A date to remember: on 25th August 2020, the WHO African region was declared free of wild polio, four years since its last case, by the independent Africa Regional Certification Commission for Polio Eradication. [1] During this uncertain time for global health, there may be important lessons to be learned from the development and widespread delivery of the polio vaccine.
The World Health Organisation (WHO) divides its member states into six regions across the world. Following this certification, five out of the six WHO regions are now polio-free - this accounts for 90% of the global population. The only region not yet free of wild polio is the Eastern Mediterranean: Pakistan and Afghanistan are the only two countries in the world remaining with endemic polio. [2]
Definitions:
· Poliomyelitis, commonly shortened to polio: an infectious illness caused by the poliovirus. There is currently no cure for polio, but there is a preventative vaccine.
Background
Polio is a contagious illness, spread through contact with either the faeces or respiratory droplets from an infected individual. It can also be transmitted via contaminated food or water. [3]
While some people recover quickly from polio with no long-term complications, others suffer the effects of polio lifelong. These consequences include impaired growth and development of legs and feet, particularly in children. Muscle weakness and paralysis can develop which, if breathing muscles are affected, can prove fatal. [3]
In the United Kingdom, the polio vaccination is part of the routine immunisation schedule offered to all children. For this reason, there have been no confirmed cases in the UK since 1984. [4]
Obstacles to Eradication
However, encouraging implementation of the polio vaccine across other regions of the world has not been simple. A combination of internal conflict, international disagreements and scandals surrounding vaccination campaigns has historically led to suspicion of the polio vaccine, and a general lack of public confidence in immunisation campaigns.
The Cutter Incident
One early event which damaged public perception of the polio vaccine was the Cutter Incident in the USA, in 1955. Some batches of inactivated vaccine (which should not have contained any living virus) were accidentally distributed containing live poliovirus, resulting in over 250 people contracting polio from the vaccine, and many being permanently paralysed. Unfortunately this incident led to a mistrust of the polio vaccine and a reluctance by many to vaccinate their children. On the other hand, this event marked a positive turning point for increased regulation and stringency in testing vaccines. [5]
Nigerian Boycott
In northern Nigeria in 2003, mistrust of the polio vaccine continued to build as leaders of some northern states claimed that the vaccines were contaminated with HIV, cancer and anti-fertility agents. The leaders propagated the belief that the USA had tampered with the vaccines as part of their War on Terror, following the 9/11 attacks. Political and religious tension surrounding the vaccine led to an 11-month boycott. During this time, the number of cases of polio rose dramatically in Nigeria, possibly a significant reason why it was the last African country to be free of wild polio. [6]
CIA's Fake Vaccination Campaign
More recently in 2011, an espionage operation by the USA's Central Intelligence Agency (CIA), proved heavily detrimental to vaccination uptake in Pakistan. The CIA went undercover posing as a hepatitis vaccination campaign, in a covert attempt to obtain DNA from Osama Bin Laden's children. This was part of an elaborate plan to locate Bin Laden himself, before capturing and killing him. [7]
Although successful in their primary aim, this exercise had a catastrophic impact on the public's trust in vaccination campaigns, including those for the polio vaccine. This even led to repeated events of legitimate polio vaccination staff being attacked in Pakistan as people believed them to be CIA operatives undercover. [8] As a result, in 2014 the White House declared that the CIA would no longer be allowed to pose as vaccination workers undercover. [7]
Unfortunately, scandals like these had already eroded public confidence in the polio vaccine. It is hardly surprising, therefore, that Pakistan is one of the only two countries where wild poliovirus is still present.
Why does Afghanistan still have polio?
Afghanistan is the other country still suffering from endemic wild poliovirus. One reason cited for this is the long-term conflict and political instability in the country, which has made it difficult to set-up established immunisation programmes. Furthermore, the high rates of migration across the border between Pakistan and Afghanistan mean that polio spreads easily and frequently between the two countries. [9]
How was Eradication Finally Achieved in Africa?
Despite the set-backs, there has been enormous progress in reducing global levels of polio through vaccination. Since the Global Polio Eradication Initiative (GPEI) was launched in 1988, the incidence of polio cases globally has fallen by 99%. [10] This progress is largely attributed to improved cooperation between countries and united efforts to increase transparency and education about the vaccine. The growth of campaigns has been possible thanks to several sources of funding including non-governmental organisations, governments and individual philanthropic donors. [1]
Remaining Vigilant: Vaccine-Derived Poliovirus Strains
Whilst wild poliovirus has been eradicated in all but two countries, vaccine-derived poliovirus strains remain affecting 16 countries in the WHO African Region, 90% of which are due to type 2 circulating vaccine-derived poliovirus (cVDPV2). [1] [11]
In order to explain how vaccine-derived poliovirus strains occur, it is necessary to understand the basic theory behind live vaccines. There have been several forms of the polio vaccine during its development: one of these forms is a live-attenuated vaccine, where an alive but weakened version of the pathogen (in this case, poliovirus) is inserted into the body, which triggers the body's immune system to produce antibodies against the virus. This means that when a fully-activated form of the virus is encountered in real life the body will recognise it, through molecules on its surface called antigens, and be able to launch a quicker and stronger response against the poliovirus.
