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Science’s COVID-19 reporting is supported by the Pulitzer Center.
The COVID-19 pandemic is imperiling the worldwide, 3-decade drive to wipe out polio. In an unprecedented move, the Global Polio Eradication Initiative (GPEI) has recommended suspending polio vaccination campaigns to help stop the spread of the novel coronavirus.
On 24 March, GPEI’s leadership called on all countries to postpone until at least the second half of this year both mass campaigns to boost immunity to the polio virus and the targeted campaigns underway in Africa to stop outbreaks sparked by the live virus vaccine itself.
The implications are “huge,” says Kim Thompson of Harvard University, who heads one of three modeling groups GPEI has charged with analyzing the possible impacts of the pause. More children will be paralyzed by both the wild and vaccine-derived viruses, and the virus will likely reinvade countries that are now polio-free, GPEI concedes. And polio is only one of several diseases for which mass vaccination efforts will be suspended.
“We are caught between two terrible situations,” says GPEI head Michel Zaffran of the World Health Organization (WHO). Going door to door delivering drops of oral polio vaccine (OPV) would put both communities and health workers at risk of infection with the novel coronavirus. Halting polio campaigns will enable GPEI to free up its extensive resources, including surveillance systems and tens of thousands of frontline health workers, to aid in the COVID-19 fight, he says.
“We have no choice,” Zaffran says. “We did not want to have the program be responsible for worsening the situation with COVID-19.”
But the mass polio vaccination campaigns—during which specialized teams fan out across entire countries—are essential to eliminating the wild virus from its last two vestiges, Afghanistan and Pakistan. Without them, the virus will surely rebound, Zaffran says. He is especially worried about countries with weak health systems and low immunity to polio, such as Iraq, Somalia, Yemen, and Syria. They could see the disease return if virus from Afghanistan and Pakistan jumps borders.
On 26 March, WHO’s Strategic Advisory Group of Experts on Immunization (SAGE) recommended all preventive mass vaccination campaigns for other diseases, including measles and yellow fever, be temporarily suspended. Both Zaffran and the expert group stress that routine immunization at clinics and doctor’s offices against polio and all other vaccine-preventable diseases should continue.
Meanwhile, Africa is at risk of additional outbreaks of vaccine-derived polio virus, which arise when the live virus used in OPV mutates and regains its ability to paralyze and spread. To date, the type 2 component of the vaccine has caused most of these outbreaks, which paralyzed 350 children on the continent last year and have proved unexpectedly difficult to stamp out. Thompson worries the pause will also spawn outbreaks of the other two serotypes in OPV, types 1 and 3, which have so far been “largely a theoretical concern.”
The “painful” decision to suspend campaigns was made at the highest levels of GPEI, with the endorsement of WHO Director-General Tedros Adhanom Ghebreyesus, says Rebecca Martin, who heads the Center for Global Health at U.S. Centers for Disease Control and Prevention, one of the partner organizations in GPEI. “We very much agreed,” she says.
Countries could ignore the strong advice to pause, Martin says: “GPEI does not have control” if they decide to proceed with campaigns anyway. But they should do so only after a thorough assessment of the risk to health workers and communities, and under the strictest safety precautions, GPEI says. “It will be very difficult to do in a safe manner,” Zaffran says.
Modelers are gearing up to look not only at possible impacts of the pause, but also at the implications of various vaccination strategies, once they can resume. One hope is that travel restrictions, closed borders, and physical distancing to slow COVID-19 will help blunt the spread of polio as well, but Martin is not so sure. “We’ve seen with different infectious diseases that there are always ways of crossing borders,” she says.
GPEI won’t be idle in the interim, Zaffran says. Surveillance for polio virus must continue, and as much as possible be paired with surveillance for COVID-19. The program will work with manufacturers to try to ensure enough OPV is available when campaigns resume—a challenge because the vaccine is already in short supply. And development and approval of a safer OPV type 2 that has a lower chance of reversion, must continue “full speed.”
Martin and others stress that GPEI must be able to come out of the gate hard and fast with vaccination campaigns once it is safe to do so. The program will regularly evaluate the situation to decide when that moment has arrived. “There is no wavering in the commitment for polio eradication,” Martin says, “but we are in a place the world has never been.”
Source: Science Mag