Reimagining Polio Eradication: A Breakthrough in Vaccine Development
Introduction:
Despite the success of international vaccination campaigns, the poliovirus remains a global concern, capable of causing neurological damage and paralysis in unvaccinated individuals. While wild-type polio strains have been largely eliminated, new strains can emerge from the oral polio vaccine (OPV), particularly in developing countries. In response to the ongoing threat, scientists at UCSF and the UK’s National Institute for Biological Standards and Control (NIBSC) have developed two new oral polio vaccines (nOPV) to support the World Health Organization’s efforts to eradicate polio once and for all.
The Battle Against Polio:
Polio is a debilitating disease that can cause severe disability, paralysis, or even death in children. It primarily spreads through fecal or oral particles, making it particularly problematic in regions with poor sanitation. In the early 20th century, polio outbreaks were common in the US, prompting a race to develop vaccines.
The First Effective Vaccines:
In the 1950s, the first effective vaccines against polio were introduced. The inactivated polio vaccine (IPV) and the oral polio vaccine (OPV) were administered to immunize populations, with a focus on children. IPV, made from killed poliovirus, is injected, while OPV, made from weakened poliovirus, is given as a sugar cube or candy. Today, IPV is favored in countries with advanced medical care, while OPV is used in areas where it is more accessible and affordable.
Different Vaccines, Different Challenges:
Both IPV and OPV have their advantages and challenges. People vaccinated with IPV may still become infected carriers of the polio virus, unknowingly transmitting it to the unvaccinated population. On the other hand, individuals who receive OPV shed the weakened virus they were inoculated with, potentially spreading it to unvaccinated individuals. Moreover, the weakened virus in OPV can mutate and revert to a pathogenic form, causing outbreaks of vaccine-derived polio.
Enter the nOPVs:
To address these challenges, scientists at UCSF and NIBSC have developed two new oral polio vaccines, nOPV1 and nOPV3. These vaccines are genetically engineered to significantly reduce the risk of reversion to dangerous forms of the virus. Building on the success of the first nOPV2, which received emergency use approval from the WHO in 2020, the new vaccines offer a promising solution to counter vaccine-derived polio. Clinical trials are currently underway to ensure their efficacy and safety in humans.
Closing the Gap:
Although there has been a significant reduction in polio cases over the last few decades, the last 1% of cases has proven challenging to eliminate. The presence of vaccination gaps, caused by refusal to vaccinate, natural disasters, or conflicts, enables polio to resurface in areas where it was previously eradicated. Additionally, even in regions without active polio cases, the virus can still be detected in wastewater, indicating the persisting threat.
Expanding Protection:
The development of the nOPV1 and nOPV3 vaccines represents a significant step forward in the ongoing battle against polio. By incorporating the three mutations that prevent the vaccine from becoming dangerous over time, these vaccines offer comprehensive protection against multiple poliovirus strains. However, the challenge remains to ensure widespread vaccination coverage and address the perceptions that polio has been eradicated.
Conclusion:
Polio continues to pose a threat to global health, with vaccine-derived polio cases outnumbering wild-type polio. The development of the new oral polio vaccines, nOPV1 and nOPV3, presents a promising solution to eliminate the disease once and for all. Through ongoing research, clinical trials, and effective vaccination campaigns, the world can envision a future free from polio, safeguarding the health and well-being of generations to come.
Summary:
Despite successful international immunization campaigns, the poliovirus remains a global concern, capable of causing neurological damage and paralysis in unvaccinated individuals. While wild-type polio strains have been eliminated, new strains can emerge from the oral polio vaccine (OPV), posing challenges in eradicating the disease. In response, scientists at UCSF and the NIBSC have developed two new oral polio vaccines (nOPV) to bolster the World Health Organization’s eradication efforts. These vaccines, nOPV1 and nOPV3, have been genetically engineered to minimize the risk of reversion to dangerous forms of the virus. Clinical trials are currently underway to evaluate their efficacy and safety in humans.
