Locking Away Poliovirus: Progress on Global Containment, 2019–2020

Why containment matters

Since the Global Polio Eradication Initiative began in 1988, wild polio cases fell from 350,000 in 125 countries to 176 in just two in 2019. Wild poliovirus type 2 was declared eradicated in 2015 and type 3 in 2019; type 1 remains endemic in Afghanistan and Pakistan.

An eradicated virus could still escape from a laboratory or vaccine plant holding it. So in 2015 World Health Organization (WHO) member states agreed to keep all type 2 poliovirus — wild, vaccine-derived and vaccine strain — only in certified poliovirus-essential facilities meeting a global standard (known as GAPIII). Countries also agreed to:

• report their type 2 inventories every year;
• destroy materials they don't need;
• if keeping any, set up a national authority for containment and an audit process.

Since October 2019, the same rules apply to wild type 3.

The vaccine problem behind it

The eradication effort relied on the live oral vaccine covering all three types. Where too few people are immune, vaccine virus can keep spreading and mutate into vaccine-derived poliovirus that paralyzes — and cause outbreaks. Because most of these were type 2, the world switched in 2016 to an oral vaccine covering only types 1 and 3, with a dose of injectable vaccine for type 2 protection. But low coverage and shortages of injectable vaccine left big immunity gaps, and outbreaks of vaccine-derived type 2 spread, especially in Africa and parts of Asia. Since the switch, WHO's lab network has detected 41 such outbreaks, many likely seeded by the type 2 oral vaccine used to fight them.

Where things stood in 2020

As of August 2020:

• 25 countries planned to keep type 2 materials in 73 designated facilities — but none had yet been certified.
• 22 of those countries had set up containment authorities; some, including China, Romania and the United Kingdom, hadn't yet given them legal power.
• 32 of the 73 facilities had a Certificate of Participation in the certification scheme. The deadline to apply was December 31, 2019, and certificates expire in April 2021.
• The first certification audits, planned for 2020, were delayed by COVID-19, as was the qualification of 10 lead auditors; a new multiyear plan is being prepared.
• In 2019, the initiative ran four webinars and six week-long in-person trainings for facilities.

New rules for new vaccines

• A WHO Containment Advisory Group, set up in 2017, is revising the standard; an updated version is expected in 2021. In March 2020 it decided that novel type 1 and type 3 oral vaccines count as types 1 and 3 for containment purposes.
• Novel type 2 oral vaccine, engineered to be more genetically stable and far less likely to seed outbreaks, was expected for first use in October 2020 under WHO's Emergency Use Listing. It may be made and used outside full containment, but with strict inventories, vial tracking and extra environmental surveillance.
• Where more than one type circulates, the three-type oral vaccine is being brought back for outbreak response, with the WHO director-general's approval, to boost gut immunity quickly against all three types.
• Countries must report their use and stocks of these vaccines to their containment authorities and national certification committees each year.

What countries should do

The 2018 World Health Assembly urged all member states to speed up containment. Countries planning to keep type 2 materials should ask whether they really need them; after a vaccine-derived outbreak ends, remaining samples should be inventoried and destroyed or moved to a certified facility; and every vial of type 2 vaccine should be tracked from release to use or destruction. The type 3 vaccine strain isn't yet subject to containment, as there are no immediate plans to stop using it. Above all, countries with facilities must set up legally empowered containment authorities and submit their Certificates of Participation.

Countries planning poliovirus-essential facilities for type 2 materials (blue). Figure from the CDC report.

Sources

Based on Daphne B. Moffett, Anna Llewellyn, Harpal Singh and others (World Health Organization, the Global Polio Eradication Initiative, CDC, the Bill and Melinda Gates Foundation and Rotary International), "Progress Toward Poliovirus Containment Implementation — Worldwide, 2019–2020," MMWR, Centers for Disease Control and Prevention; published by CDC and in the public domain; rewritten in hubnx's own words.