paper:

Scientific evidence of AB21®

The first randomized, controlled clinical trial testing a probiotic for the treatment of COVID-19 in mild to moderate patients.

4x blinded, single-center, randomized, placebo-controlled study. 300 patients with mild to moderate COVID-19 symptoms 

Patients were randomized to take orally once a day probiotic AB21 or placebo, for 30 days

AB21 shortened -5 days median symptoms duration (p<0.001). SARS-CoV2 antibodies were significantly increased

Results of this pioneer and innovative publication present AB21 as a solution for a wide range of individuals:


4x blinded

(patient, caregiver, investigator and outcomes assessors)


randomized, placebo-controlled clinical trial

Parallel arms

300 patients

one dose daily

Mild to moderate COVID-19

Almost half of subjects with known metabolic risk factors (diabetes, obesity)
  1. With at least 1 COVID-19 symptom (cough, headache, fever, muscular pain, shortness of breath)
  2. Positive RT-qPCR
  3. Symptom onset less than 7 days before recruitment
  4. No need of oxygen therapy

18 to 60 year-old
(median age of 37)

Study design

Study start
Study end
and random
Placebo group
1 capsule a day, 20 minutes before breakfast
AB21 group
Day 0
Day 1
Day 5
Day 10
Day 15
Day 20
Day 25
Day 30
One site visits
Visit 1
Visit 2
Visit 3
Blood sampling
Swab (RT-qPCR)
Chest X-ray
Phone calls
Call 1
Call 2
Call 3
Call 4
Patient e-diary

Main findings

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AB21 full scientific presentation available only on demand

Remission rate twice as high in probiotic than placebo


Remission was defined as disappearance of symptoms and negative RT-qPCR. As primary study outcome, remission rate on day 30 was 53·1% (78 of 147) in the active group compared to 28·1% (41 of 146) in the placebo group (p<0·0001)

Faster symptomatic recovery by 5 days in the probiotic group compared to placebo

-5 days

Probiotic group had a median symptoms duration of 13 days, while in the placebo group it was 18 days. Probiotic effect on symptoms was robust to baseline imbalances

Shortening of the duration of individual symptoms including fever, cough and headache. Paracetamol use also reduced

-2 to -5 days

Average duration of individual symptoms was significantly reduced in probiotic compared to placebo (ranging from p < 0.05 to p <0.001)

IgG antibodies against SARS-CoV2 in probiotic group twice as high as in placebo


Higher increase of SARS-CoV2-specific IgG in serum (p < 0·0001). Differences significant both on day 15 and day 30.

Higher counts of IgM antibodies against SARS-CoV2 in probiotic group

Higher increase of SARS-CoV2-specific IgM in serum (p < 0·0001). Differences significant both on day 15 and day 30.

Improvement of lung abnormalities contributing to respiratory health

Lung abnormalities were monitored via X-ray. Probiotic reduced overall scoring on days 15 and 30 vs placebo (both p < 0.001)

Less viral load in nasal secretions, diminishing risk of virus transmission

Significant reduction of viral load by probiotic compared to placebo (p < 0.001).

Evaluated in nasopharyngeal swabs

Increased Interferon-Beta serum levels, an anti-inflammatory cytokine

A post-hoc analysis identified an effect on Beta-Interferon levels, with a significant increase vs placebo on days 15 and 30 (p<0.001)

Interested in knowing more?

Recently, AB21® clinical trial results where presented at the 8th IHMC Congress. Fulfill the form below and you will recieve the recorded session. Only available for industry members and healthcare professionals.