Additional Piece:
The quest to eradicate polio has been a long and arduous journey, filled with both success and setbacks. While significant progress has been made, the last mile is often the most challenging. The introduction of the new oral polio vaccines, nOPV1 and nOPV3, comes as a ray of hope in the battle against this debilitating disease. However, their success hinges on addressing critical factors that have hindered eradication efforts in the past.
1. Maintaining High Vaccination Coverage:
To eliminate polio once and for all, achieving and sustaining high vaccination coverage is paramount. Even in countries where polio has been eradicated, maintaining robust immunization programs is essential. This requires strong political commitment, sufficient funding, and efficient supply chains to ensure vaccines reach every child, regardless of their geographical location or socio-economic status.
2. Addressing Vaccine Hesitancy:
Vaccine hesitancy has emerged as a significant obstacle to global immunization efforts. Misinformation, mistrust, and fear surrounding vaccines have led to a decline in vaccination rates in some communities. To combat this, robust public health education campaigns are necessary, aimed at addressing vaccine misconceptions and reassuring parents about the safety and efficacy of polio vaccines. Engaging with local communities, religious leaders, and influencers can play a pivotal role in dispelling myths and fostering vaccine acceptance.
3. Strengthening Disease Surveillance:
Comprehensive disease surveillance systems are crucial for timely detection and response to any polio resurgence. This includes routine monitoring of acute flaccid paralysis (AFP) cases, as well as surveillance of sewage samples for poliovirus. By strengthening disease surveillance networks globally, health authorities can swiftly identify and contain any instances of polio transmission, preventing the disease from spreading within communities or across borders.
4. Collaboration and Partnerships:
The battle against polio requires a collaborative and multifaceted approach. Governments, international organizations, philanthropic foundations, civil society, and the private sector must work together towards a common goal. Strengthening partnerships and sharing resources, expertise, and best practices will help optimize efforts and ensure that no child is left behind.
5. Adapting to Changing Epidemiology:
As the epidemiology of polio evolves, so must our strategies. It is essential to continually reassess vaccination policies and adapt them according to the changing landscape of polio transmission. This includes closely monitoring vaccine-derived polio cases, identifying new strains, and developing targeted interventions to address emerging challenges.
Conclusion:
The development of nOPV1 and nOPV3 offers a renewed opportunity to eliminate polio once and for all. However, their success relies on the collective efforts of governments, communities, and individuals worldwide. By addressing vaccination gaps, combating vaccine hesitancy, strengthening disease surveillance, fostering collaboration, and adapting strategies, we can overcome the remaining barriers and consign polio to the annals of history. Let us seize this moment and envision a future where no child will ever suffer from this preventable disease.
Summary: As the battle against polio continues, scientists at UCSF and the NIBSC have developed two new oral polio vaccines, nOPV1 and nOPV3, to support global eradication efforts. These vaccines have been genetically engineered to minimize the risk of reversion to dangerous forms of the poliovirus. To ensure success, high vaccination coverage, addressing vaccine hesitancy, strengthening disease surveillance, fostering collaboration, and adapting strategies are key. By addressing these challenges collectively, we can achieve a polio-free world and protect future generations from this debilitating disease.
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Despite some of the most successful international vaccination campaigns in history, the poliovirus continues to circulate around the world, posing a threat of neurological damage and even paralysis for anyone who is not vaccinated.
While the original strains of polio, called wild-type, have been largely eliminated, new strains can be developed from the oral polio vaccine (OPV), which is most widely used in the developing world. Oral vaccines use live, weakened viruses that occasionally mutate into an active form, causing outbreaks even in countries thought to have eliminated polio.
Scientists at UCSF and the UK’s National Institute for Biological Standards and Control (NIBSC) have developed two new oral polio vaccines (nOPV) to bolster the World Health Organization’s latest push to finally eradicate polio. , which started two years ago using the first developed nOPV. for the same team. These are the first new polio vaccines in 50 years.
Like the first nOPV, the two newer nOPVs, which were described in Nature on June 14, they are made from weakened poliovirus that has been genetically engineered to reduce reversion to dangerous forms of the virus. Development of these new vaccines was led jointly by Raul Andino, PhD, UCSF professor of microbiology and immunology, and Andrew Macadam, PhD, NIBSC virologist.