In countries where this vaccination method is employed it is possible, although rare, for the weakened poliovirus in the vaccine to mutate and spread in severely under-immunised communities. [12] The longer this virus survives, the more mutations it may undergo and after approximately 12 months it may become its own strain of poliovirus: a dangerous circulating vaccine-derived poliovirus (cVDPV), which can cause paralysis in the same way as wild poliovirus. It is important to note that these cVDPVs do not indicate a problem with the vaccines themselves, rather they indicate the opposite: that the level of immunisation in that community is too low, leaving people vulnerable to infection, and vaccine usage should be increased. [11]
The Current Situation
At this important milestone of freedom from wild poliovirus in Africa, there is good reason to feel positive at the progress made thus far. As routine vaccination programmes for polio are becoming more established, there is reason to hope that this will boost regular immunisation against other vaccine-preventable conditions. It is vital to continue strengthening local health systems and consolidating vaccination programmes, especially as the COVID-19 pandemic has caused disruption to vaccine schedules. However, it is important to remember that Pakistan and Afghanistan are two countries still suffering from endemic polio, and more work needs to be done to find sustainable solutions in the region. Finally, whilst vaccine-derived polioviruses present a new problem for Africa, the solution still remains to increase vaccination and boost the immunity of communities as a whole.
Author; Deborah Allen, Author; Deborah Allen, MSc Global Health Science and Epidemiology, St Anne's College.
References:
1. World Health Organization. Global polio eradication initiative applauds WHO African region for wild polio-free certification, 25 Aug 2020. [Online] Available from: https://www.who.int/news-room/detail/25-08-2020-global-polio-eradication-initiative-applauds-who-african-region-for-wild-polio-free-certification [Accessed 09/10/2020].
2. Department for International Development and The Rt Hon Anne-Marie Trevelyan MP. Wild polio wiped out in Africa with UK aid support, 25 Aug 2020. [Online] Available from: https://www.gov.uk/government/news/wild-polio-wiped-out-in-africa-with-uk-aid-support#:~:text=Pakistan%20and%20Afghanistan%20are%20now,across%20borders%20and%20proliferate%20again. [Accessed 09/10/2020].
3. National Health Service. Polio, 30 July 2018. [Online] Available from: https://www.nhs.uk/conditions/polio/ [Accessed 09/10/2020].
4. The Vaccine Knowledge Project. Polio (Poliomyelitis), 13 Aug 2018. [Online] Available from: https://vk.ovg.ox.ac.uk/vk/polio#:~:text=The%20last%20outbreak%20of%20polio,all%20countries%20in%20the%20world. [Accessed 09/10/2020].
5. Centers for Disease Control and Prevention. Historical Vaccine Safety Concerns, 04 Sep 2020. [Online] Available from: https://www.cdc.gov/vaccinesafety/concerns/concerns-history.html [Accessed 09/10/2020].
6. A.S. Jegede. What Led to the Nigerian Boycott of the Polio Vaccination Campaign? PLoS Medicine, Mar 2007, 4 (3), p.0418. [Online] Available from: https://dx.doi.org/10.1371%2Fjournal.pmed.0040073 [Accessed 09/10/2020].
7. The Lancet: Editorial. Polio eradication: the CIA and their unintended victims. The Lancet, 31 May 2014, 383 (9932), p.1862.
8. The Lancet: Editorial. Polio eradication: where are we now? The Lancet, 14-20 Dec 2013, 382 (9909), p.1979.
9. Unicef. Polio eradication, [no date]. [Online] Available from: https://www.unicef.org/afghanistan/polio-eradication [Accessed 10/10/2020].
10. Global Polio Eradication Initiative. History of Polio, [no date]. [Online] Available from: https://polioeradication.org/polio-today/history-of-polio/ [Accessed 09/10/2020].
11. World Health Organization. What is vaccine-derived polio?, 19 Apr 2017. [Online] Available from: https://www.who.int/westernpacific/news/q-a-detail/what-is-vaccine-derived-polio [Accessed 09/10/2020].
12. Giorgia Guglielmi. Africa declared free from wild polio — but vaccine-derived strains remain, 28 Aug 2020. [Online] Available from: https://www.nature.com/articles/d41586-020-02501-3 [Accessed 09/10/2020].