A recent clinical study found that a combination of four probiotic strains (Lactiplantibacillus plantarum KABP-033, L. plantarum KABP-022, L. plantarum KABP-023, and Pediococcus acidilactici KABP-021) can reduce symptom duration in children with viral upper respiratory tract infections (URIs). The findings were consistent with prior research suggesting immune support benefits in adults. The probiotic blend is marketed as AB21 by AB-Biotics and Kaneka Probiotics.

The randomized, placebo-controlled trial recruited 75 children between the ages of 6 months and 5 years with clinically-diagnosed viral upper respiratory tract infections, who either received AB21 or a placebo twice daily for 15 days. The children were monitored at follow-up assessments 15 and 45 days after completing the intervention. The probiotic blend was found to reduce the duration of fever by an average of 1.1 days (40%) compared to placebo, and reduce reported pain and discomfort by 0.7 days (19%) compared to placebo.

This is one of the few pediatric probiotic studies that verified which viruses caused symptoms via both clinical and molecular confirmation, the authors noted. URIs were diagnosed by pediatricians using clear clinical criteria, and PCR analysis of nasopharyngeal swabs. Previous probiotic studies for pediatric URIs relied on parent/caregiver diagnosis, which can be subjective, the authors noted.

Researchers also assessed participants’ body temperature and FLACC (Face, Legs, Activity, Cry, and Consolability) scores, and found that both variables were significantly lower in the probiotic group than in the placebo group. Further, nasal congestion and total number of symptoms were significantly lower in children who received the probiotic blend 15 days after the intervention ended, suggesting that immune-stimulating effects were maintained post-treatment.

“This study expands the evidence that AB21 can positively impact viral respiratory infections through its unique mechanism of action, activating the immune system via its effect on immune cells as well as enhancing the gut barrier function, and reducing local inflammation. Together, the local and systemic effects of AB21 help to accelerate viral clearance, speeding recovery and promoting protection from future infections.”

Though the study allowed the use of over-the-counter medications like ibuprofen to relieve symptoms, the use of these medications was comparable between groups, the authors noted.