“With such variation in vaccination within and between countries, poliovirus has persisted into the 21st century, with sometimes tragic consequences,” said Andino, co-lead author of the paper with Macadam. “We have designed these new vaccines using the lessons learned from many years of fighting polio and we believe they will help eliminate the disease once and for all.”
The evolution of the battle against polio
Polio is insidious: it is usually asymptomatic, but it can cause severe disability, paralysis or death in about one in a hundred children. It spreads via fecal or oral particles, making it particularly problematic in regions with poor sanitation. In the first half of the 20th century, polio outbreaks routinely swept across the US, leading to a race to develop vaccines.
The first effective vaccines against polio emerged in the 1950s, starting massive campaigns to immunize everyone, with an emphasis on children. The inactivated polio vaccine (IPV), made from killed poliovirus, was given by injection, while the oral polio vaccine (OPV), made from weakened poliovirus, was given as a sugar cube or candy. Today, IPV is the vaccine of choice in countries with strong medical care, and OPV, the cheapest and easiest-to-administer option, is used elsewhere.
In populations where everyone is immunized at a young age, it doesn’t matter if they receive IPV or OPV, although these vaccines act in different ways in the environment. People vaccinated with IPV can still become infected with any polio that is circulating. They won’t get sick, but they can silently transmit the virus to the unvaccinated. People vaccinated with OPV cannot silently transmit circulating polio in this way, but they can shed the weakened virus with which they were inoculated and spread it to unvaccinated people. If the weakened virus mutates, it can revert to pathogenic polio.
In populations with unvaccinated children, whether due to refusal to vaccinate, natural disaster, or war, vaccine-derived polio can spread widely, causing severe illness in an unfortunate few.
While the original, or “wild-type,” poliovirus was recently detected in Afghanistan and Pakistan, vaccine-derived polio has been detected in countries as far away as Syria, the Democratic Republic of the Congo, and the US. In fact, there have been more cases of vaccine-derived than wild-type polio in recent years, creating an urgency to counter this new source of polio.
In 2017, Andino and his colleagues discovered how OPV reverts to its harmful form: a single mutation restores the virus’s ability to migrate from the human intestine to the nervous system. Within a few years, the group devised a trio of mutations that make such a genetic reversal far less likely, and packaged it into a new vaccine.
That vaccine, nOPV2, earned the first WHO emergency use list for a vaccine in 2020 and was rapidly manufactured and distributed.
“More than 600 million doses have been delivered to more than 28 countries and, in ten cases, stopped ongoing outbreaks of vaccine-derived polio,” Andino said. “It gave us a lot more confidence that this was really working as expected.”
Covering all bases with the eradication of polio
Despite its efficacy, nOPV2 only protects against one of three strains of polio, and cases of polio have emerged recently in Israel, which is heavily vaccinated, as well as in parts of the US where people refuse to vaccinate. to his children.
Even where there are no cases of polio in hospitals, polio continues to be detected in the wastewater of major cities. There may be 99% fewer cases of polio today than 30 years ago, but the last 1% have proven difficult to eliminate.
“If there is polio somewhere, it will come back where there are vaccination gaps,” Andino said.
Andino’s group’s most recent work takes the solution they devised for nOPV2, the three mutations that usually prevent the vaccine from becoming dangerous over time, and converts it to the other two OPV types. The resulting vaccines, nOPV1 and nOPV3, effectively prevented polio in animal models. All three are much safer than the original OPVs, which can occasionally cause paralysis in those who receive the vaccine, although this is rare (on the order of one case per two million children vaccinated).
The two new vaccines are currently being tested in clinical trials to ensure they are effective and do not revert to dangerous forms in humans. Andino is hopeful that they will be incorporated in bivalent or trivalent combinations with nOPV2. Children of the future will be similarly protected from polio for life, and perhaps the world will one day experience decades of zero polio detection.
“The perception that polio is gone is dangerous,” Andino said. “For example, in India alone 500,000 children are born every week, a huge number of susceptible people. Now we have what we need to protect them.”
https://www.sciencedaily.com/releases/2023/06/230614220021.htm
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