Polio is a highly infectious disease spread mainly through contamination by faecal matter, used to kill and paralyse thousands of children annually. While there is no known cure, three injections of the vaccine provide nearly 100% immunity.

Governments and foundations aim to end polio in Pakistan and Afghanistan, the last two countries where the virus continues to circulate.

“The last steps to eradication are by far the toughest. But our foundation remains dedicated to a polio-free future, and we’re optimistic that we will see it soon,” said Mark Suzman, CEO of the Bill & Melinda Gates Foundation, which is run by Microsoft Corp co-founder Bill Gates and his ex-wife Melinda French Gates.

Last month, the Pan American Health Organization (PAHO) said Brazil, the Dominican Republic, Haiti and Peru are at very high risk for the reintroduction of polio. New York state is accelerating efforts to vaccinate residents after the virus was detected in wastewater samples. Cases were also detected in London and Jerusalem.

In March, a senior World Health Organization official said that the world is at a ‘dangerous moment’ in the fight against diseases like polio, after an outbreak in Malawi.

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The announcement came ahead of a key pledging moment that will be co-hosted by Germany and the Global Polio Eradication Initiative (GPEI) on Oct. 18. The Gates Foundation is part of the GPEI, a major project between governments and international organisations. The foundation has contributed nearly $5 billion to GPEI.