New diagnostic tool will strengthen polio eradication efforts

June 11, 2019 by PATH

Development of testing for primary immunodeficiency diseases will support polio eradication efforts

Development of a new diagnostic test for primary immunodeficiency diseases will support polio eradication efforts

As part of multi-pronged eradication efforts, PATH is advancing a rapid diagnostic screening test to help detect a class of rare genetic diseases that presents a unique risk for spreading the poliovirus.

The number of polio cases globally has dropped by more than 99% since 1988, but the danger persists that polio will again infect tens of thousands of children annually. Preventing the spread of the highly infectious disease, which can cause total paralysis, relies on eradication of polio. The new test is part of broad global eradication initiatives.

Oral polio vaccine

The oral polio vaccine has been a key tool in polio eradication initiatives, preventing more than 13 million polio cases globally. The oral polio vaccine uses a weakened version of the polio virus that replicates in the intestines for a short period of time while the body builds immunity.

During that short period of time, the weakened vaccine-polio virus is shed through human waste. Where there is limited sanitation and low vaccination rates, the vaccine-polio virus can circulate in the community due to the shedding for a short time before dying out, sometimes even providing passive immunity to other children while circulating. However, if the circulation continues for a long period of time in a community with low vaccination rates, in extremely rare cases, the weakened vaccine-derived virus can strengthen to become as dangerous as the virus it was meant to protect against.

Primary immunodeficiency diseases

People with a rare class of hereditary diseases, called primary immunodeficiency diseases, are often not able to mount an adequate immune response to clear the weakened polio virus from oral polio vaccine. This means they are far more likely to shed the virus for a prolonged period of time, increasing the risk of mutation into a vaccine-derived polio virus that can cause paralysis.

PATH is pushing forward development of a rapid diagnostic test that helps detect primary immunodeficiency diseases by identifying low antibody levels that are a sign of the group of diseases. A rapid diagnostic test will equip communities with an important tool to help identify undiagnosed cases of primary immunodeficiency diseases and limit prolonged shedding of vaccine polio virus. The availability of a rapid diagnostic test, which can be performed in any setting, could be particularly important in rural and low-resource settings. Currently, testing is often only available in reference centers located in major cities, which makes it difficult for many people to access.

This test could become even more important when wild polio virus is eradicated. Individuals with prolonged shedding of vaccine polio virus could be the final reservoir of the polio virus at that point. Screening and diagnostic tests will be important tools that work in tandem with medications that are being developed and evaluated to clear the virus from those individuals.

This project is supported by the Bill & Melinda Gates Foundation.

A long history of strengthening polio eradication efforts