BLANTYRE, Malawi (AP) - In a classroom in southern Malawi, children sit in rows on the floor as a health worker moves among them administering an oral vaccine that protects against polio.
The new vaccination campaign that began on Wednesday is another reminder that the world still hasn’t managed to eradicate the ancient disease, which primarily affects children and can cause paralysis, despite a concerted effort for more than 35 years by the World Health Organization and its partners.
Health officials believe they came close several times, including five years ago when just five cases of the natural polio virus were reported globally.
But a WHO report said that there were 38 cases of the natural polio virus between January and October 2025 - all in Pakistan and Afghanistan, the last two countries where it remains endemic - and another 151 cases of a vaccine-derived polio virus strain in 13 countries.
Those vaccine-derived cases have overtaken natural polio virus cases in recent years and complicated the eradication effort as one of a number of missteps in the global fight. They come about when the weakened live virus in oral polio vaccines mutates into a form capable of sparking new outbreaks.
That’s the problem in Malawi, which reported last month that it had discovered the vaccine-derived Type 2 polio virus strain in sewage water in the southern city of Blantyre, prompting health authorities to launch a new immunization campaign using a modified vaccine.
By WHO regulations, Malawi was required to declare an outbreak on confirming the polio virus traces.
Malawi’s deputy health minister, Charles Chilambula, was among the officials promoting the vaccination drive. It involves 1.7 million doses being administered to children at schools and taken door-to-door through some of the city’s neighborhoods by health workers.
In an attempt to reassure people, Chilambula said that the doses will protect against the vaccine-derived form that’s been discovered in Blantyre in environmental samples. Malawi’s Health Ministry said that it's using the novel oral polio vaccine that’s designed to stop circulating vaccine-derived Type 2 outbreaks.
“It’s very important that we do the vaccine now, because it also deals with this virus which we have detected,” Chilambula said.
Polio is a highly contagious incurable disease that affects the nervous system, and both the wild virus and the vaccine-derived strain can cause irreversible paralysis. It's spread through contaminated food or water. Around one in 200 cases results in paralysis, WHO says, typically affecting the legs.
In the early 20th century, polio struck fear in communities across the world and paralyzed hundreds of thousands of children annually before the advent of vaccines in the 1950s.
Despite statistics now showing more children contracting polio viruses originating in vaccines than in the wild, global health authorities claim a bigger victory against polio. Wild polio virus cases have decreased by more than 99% since 1988, according to WHO, and from 125 endemic countries to two, largely because of vaccines.
But the end goal - the eradication of polio like smallpox - has been elusive.
Malawi became a country of concern for polio again in 2022 when a child contracted the wild polio virus, the first case in the southern African nation for 30 years. Last month’s announcement of traces of a vaccine-derived strain is another setback.
Dr. Joe Collins Opio, UNICEF's Malawi chief of health, said that the vaccination campaign would first focus on children in eight districts but would ultimately grow into a national effort across the country of around 22 million people and called on everyone to "be part of the response."
Malawi, like many poor countries, relies heavily on mobile health workers to reach people in vaccination campaigns.
Health workers, mainly women in matching blue dresses, visited schools and homes in the Blantyre area on foot, carrying vaccines in small cooler boxes. Officials say motorbikes will be used to take doses further afield.
People were also invited to open-air educational events, where officials promoted vaccines in speeches interspersed with popular music as children held up signs urging they be protected from polio.
"Polio remains a threat," said Dr. Akosua Sika Ayisi, a public health specialist with WHO helping with the vaccination drive. She outlined Malawi´s task of ensuring every eligible child "in every community" is fully vaccinated to contribute to the global eradication of polio.