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New Polio Vaccine From Modified Virus Shows Promising Results In Trials

In the last few years, relentless vaccination campaigns had eradicated polio by 99% from the world. More than 13 million children were saved from the risk of potentially debilitating paralysis due to polio.

But recently, the efforts were troubled by vaccine-derived polio outbreaks. The weakened virus used in the 50-year-old polio vaccine evolved the ability to infect humans and spread in communities.

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Now, Andrew Macadam, Ph.D., of the UK’s National Institute for Biological Standards and Control (NIBSC) and UC San Francisco virologist Raul Andino, Ph.D., with support from the Bill and Melinda Gates Foundation is reporting promising Phase 1 clinical results for the first new oral polio vaccine in 50 years, that is incapable of evolving the ability to cause disease in humans.

Andino and colleagues in their 2017 study had discovered that the virus used the same three evolutionary steps to mutate from harmless vaccine into a regional menace in every vaccine-derived polio outbreak they studied.

The team of researchers employed clever genetic wizardry based on decades of study of the poliovirus’s biology to redesign the vaccine to ensure that it is incapable of following this three-step pathway to re-evolve virulence.

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They modified the region of the genome that is crucial for the virus to re-evolve and infect humans. They also made sure that the virus cannot get rid of this even by exchanging genetic material with other viruses.

Andino, a professor of microbiology and immunology at UCSF, said this is the first time scientists are designing a live attenuated virus on the basis of a detailed understanding of its biology, rather than blindly massaging the virus in animal cells to remove its ability of human virulence.

The double-blinded Phase 1 clinical trials were carried out in 15 adult volunteers who were previously vaccinated with the inactive polio vaccine, to make sure they don’t get infected with the live vaccine.

The new live vaccine was found more effective and stable than the 50-year-old vaccine from which it was derived. The volunteers developed plentiful antibodies in response to the new vaccine. Though viral particles were shed in their stool, the particles were unable to cause disease in mice. But the previous studies had shown that the viral particles shed from people vaccinated with the standard Sabin oral polio vaccine developed paralysis in 90% mice.

The World Health Organization is planning a phase 3 trial for the vaccine to fast track its development and use them to contain vaccine-derived outbreaks.

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But the efforts to eradicate polio from the world were suspended during this Covid-19 pandemic. Andino and his team are now applying all that they have learned from developing the live polio vaccine to the search for a Covid-19 vaccine. They are also involved in developing a mice model to study how the virus spreads and causes disease.

Many scientists across the world are trying to develop a vaccine using both traditional techniques and RNA-based techniques. But Adino is trying to better understand the biological pathways within the virus that might help in developing an effective and safe live attenuated vaccine. Ming Te Yeh of UCSF was the lead author of the study that developed the polio vaccine from a modified virus. Andino and Macadam co-led the study.