Malawi is launching a mass vaccination campaign against wild poliovirus type 1, which is to extend to 23 million children across five southern African countries, WHO said on Friday.

The campaign, to kick off Sunday, follows Malawi’s declaration of a polio outbreak on 17 February – three months after the first polio virus case in 30 years was identified in a young child in Lilongwe. 

The case was the first in Africa since the region was certified free of indigenous wild poliovirus in 2020. WHO said that the region’s certification as wild polio-free remains unchanged, as the wild poliovirus strain identified had been “imported” from Pakistan. 

So far, no clear explanation of how the Asian virus strain may have infected an African child who had never traveled outside of the country, has been provided by WHO or Malawi health authorities. Nor has there been any explanation of why it took three months between the time the child was diagnosed and the outbreak was formally declared by WHO.

But the breadth of the new campaign makes it clear the incident has been perceived as a major threat to Africa’s wild polio virus free status – with risks of subtle, silent transmission of the virus much more widely, via contaminated water and sewage, food, or human-to-human contact.

Malawi has since set up an environmental surveillance system for poliovirus in 11 cities across four sites, including the Lilongwe District that encompasses the capital Lilongwe, where the initial, and so far only reported case, was detected, WHO said. 

Asked by Health Policy Watch whether traces of the wild polio virus had also been identified in sewage sources, through the environmental surveillance, WHO did not reply as of publication time.  

Targeting children across four countries – then Zimbabwe

More than 80 million doses will be administered to more than 23 million children under 5 years in a four-round vaccination campaign in five southern African countries, WHO said. 

The first phase of the campaign, beginning this month, will target 9.4 million children across Malawi, Mozambique, Tanzania, and Zambia. Three subsequent rounds – with Zimbabwe joining the campaign- are set for April, June, and July, and aim to reach more than 23 million children with more than 80 million doses of the bivalent Oral Polio Vaccine recommended by the World Health Organization (WHO). 

“Polio is a highly infectious and an untreatable disease that can result in permanent paralysis. In support of Malawi and its neighbours, we are acting fast to halt this outbreak and extinguish the threat through effective vaccinations,” said WHO Regional Director for Africa Dr Matshidiso Moeti. 

“The African region has already defeated wild poliovirus due to a monumental effort by countries. We have the know-how and are tirelessly working to ensure that every child lives and thrives in a continent free of polio.”

Single case of polio in Malawi linked to Pakistan strain

Laboratory analysis has linked the strain detected in Malawi to the one circulating in Pakistan’s Sindh Province in 2019. 

In addition to environmental surveillance, WHO has also been supporting the country to reinforce response measures including risk assessment, and preparations for the vaccination campaigns. A surge team from WHO is working with country-based counterparts, partner organizations, and the government to end the outbreak. 

The WHO team is a part of a broader multi-partner Global Polio Eradication Initiative to support the country.

In an unrelated event,  a vaccine-directed case of polio was also identified in February by Israeli authorities in Jerusalem, also for the first time in 30 years. The infected child is part of an ultra-orthodox Jewish community in which vaccination rates hover at around 50% or less. A vaccination drive also was launched in the city.  

Polio, a viral disease with no cure, can invade the nervous system and can cause total paralysis within hours, particular among children under 5 years. The virus is transmitted from person to person, mainly through contamination by fecal matter or, less frequently, through contaminated water or food, and multiplies in the intestine.

While there is no cure for polio, the disease can be prevented through administration of a vaccine.

Image Credits: Sanofi Pastuer/Flickr, Sanofi Pastuer/Flickr.