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Repeat BCG vaccination

Academic research (Massachusetts General Hospital and other investigators at other sites)

What it is

Repeated BCG vaccination remains an experimental immune/metabolic approach to T1D. A June 2026 adult phase 2 conference abstract reports a five-year juvenile-onset adult subgroup, but gives within-treatment changes without a placebo effect estimate. Small long-term and pediatric reports do not establish insulin independence or a proven clinical benefit.

Editorial review: .

Most recent recorded citation date: 2026-06-18. Only explicit date metadata is included; an undated citation may be newer. This does not mean every claim was reviewed on that date.

Trial status, labels and access can change between reviews. How we review the evidence · How to read the evidence

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Years awayEarly evidencebcgimmunotherapyvaccinerepurposedmetabolic

Evidence behind this assessment

Key evidence notes. Study results, product eligibility and access answer different questions.

Who was studied?
Study populations and analysis groups vary. Product age limits alone do not describe who was studied.See the linked studies and their populations →
Benefit or performance
Beta-cell preservation: The 2018 long-term study reported no clinically meaningful C-peptide restoration. Its metabolic hypothesis should not be interpreted as established beta-cell regeneration.[3]
Important harms and treatment burden
Safety: BCG is used for tuberculosis prevention, but CDC guidance lists immunosuppression and pregnancy as contraindications. Historical vaccine experience does not establish the safety of repeated T1D treatment.[10]
Approval and country access
Country-specific approval and access are not summarized in this record.Approval, trial recruitment, local supply and funding are separate. Check the cited label or access source.
Follow-up and remaining uncertainty
Durability: The reported eight-year HbA1c signal came from only three BCG-treated and three placebo participants in the original randomized cohort. Durability beyond that small cohort remains uncertain.[3]

Research status alone does not establish approval, clinical benefit or local availability. This record cites company or conference reports. Those sources may describe interim findings; their source type is shown in the source list.

Editorial score: calculation and evidence

A weighted editorial judgment on a 0–100 scale, not a probability of success or a measured treatment effect. Higher criterion scores mean more favorable assessments.

Score limitations. Scores remain editorial judgments, not measured probabilities of beta-cell recovery, durable benefit or safety. Evidence spans different BCG strains, regimens, disease durations and reporting levels; the new conference subgroup has no reported between-arm outcome estimate.

Default calculation: 20 × 30 + 35 × 20 + 65 × 20 + 45 × 10 + 35 × 20 = 3750; divide by total weight 100. Unrounded weighted result: 37.5.

Beta-cell preservation20

The 2018 long-term study reported no clinically meaningful C-peptide restoration. Its metabolic hypothesis should not be interpreted as established beta-cell regeneration.[3]

Durability35

The reported eight-year HbA1c signal came from only three BCG-treated and three placebo participants in the original randomized cohort. Durability beyond that small cohort remains uncertain.[3]

Safety65

BCG is used for tuberculosis prevention, but CDC guidance lists immunosuppression and pregnancy as contraindications. Historical vaccine experience does not establish the safety of repeated T1D treatment.[10]

Eligibility breadth45

The current US pediatric study includes established T1D from age 8 to under 18, with listed medical exclusions. This is trial eligibility, not an approved treatment population.[2]

Maturity35

The adult study remains phase 2 and active, not recruiting, with estimated enrollment of 150 and estimated July 2029 primary completion. An earlier conference subgroup report does not complete the trial or establish approval.[1]

The full picture

Repeat BCG vaccination is being investigated as an immune/metabolic treatment for established type 1 diabetes. BCG is a tuberculosis vaccine; its licensed vaccine indication does not establish a T1D treatment indication. The studies reviewed here do not establish durable insulin independence or clinically meaningful restoration of beta-cell function.1135

Small long-term studies: a signal, not a large efficacy trial

The original 2012 randomized, placebo-controlled study enrolled six adults, three per group, and monitored them for 20 weeks. It reported transient immune and very-low-level C-peptide changes, with no significant HbA1c change. One placebo participant developed Epstein–Barr virus infection and also showed immune/C-peptide changes, complicating interpretation of these exploratory biomarkers.4

The 2018 follow-up reported delayed HbA1c lowering beginning around year 3 and continuing through year 8 in the three BCG recipients, compared with the three placebo recipients. Mean HbA1c reached 6.65% in the treated group at year 8. Other shorter-followed clinical groups and laboratory participants increased the paper's total research population, but do not enlarge that six-person randomized eight-year comparison. The authors found no clinically meaningful return of C-peptide and proposed altered glucose metabolism rather than pancreatic regeneration as the explanation. Their mechanistic findings do not establish a broadly reproducible clinical effect.3

An actual phase 2 conference report now exists

The ADA 2026 conference abstract 2862-LB, dated 5 June 2026, reports a juvenile-onset adult subgroup from NCT02081326: 34 BCG and 24 placebo participants followed for five years. It reports mean HbA1c in the BCG group changing from 7.84% to 7.30% and insulin use from 0.68 to 0.63 units/kg/day. These are reported within-BCG-group changes, not a placebo-adjusted treatment effect: the abstract does not provide corresponding placebo outcome values or a between-arm estimate. C-peptide did not improve.5

The abstract's “normoglycemia” outcome uses 70–99 mg/dL (3.9–5.5 mmol/L), not the usual 70–180 mg/dL (3.9–10.0 mmol/L) time-in-range definition. It describes safety favourably in the abstract but supplies no detailed adverse-event table or denominators for the CGM outcomes. A full report is needed to assess missing data, subgroup selection, comparisons and harms. These are primary conference findings, with limited information for assessing clinical benefit.5

