New Delhi: A revised international polio eradication strategy has been envisioned to aggressively address outbreaks of the disease in areas where it is still endemic.
The Global Polio Eradication Initiative (GPEI) — a public-private collaboration between countries and health groups — released a summarised version of the strategy Wednesday, which proposes to eradicate polio all over the world by 2026. The final strategy document will be released by January 2022.
The strategy will address countries where polio outbreaks are still considerably common as well as the regions that are seeing a rise in type 2 circulating vaccine-derived poliovirus (cVDPV) cases. It is a rare form of the disease that spreads from the oral vaccination itself in under-immunised populations.
Wild poliovirus types 2 and 3 (WPV2 and WPV3) were declared eradicated in 2015 and 2019, and southeast Asia was declared free of poliovirus by the World Health Organization in 2014. In August 2020, the WHO African Region was certified free of wild poliovirus (WPV) in August 2020.
However, wild poliovirus type 1 and cVDPV continue to circulate, particularly in Pakistan and Afghanistan.
The two main goals envisioned by GPEI are to “permanently interrupt all poliovirus transmission in endemic countries” and “to stop cVDPV transmission and prevent outbreaks in polio-free regions”.
“Under the Polio Eradication Strategy 2022−2026, the programme will shift from current need-based approaches to embrace systematic and pragmatic political advocacy efforts,” the document notes.
India began a polio immunisation programme in 1995 and recorded its last case in 2011. Poliovirus types 1 and 3 were prevalent in the country and it was finally declared polio-free by 2014.
The feat was managed through the efforts of the Indian government, Rotary club, and UNICEF among others.
Also read: How to ensure smooth Covid vaccine rollout — India’s polio programme has some lessons
Pakistan and Afghanistan still affected by polio
While large parts of the world have eradicated the virus, polio is still endemic in both Pakistan and Afghanistan.
In Afghanistan, restrictions on house-to-house campaigns in southern areas have resulted in more than 1 million children missing scheduled vaccinations since May 2018, including “zero-dose” children who have received “no essential immunization”.
In Pakistan, according to GPEI, “Progress has been impeded by vaccine hesitancy and a misalignment between challenges on the ground in priority areas and programme efforts to overcome these challenges”.
The Pashto-speaking communities, which make up 15 per cent of the country’s population, accounted for 81 per cent of the WPV1 cases over the last decade.
“Modelling suggests that a failure to eradicate WPV1 in these last two endemic countries could result in a global resurgence in wild polio transmission, leading to 200,000 new polio cases annually within 10 years,” states the strategy report.
In Pakistan, the strategy proposes to “design targeted interventions in underserved areas with high levels of mistrust,” as well as “building alliances with communities to encourage leaders and influencers to become champions for eradication”.
Meanwhile, in Afghanistan, an integrated service delivery is expected to ensure high immunisation coverage.
GPEI will collaborate with NGOs and also support government efforts to ensure a robust vaccination programme and strengthen the campaign against the poliovirus in these countries.
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Vaccine-derived polio outbreaks
The second area of concern is outbreaks in polio-free regions caused by cVDPV or the type 2 circulating vaccine-derived poliovirus.
Polio vaccines are of different types, which may contain one, a combination of two or all three different serotypes of attenuated vaccine. An attenuated vaccine contains live virus with reduced virulence.
The switch between trivalent oral polio vaccines (those with all three types of polioviruses) and bivalent oral polio vaccines (with only types 1 and 3) in 2015 and 2016, combined with delays in implementing the inactivated polio vaccine (IPV) led to decreasing immunity to type 2 poliovirus.
“As a consequence, outbreaks of cVDPV2 have become as great a public health threat as WPV1, with more cases of cVDPV2 than WPV1 annually since 2017,” noted GPEI.
To tackle these new outbreaks, the initiative proposes scaling up the production of the new vaccine for the type 2 virus — novel oral polio vaccine type 2 (nOPV2). Like the OPV, the new vaccine also uses a form of a live virus, but it has been genetically modified to prevent it from becoming virulent.
“Because of the anticipated reduced risk of nOPV2 seeding new outbreaks, it will be possible to increase the scope of vaccine use in OPV2-naïve populations and allow countries to stop transmission and prevent spread outside response zones,” noted the GPEI document.
Also read: Why Pakistan has been unable to immunise its population against polio