Design: Phase 2/3, double-blind, randomised non-inferiority trial
Population: 643 Indian infants aged 6–8 weeks, after birth-dose bOPV
Primary outcome: Type-specific seroconversion 28 days after third dose
Effect: Type 1: 94.7% vs 92.8%; type 2: 96.3% vs 97.9%; type 3: 97.3% vs 99.0%; all non-inferior

This phase 2/3 double-blind trial, published in May 2026 and funded by the Serum Institute of India, randomised 648 infants at nine Indian hospitals to an adjuvanted dose-sparing inactivated polio vaccine (about one quarter of the standard antigen content) or standard IPV at 6, 10 and 14 weeks. All had received birth-dose bivalent OPV.

Seroconversion was non-inferior for all three types: type 1, 94.7% vs 92.8%; type 2, 96.3% vs 97.9%; type 3, 97.3% vs 99.0%. Local reactions and fever were common in both groups; no vaccine-related serious adverse events occurred.

IPV supply and cost have forced fractional dosing in many programmes. A vaccine needing less antigen could make full courses easier to supply. It is not yet in the Universal Immunisation Programme schedule, and regulatory status in India is not stated in the paper.

Continue the current national IPV schedule; the dose-sparing vaccine is not yet a programme product.
Seroconversion with the adjuvanted vaccine was non-inferior for all three poliovirus types.
Fever and local reactions are common with either vaccine; advise parents accordingly.
The trial was industry-funded; independent programme data will follow if it is adopted.

Why it matters

Polio vaccine supply constraints shape programme decisions, and less antigen per dose eases them.

The statistics, in plain English

Non-inferiority means the new vaccine is not worse by more than a set margin (here 10 percentage points). The largest shortfall's confidence interval (type 2, down to −4.7) stayed well inside that margin.