Negative trials and mixed evidence

A 1999 randomized study assigned 94 children aged 5 to 18 with recent-onset T1D, 47 per arm, to BCG or saline. The original abstract reports no differences in remission, C-peptide, insulin requirements or HbA1c; 16 noncompleters were excluded from the analysis. This single-dose, recent-onset study differs from later repeated-dose, established-T1D regimens, so it should neither be ignored nor treated as an exact test of those regimens.6

A 2020 systematic review included four studies and 198 participants. Its reported HbA1c meta-analysis used three studies and 148 participants, finding no statistically significant difference: −0.12 percentage points (95% CI −0.53 to 0.30). Regimen, population and follow-up differences limit that pooled estimate. A newer review's original abstract, published online 18 June 2026, also describes heterogeneous and conflicting evidence. Its search ended in May 2026, so it does not resolve the later ADA report; the full subscription review was not available in this audit.78

Separate pediatric study in Iran

The Iranian Yazd study reported 33 children randomized and 32 analyzed after two BCG doses or placebo. Its table shows BCG-group HbA1c of 9.49% at baseline and 8.87% at 18 months, but supplies no 18-month control value; the figure prints a different 18-month value. This does not establish an 18-month between-group benefit. C-peptide testing was restricted to the BCG group and did not change significantly. Reported absence of local/systemic adverse effects in this small study is not proof of an absence of uncommon harms.9

Current trial status and practical limits

The current US adult and pediatric registry records both say active, not recruiting and each lists estimated enrollment of 150, not a confirmed final analysis sample. Estimated primary completion is July 2029 for adults and March 2031 for children. These are planning dates, not promised publication dates or evidence that no earlier outcomes exist. The adult record includes juvenile-onset T1D and an exploratory LADA (latent autoimmune diabetes in adults) population; the pediatric study's current entry is ages 8 to under 18 with established disease and medical exclusions.12

BCG's use as a vaccine does not make repeated T1D treatment risk-free. CDC advises against BCG in immunosuppressed people and pregnancy, and the T1D trials list infection and other exclusions. The reports do not establish that BCG can replace insulin treatment. Trial status is not an invitation to self-administer a tuberculosis vaccine for diabetes.1013

Coming soon

ETA · No established T1D approval timeline. Registry primary-completion estimates are July 2029 for the US adult study and March 2031 for the pediatric study; an adult subgroup was already reported in an ADA 2026 conference abstract.

Sources

  1. [1]
    Repeat BCG vaccinations for established type 1 diabetes (NCT02081326) · Trial registry — Current API last update posted 13 April 2026. Active, not recruiting; estimated enrollment of 150 and July 2029 primary completion. No structured registry results; separate conference outcomes exist.
  2. [2]
    Repeat BCG vaccinations for pediatric type 1 diabetes (NCT05180591) · Trial registry — Current API last update posted 26 June 2026. Active, not recruiting; estimated enrollment of 150 and March 2031 primary completion.
  3. [3]
    Long-term reduction in hyperglycemia in advanced type 1 diabetes: the value of induced aerobic glycolysis with BCG vaccinations · Peer-reviewed study · 2018-06-21 — Eight-year follow-up of the original six randomized participants (three BCG/three placebo), with additional shorter-followed and mechanistic cohorts. These are not a large randomized efficacy sample.
  4. [4]
    Proof-of-Concept, Randomized, Controlled Clinical Trial of Bacillus-Calmette-Guerin for Treatment of Long-Term Type 1 Diabetes · Peer-reviewed study · 2012-08-08 — Original 20-week randomized study: six participants; transient biomarker findings, no significant HbA1c change.
  5. [5]
    2862-LB: Phase II Clinical Trial of BCG Immunotherapy for Type 1 Diabetes with Juvenile Onset: Five-Year Analysis of Safety, HbA1c, Time in Range, and Insulin Use · Conference finding · 2026-06-05 — Original published ADA conference abstract and publisher-deposited abstract checked. Juvenile-onset adult subgroup: 34 BCG and 24 placebo. Reported outcomes are within-BCG changes, without placebo values or a between-arm effect estimate.
  6. [6]
    Effect of Bacillus Calmette-Guerin vaccination on new-onset type 1 diabetes. A randomized clinical study · Peer-reviewed study — 1999 original abstract checked: 94 children aged 5 to 18 randomized, 47 per arm, with 16 noncompleters excluded from analysis. No remission, C-peptide, insulin-dose or HbA1c advantage. Full report not retrieved in this review.
  7. [7]
    Therapeutic Effects of BCG Vaccination on Type 1 Diabetes Mellitus: A Systematic Review and Meta-Analysis of Randomized Controlled Trials · Peer-reviewed study — Original review full text checked. Four studies and 198 participants overall; HbA1c meta-analysis uses three studies and 148 participants. Regimens, populations and follow-up differ.
  8. [8]
    BCG vaccination as an adjunctive strategy in type 1 diabetes: A systematic review of immunometabolic effects and clinical evidence · Peer-reviewed study · 2026-06-18 — Original abstract and publication metadata checked, not subscription full text. Search through May 2026; heterogeneous intervention and observational evidence. October 2026 is the issue date, not online publication date.
  9. [9]
    Bacillus Calmette-Guerin in controlling type 1 diabetes: A quasi-experimental randomized clinical trial · Peer-reviewed study · 2026-03-10 — Separate Iranian pediatric study: 33 randomized and 32 analyzed; missing 18-month control HbA1c and conflicting table/figure values limit interpretation. Registry status not independently confirmed.
  10. [10]
  11. [11]
    FDA — BCG vaccine licensed indication · Regulatory decision — The listed vaccine indication is tuberculosis prevention, not treatment of type 1 diabetes; this is not the specific investigational Tokyo-strain trial product.