Our Take
The adjuvant works in rats but requires booster injections and has not yet been tested in larger animals or humans; the claim that it reproduces oral vaccine immunity is premature.
Why it matters
Polio eradication stalled partly because injectable vaccines don't block transmission as well as oral ones, yet some countries abandoned oral vaccines due to rare infection risk. A safe injectable that stops shedding would remove that trade-off for vaccination campaigns.
Do this week
Vaccine program leads: track publication of large-animal efficacy data (expected within 12 months per the team's stated timeline) before considering pivot away from current polio vaccine strategies.
MIT Researchers Pair Vitamin A Derivative With Nanoparticles to Reach the Gut
An MIT-led team, including collaborators at Harvard Medical School, designed an injectable polio vaccine augmented with Am80, a vitamin A derivative, encapsulated in lipid nanoparticles (LNPs). The nanoparticles release the adjuvant slowly over days, eliminating the need for repeated injections that would be impractical in field campaigns.
In rat studies, the team injected the standard inactivated polio vaccine alongside the Am80-LNP adjuvant, with boosters at four and eight weeks. The nanoparticles accumulated in lymph nodes, where they triggered B and T cells to produce surface proteins that direct immune cells to the gastrointestinal tract. The result: a two-fold increase in IgA antibodies, which coat mucosal membranes and block infection at the point of entry. The rats also produced normal IgG antibodies in the bloodstream, matching the standard injectable response (per the Science Advances paper).
"By adding Am80 to lipid nanoparticle as an adjuvant, we are combining the safety of IPV [inactivated polio vaccine] with an adjuvant that can produce the mucosal immunity that normally you can only get with OPV [oral polio vaccine]," said Behnaz Eshaghi, lead author and postdoctoral researcher at MIT.
Closing the Transmission Gap Without Oral Vaccine Risk
The injectable polio vaccine prevents illness but does not reliably block virus shedding in the gastrointestinal tract, where poliovirus is first encountered and transmitted via contaminated food or water. The oral vaccine induces mucosal immunity and blocks that transmission more effectively. However, several countries stopped using the oral vaccine because it carries a small but real risk of vaccine-derived infection.
An injectable that triggers mucosal immunity would allow vaccination campaigns to preserve transmission control without that safety liability. For polio eradication efforts, which have reduced cases from thousands annually in the 1980s to near-zero today, closing the final shedding pathway is critical. Asymptomatic vaccinated individuals can still spread virus, a fact that complicates eradication in areas with low vaccination rates or high population density.
The team plans next to test the vaccine and adjuvant mixed together in larger animal models. Humans trials remain years away. Am80 and similar formulations could also apply to vaccines targeting other pathogens that infect the gastrointestinal, respiratory, or reproductive tracts.
What to Watch
The two-fold increase in mucosal antibodies is measurable but modest. The rat model does not guarantee efficacy or dosing tolerability in humans. The team's next milestone is large-animal testing with co-formulated vaccine and adjuvant (rather than separate injections), a step that will clarify whether the approach scales beyond rodents.
Vaccine program planners should request efficacy and safety data from large-animal trials before treating this as a near-term option. The timeline remains 2+ years for a candidate ready for early human evaluation, and regulatory approval would follow conventional paths for new vaccine formulations.