For more than a week, global attention to Afghanistan has focused on the Taliban’s stunningly swift return to power, and the international airlift that is getting diplomats, Western workers, and refugees out. But a small cohort of disease experts is riveted by the political turnover for another reason: They worry it could undermine the long campaign to eradicate polio, which hinges on that country—and where, after years of disappointments, success now seems close.
Since 1988, a dogged and very expensive international campaign has chased polio from most of the world. Afghanistan is one of only two countries in which the circulation of wild poliovirus has never been interrupted; Pakistan, with which it shares a long border, is the other. Case counts have ebbed and spiked as religious and political factionalism interrupted delivery of vaccines to children, and they surged again last year, to 140 cases in the two countries, after the Covid pandemic forced a three-month halt in the vaccination campaign.
But the numbers right now are impossibly good: There has been just one case of polio in each country this year—both of them in January—and many fewer viruses found in sewage, a key surveillance technique, than in past years. It is a fragile moment in which to face a comprehensive change in government, and the health officials who have brought the campaign this far are collectively holding their breath.
“We are in an incredible epidemiological window right now, in both Afghanistan and Pakistan,” says Hamid Jafari, a physician and director of polio eradication for the World Health Organization’s Eastern Mediterranean Region, which stretches from North Africa through the Middle East to Pakistan. “We are seeing very, very low levels of wild poliovirus transmission in both countries—so low that it is unprecedented. It creates a tremendous opportunity for the program to pounce on this low viral burden and just stop it.”
To be clear, the polio campaign in Afghanistan has not ceased, and there is no indication that the Afghan Taliban leadership will require it to. Last week, the Global Polio Eradication Initiative, the formal name for the campaign, put out a statement that it is “currently assessing immediate disruptions to polio eradication efforts and the delivery of other essential health services, to ensure continuity of surveillance and immunization activities while prioritizing the safety and security of staff and frontline health workers.”
Like case counts, the Afghan Taliban’s attitude toward eradication activities also has ebbed and flowed. In its first turn in power in the 1990s, the Taliban allowed the campaign (a coalition of the WHO, the Centers for Disease Control and Prevention, the Gates Foundation, and Rotary International) to begin to operate in Afghanistan. But in 2018, it forced a pause in areas it controlled, banning teams of vaccinators from going house to house in neighborhoods, and then disallowed mass vaccinations at public buildings such as mosques.
Those bans, along with similar pauses in Pakistan as political parties jockeyed for power, were responsible for spikes in polio case counts: from a total of 33 cases in the two countries in 2018 to 117 in 2019. Interruptions that last a long time can be critical blows, because it takes many rounds of the oral vaccine drops to immunize a child. (Even in the US and western Europe, which use an injectable formula, it takes three rounds to solidify immunity, and a fourth school-age booster to lock it in.)
“We estimate that about 3 million kids really didn't have access to services between 2018 and 2020,” says John Vertefeuille, an epidemiologist and the CDC’s polio eradication branch chief. That would have left those children—some partly vaccinated and others born after the bans began—vulnerable to the virus and the floppy paralysis it causes, and would have amplified the amount of virus present in the environment as kids became infected and transmitted it to others.
That case counts are as low as they are right now may be an effect of the pandemic; in the same way that masks, social distancing, and suspending travel squashed last year’s flu season, they may have chilled polio transmission, too.
Organizers are eager to capitalize on those gains, but right now they are waiting for the political situation to settle, and to see what will be allowed. Immunization in Afghanistan has never been easy, but the effort might face harder challenges now. The campaign relies on mobile teams who trek into remote areas and also monitor borders to reach refugees and migrant groups. Yet highways have reportedly been interrupted by checkpoints, and with an anti-Taliban resistance rising, travel may be more hazardous than before. Another unknown will be the status of women in a Taliban-led society. In its earlier turn in power, the group restricted women from working or moving about in public. Yet many of the frontline vaccination teams and community mobilizers who persuade families to accept the vaccine are female. At a news conference in Kabul Tuesday, a Taliban spokesman said working women should stay home for the time being, but promised the restriction would be short.
Jafari points out that the 2018–19 bans were never specifically positioned as opposition to vaccination; the Taliban leadership thought large gatherings were a security risk, providing targets for US or Afghan air strikes. “Now the situation has changed,” he says. “It is very likely that some of the underlying drivers of those bans will become irrelevant.”
If vaccination can resume and quash the wild virus in the two countries, it will not be the longed-for end of polio—yet. The international campaign has a second battle to fight in Africa, where a strain of the noninfectious virus used in the oral vaccine has mutated back to infectiousness. This is a long-recognized danger of the oral vaccine, which relies on a weakened live virus that replicates in the recipient’s gut: Roughly once in every 2.5 million doses, the weakened virus reverts to the ferocity of the wild type.
That would not matter if vaccination was comprehensive and efficient and children everywhere were protected as rapidly as possible. But where vaccines are not delivered regularly, or where campaigns have been suspended by political unrest, the mutated variety, known as circulating vaccine-derived polio virus, has a chance to spread. It is in more than 20 countries in sub-Saharan Africa at the moment. Eliminating the wild virus in Afghanistan and Pakistan would allow the international campaign to fight on just one front instead of two—while vaccinating more children would protect them against both virus types.
At this point, the campaign is waiting for the new political situation in Afghanistan to reveal what may be possible. “I think that the work right now is identifying where decisions are going to be made, to make sure that communication lines remain open that allow for discussion about whether polio services can proceed,” Vertefeuille says. “We're hopeful. We have heard reports from the field that in a lot of the country, health facilities are able to function, health staff have been encouraged to go to work. If health services are viewed as a value, we have an opportunity to get the polio vaccine placed as something that is really necessary for the community.”
Meanwhile, the campaign is working to position polio vaccination as something that transcends politics, and should be allowed to proceed no matter who is in power. “In the past, even when there was divided control of the country, international players were able to negotiate access for vaccinators. So we should not assume this will not be accepted,” says Saad Omer, an epidemiologist and director of the Yale Institute for Global Health. “Let the people on the ground sort this out. That’s our best hope.”
Update 8-25-2021 12:04 PM: This story was updated to correct John Vertefeuille's job title.