When smallpox was eradicated in 1980, hopes were high that the polio virus would be next. Since the launch of the eradication campaign in 1988, two out of three subtypes of the virus have been successfully eradicated, and the third is under control. In the past year, only 21 cases of wild polio have been reported in children from Afghanistan, Pakistan, and Mozambique.
However, the cases of other types of polio remain high and concerning. Last year, 665 cases of vaccine-derived polio were registered in 23 countries. Vaccine-derived polio occurs when the weakened poliovirus used in oral vaccines regains its virulence.
In a recent issue of the prestigious scientific journal Nature, Andrew Macadam and his colleagues at the National Institute for Biological Standards and Control in South Mimms, UK, report on the development of new oral polio vaccines. These vaccines, designed to reduce the likelihood of outbreaks of types 1 and 3 poliovirus, were created using a method previously employed for a new type 2 polio vaccine known as nOPV2.
The scientists utilized genetic engineering techniques to significantly decrease the chances of the weakened virus regaining its virulence. The two new vaccines were tested in mice and found to be effective, safe, and stable. They are currently undergoing human trials. If their safety and efficacy are comparable to the nOPV2 vaccine, all three subtypes of poliovirus will be covered.
Since March 2021, the nOPV2 vaccine has been administered to over 650 million children in 30 countries. However, despite being more genetically stable than its predecessor, it has regained virulence on four separate occasions in Nigeria and the Democratic Republic of the Congo. This highlights the fact that eradicating polio requires not only scientific advancements but also comprehensive public health initiatives to reach all children in need.
Understanding the Increase in Polio Cases
Children from under-immunized communities are particularly vulnerable to outbreaks of vaccine-derived polio. In recent years, most outbreaks have occurred in sub-Saharan Africa. However, vaccine-derived polio has also been detected in wastewater samples from the United Kingdom, Canada, Israel, and the United States, with reported cases of vaccine-derived paralytic polio in the latter two countries.
The increase in vaccine-derived polio outbreaks can be attributed to several factors. The COVID-19 pandemic has disrupted vaccination campaigns and surveillance efforts. Natural disasters and conflicts, often prevalent in polio-vulnerable countries, have further complicated the situation. Additionally, some countries chose to delay their outbreak responses, waiting for the availability of the nOPV2 vaccine instead of using the older type 2 vaccine. A model published in 2021 predicted that such delays would increase the risk of outbreaks.
Changes in the management of polio campaigns at the highest level have also contributed to the deterioration of some initiatives, according to several researchers interviewed by Nature. The Global Polio Eradication Initiative (GPEI), based in Geneva, Switzerland, has traditionally overseen the eradication efforts. However, the World Health Organization (WHO) is now leading a transition plan to transfer certain GPEI activities to national immunization and disease surveillance programs. While this integration makes long-term sense, it has faced challenges.
The Challenges of Transition
The transition process has not been without difficulties. Funding shortfalls, loss of expert staff, governance issues in some countries, and declining morale in others have been observed. A report published by the Independent Monitoring Board (IMB) in April 2022, a group of global health experts commissioned by the GPEI, criticized the transition process in certain countries.
A spokesperson from WHO acknowledged that the transition program had been prematurely implemented in some countries and stated that a more nuanced approach is being developed on a country-by-country basis, based on a more recent independent report.
A forthcoming independent report will provide further insights into the progress of the transition. It is crucial to integrate the vast resources of the GPEI into national immunization programs in the long run. However, this must be done in a manner that does not undermine the progress already achieved. The GPEI’s presence and support remain essential.
The Way Forward
In Nigeria, the announcement of the elimination of wild poliovirus in 2020 led to complacency that proved inadequate in addressing vaccine-derived polio.
Meanwhile, scientists are exploring additional tools to advance the polio eradication campaign. Efforts are underway to develop technologies that can expedite the confirmation of poliovirus presence in wastewater samples, which currently takes several weeks. Researchers, such as David Rowlands and his team at the University of Leeds, UK, are also working on developing a vaccine using virus-like particles, potentially eliminating the need for live viruses in vaccine production.
Continued research and technological advancements in vaccines are crucial to combat the rise of vaccine-derived polio. However, it is equally important to ensure that these vaccines reach the intended recipients. Highly motivated and well-funded staff, operating within programs tailored to local contexts, must be empowered to manage polio eradication efforts. The transition of polio management from the GPEI to national control should not hinder the progress towards eradication. Only then can we achieve the same success in eliminating polio as we did with smallpox.
Published in Nature.com / Translation: Graciela González
Te interesa:
Gates Foundation pledges $1.2 billion to eradicate polio Polio is reborn in the UK (and it’s not good news for the world) “God blessed me with polio”
The vaccines we lack. (Not those. The others)
How have new oral polio vaccines created using genetic engineering techniques shown promise in reducing the likelihood of outbreaks of types 1 and 3 poliovirus, and what impact could they have on polio eradication efforts
Eradicating Polio: Progress and Challenges
This content discusses the progress and challenges in eradicating polio, a highly contagious viral disease. While two out of three subtypes of the polio virus have been successfully eradicated since the launch of the eradication campaign in 1988, cases of other types of polio, including the vaccine-derived polio, remain high. Vaccine-derived polio occurs when the weakened poliovirus used in oral vaccines regains its virulence.
The article highlights a recent study published in the scientific journal Nature, which reports on the development of new oral polio vaccines designed to reduce the likelihood of outbreaks of types 1 and 3 poliovirus. These vaccines, created using genetic engineering techniques, have shown promise in animal trials and are currently undergoing human trials. If proven safe and effective, these vaccines can cover all three subtypes of poliovirus.
However, the article also emphasizes the challenges in eradicating polio, such as the occurrence of vaccine-derived polio outbreaks. Children in under-immunized communities are particularly vulnerable to these outbreaks. Factors contributing to the increase in vaccine-derived polio cases include disruptions caused by the COVID-19 pandemic, natural disasters, conflicts, and delays in outbreak responses. The article also notes changes in the management of polio campaigns at the highest level, with the World Health Organization (WHO) leading a transition plan to transfer certain activities to national immunization programs, which has faced challenges.
The transition process has encountered difficulties such as funding shortfalls, loss of expert staff, governance issues in some countries, and declining morale. The Independent Monitoring Board (IMB) criticized the implementation of the transition process in certain countries in a report published in April 2022. The WHO acknowledges the need for a more nuanced approach and is developing a country-by-country strategy for the transition.
Overall, the content highlights the progress made in polio eradication, such as the development of new vaccines, but also underscores the challenges that need to be addressed to achieve full eradication. These challenges include addressing vaccine-derived polio outbreaks and effectively managing the transition process.
These developments in oral polio vaccines are crucial in our ongoing battle against polio outbreaks. It’s inspiring to see scientists continually striving to improve and develop vaccines that can protect communities from this debilitating disease.
This is great news! The ongoing developments in oral polio vaccines will play a crucial role in combating polio outbreaks, bringing us one step closer to eradicating this debilitating disease once and for all.
2 comments
These developments in oral polio vaccines are crucial in our ongoing battle against polio outbreaks. It’s inspiring to see scientists continually striving to improve and develop vaccines that can protect communities from this debilitating disease.
This is great news! The ongoing developments in oral polio vaccines will play a crucial role in combating polio outbreaks, bringing us one step closer to eradicating this debilitating disease once and for all.