Polio Cases on the rise - WHO - Seeker's Thoughts

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Polio Cases on the rise - WHO

 The world has been fighting against polio through massive vaccination efforts since 1988. It has helped a lot to reduce the number of cases by more than 99% worldwide – however, there remains a worry. 

According to the weekly Epidemiological record by WHO, there have seen a high spike of polio cases in between 2010 and 2019. In May 2020, a total of 149 immunodeficiency VDPV (iVDPV) cases had been reported to the WHO between January 1961 and December 2019.

According to the WHO Report, The polio cases reported increased over time: at least two out of three cases 66% reported so far were detected between 2010 and 2019, out of these, 59% occurred in children aged less than two years. About 60% of cases were reported in males; and 64% of patients had acute Flaccid Paralysis (AFP), the most severe sign-on polio, as the first symptom.

In July 2018- December 2019, about 16 new iVDPV cases reported from five countries – Argentina, Egypt, Islamic Republic of Iran, Philippines, and Tunisia according to the WHO.

Also Read,

Polio vaccinations campaigns restart again due to the higher risk of a polio outbreak

Amid COVID-19 pandemic, the Global Polio Eradication Initiative (GPEI) unexpectedly halted all mass vaccination campaigns in March, worried they could inadvertently spread the novel coronavirus

This move further imperiled the troubled 3-decade drive to wipe out polio.

Now the GPEI and the countries it supports are resuming vaccination campaigns. According to Michel Zaffran, polio cases are surging in many countries, and models paint a pretty bleak picture. If the campaign doesn’t start soon. For now, countries will only be responding to outbreaks; preventive campaigns remain on hold.

Back in March, when COVID-19 began to spread around the world, no one knew whether the door to door polio campaigns would make things worse.

The cost was enormous. There’s a growing sense that the collateral damage of pausing campaigns is really substantial.

In urgent recommendations in late May, GPEI said it expected circulation of polioviruses to increase exponentially during the upcoming high season, raising the possibility of uncontrolled multi-country outbreaks.

The Polio campaign on the pandemic is likely small in places where the virus is already raging. The outbreak has its own momentum and acceleration. In areas where COVID-19 has yet to hit, however, the risks are substantial. To lower them, vaccinators will be screened for COVID-19, wear masks, use hand sanitizer, and practice physical distancing as much as possible. Most important, according to WHO’s head for polio eradication in Pakistan and Afghanistan, the team will work in their own communities.

In Pakistan and Afghanistan the polio campaign was in a rut even before COVID-19, the last bastions of the wild virus, cases of wild-type polio shot up last year to 176, from 33 in 2018, driven by rumors refusal, and in Afghanistan, the Taliban’s outright ban on vaccination. So far this year, the two countries have confirmed 87 wild polio cases, compared with 64 at this time last year. The real number is likely higher because the pandemic has hampered surveillance.

The situation is more alarming still, Pakistan and Afghanis are battling outbreaks if vaccine-derived poliovirus as well – the only two countries facing that double challenge. Such outbreaks occur when the weekend virus used in the oral polio vaccine- usually the type 2 component of three poliovirus serotypes – mutates and regains its ability to paralyze and spread. Type 2 vaccine-derived cases in Pakistan and Afghanistan soared from 16 at this time in 2019 to 79 so far. The numbers look awful for eradication.

The reason is that most children under age 5 have little or no immunity to vaccine-derived virus type 2 because the world stopped using OPV2 in 2016- a first step toward pulling OPV from the use altogether in hopes of preventing vaccine-derived outbreaks. That hasn’t worked and not the number of vulnerable kids is growing every year.

What are Vaccine – derived polioviruses?

Vaccine- derived polioviruses are rare strains of poliovirus that have genetically mutated from the original strain in the oral polio vaccine. Oral polio vaccine contains an attenuated weakened vaccine-virus, which activities and immune response in the body.

When a child is vaccinated, the weakened vaccine-virus replicates in the intestine and triggers a protective immune response. But when the child excretes the vaccine-virus (for about six to eight weeks), some of the vaccine-virus may no longer be the same as the original one: it gets genetically mutated during replication. This is called a VDPV.

According to WHO, there is evidence of community transmission in the case of iVDPV – if a population is poorly vaccinated, there would be enough susceptible children for the excreted vaccine-derived polioviruses to begin circulating in the community.

And there are four types of VDPBVs – circulating vaccine-derived poliovirus (cVDPV); immunodeficiency related vaccine-derived poliovirus (iVDPV); and ambiguous vaccine-derived poliovirus (aVDPV; and ambiguous vaccine-derived poliovirus (AVDPV).

If the vaccine virus is able to circulate for a long time, it can mutate and regain virulence. These viruses are called cVDPVs.

Usually, iVDPV is observed in children with rare immune deficiency disorder. Children with iVDPVs are unable to mount an immune response and are, therefore, unable to clear the intestinal vaccine virus infection. The two major risks that iVDPV pose is that of the profession to paralysis AFP and death.

In most of the countries with AFP surveillance detected iVDPV in paralyzed children who then received a diagnosis for a primary immunodeficiency PID, but instances of iVDPV were also found in PID patients with no paralysis.

Spike in cases and risks

According to the WHO half of the cases detected cases during 2010-2019 were in the WHO Eastern Mediterranean Region; the report attribute recent higher PID surveillance and a high rate of consanguineous (when partners are from the same kinship) marriages, leading to a high prevalence of paid, as the reason of the increase in reported cases there.

More surveillance to get a better sense of VDPV outbreaks, including iVDPV should be carried out.


There is an urgent need for global efforts to enhance vaccine coverage in all parts of the world, which will lessen the risk of VDPV in the community. The report also points to the need to hasten the transition of phasing out OPV usage in all countries to avoid the risk of VDPV, which can stop wild poliovirus transmission. There is a need to shift to an inactivated polio vaccine to maintain population immunity levels.

WHO has earlier supported pilot projects for Ivdpv surveillance in children with PID in several countries, including Egypt, Islamic Republic of Iran, Pakistan, Sri Lanka, Tunisia, and, more recently, China and India.

According to the report, Additional countries are being identified in other WHO regions in which to implement systematic surveillance for PID affected children without paralysis.

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