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How can the virus escape from polio vaccines?

How can the virus escape from polio vaccines?

When smallpox was finally eradicated in 1980, experts hoped that the poliovirus, that is, polio, would be the next to disappear completely soon. In Hungary, for example, the polio virus broke out in 1957, but was brought under control, and the last such disease was in 1969. As a result of an eradication campaign launched in 1988, two of the three subspecies have since been eradicated virus, while the third type was trapped.

Last year, only 21 cases of wild polio were reported from Afghanistan, Pakistan and Mozambique. However, the number of cases caused by another type of polio is alarmingly high. Over the past year, 665 cases of vaccine-induced polio were recorded in 23 countries.

Vaccine-derived polio occurs when the weakened poliovirus in oral vaccines regains its potency. That is, it does not provide protection, but rather infects the little patient.

A vaccine containing a dead virus is still not perfect. Photo:

Andrew Macadam of the National Institute for Biological Standards and Control at South Mimms and colleagues in natureNew oral polio vaccine (OPV) developments have been reported that reduce the potential for vaccine-induced outbreaks of polioviruses types 1 and 3. Scientists used genetic engineering to reduce the likelihood of a weakened virus regaining its virulence. The last two vaccines were tested on mice and proven to be effective, safe and stable, so they are now being tested on humans.

Since March 2021, the so-called nOPV2 vaccine has been administered to more than 650 million children in 30 countries. Although nOPV2 is genetically more stable than its predecessor, it can still restore its virulence. This has happened four times so far, in Nigeria and the Democratic Republic of the Congo.

This is likely because eradication campaigns do not reach all children, underlining what researchers and public health officials already know: Science must go hand in hand with comprehensive public health initiatives to eradicate polio.

Why do cases multiply?

Children in immunized communities are particularly vulnerable to vaccine-derived polio. In the past few years, most outbreaks have occurred in sub-Saharan Africa. However, vaccine-derived polio has also been detected in wastewater samples in the United Kingdom, Canada, Israel and the United States – the latter two countries have also reported cases of vaccine-derived disease.

There are many reasons behind the increase in vaccine-derived polio. Just as the Covid-19 pandemic has hampered vaccination campaigns and research work, the natural disasters and conflicts that often occur in polio-prone countries have done the same. In addition, some countries have chosen to delay responses to the outbreak and wait for the nOPV2 vaccine to arrive rather than using the older type 2 vaccine.

According to many experts, changes in the management of polio campaigns also play a role in the outbreak.

The Swiss-based Global Polio Eradication Initiative (GPEI) has a long history of polio eradication, working with governments, charities and the World Health Organization (WHO). However, the World Health Organization has transferred some of the initiative’s activities to its national programs for immunization and disease surveillance. The transition wasn’t easy. Funding gaps have appeared, experts have disappeared, governance has faltered in some countries, and morale in others has plummeted. According to a report published in April 2022 by the Independent Monitoring Board (IMB), made up of health experts (which is charged with the global initiative to assess progress), this shift has been harshly criticized especially for some countries.

A new independent report from June reveals more about how transmission is progressing and says GPEI needs to stay on top of the disease.

Unfortunately, even poor wording and claims that wild poliovirus has “temporarily disappeared” or is “about to disappear” can hinder the implementation of polio campaigns in some places.

This risk is particularly present in Nigeria, where in 2020 wild poliovirus was declared eradicated. This has led to complacency in the country preventing the eradication of vaccine-induced polio.

Other tools and ideas

Meanwhile, scientists are preparing other means to advance the campaign to eradicate polio. Currently, it takes several weeks to confirm whether or not a sample of wastewater contains poliovirus. Several research groups are working on techniques to reduce this long delay.

Makadam and his colleagues are developing a form of the virus in vivo (live) will be inactive.

It is hoped that one day this will replace this highly contagious virus that is currently used in making vaccines. Scientists led by David Rowlands of the University of Leeds in Britain are developing a vaccine made of virus-like particles. If successful, live virus would not be needed to make vaccines.

It is imperative that professionals continue to research vaccines and develop technology to combat vaccine-derived polio. But the new vaccines don’t work as long as they’re still hidden in the vial. According to the authors of the article, if we want the world to see the other “face” of vaccine-derived polio, vaccine research and development must be placed in the hands of motivated and well-funded personnel who ensure fruitful results, and who participate in programs that are adapted to local conditions and do not allow polio transmission from the initiative Global Polio Eradication Report to the World Health Organization. Only in this way can polio be defeated in the same way as smallpox was once fought.

Starting from February 1, 2022, a campaign to vaccinate children against epidemic polio has been launched in Ukraine. Plans at the time were for around 10,000 children to be vaccinated during the campaign. As part of the Transcarpathia Plan, two and a half thousand children were vaccinated against the poliovirus last year.

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