New Polio Cases Linked to Oral Vaccine
Thu, April 22, 2021

New Polio Cases Linked to Oral Vaccine

Polio is a contagious illness caused by the poliovirus that usually enters the environment through the feces of someone infected / Photo by: podsy via Shutterstock

 

Polio is a contagious illness caused by the poliovirus that usually enters the environment through the feces of someone infected. In places with poor sanitation, the poliovirus can spread into the water supply, into the food supply, or by touch. A new report from the World Health Organization revealed that more new polio cases are linked to the oral vaccine instead of the poliovirus in the wild.

 

A Rare Case When Live Poliovirus Mutates Into a New Form

The report detailed four African countries, namely Angola, Central African Republic, Congo, and Nigeria, where the polio vaccine became the culprit behind the new polio cases. Instead of producing immunity and reduce the risk of illness by introducing a weakened or dead version of the disease-causing germs, the polio vaccination found by WHO mutated into an infectious form that sparked new outbreaks. This is a rare case though. The vaccine-derived polio discovered by WHO was caused by the so-called Type 2 virus present in the oral vaccine.

The report detailed four African countries, namely Angola, Central African Republic, Congo, and Nigeria, where the polio vaccine became the culprit behind the new polio cases / Photo by: Kateryna Kon via Shutterstock

 

The Mutated Form of Type 2 Virus in the Polio Vaccine

There are three wild types of poliovirus (WPV): Type 1, Type 2, and Type 3. People need to be protected against all these types of viruses to prevent polio disease and make the polio vaccination the best protection against the illness.

The Type 2 wild virus has been eradicated globally in 2015, causing the world to switch to a bivalent oral polio vaccine (OPV) instead of the trivalent OPV. With bivalent OPV, it only contains poliovirus Type 1 and Type 3. More than 95% of the population has to be immunized to eradicate the poliovirus. This is why WHO and its partners have long relied on oral polio vaccines because they can be easily administered and are cheap. It only requires two drops for every dose. Some western countries prefer the more expensive injectable polio vaccine that contains the inactivated virus, which means that it cannot cause polio.

In a report published by the British daily newspaper The Guardian, it explained that there are rare cases when the live virus in the vaccines may mutate into a new form that can then ignite new polio outbreaks.

Understanding Vaccine-Derived (cVDPV) Polio

When a child is immunized by oral polio vaccine (OPV), the weakened vaccine-virus will replicate in the intestine of the child for a limited period and it helps the person develop immunity by building up the antibodies. But the vaccine-virus is also excreted. In areas where sanitation is inadequate, the excreted vaccine-virus will spread in the immediate community. If the people there are seriously under-immunized, the excreted vaccine-virus will continue to circulate and the longer it survives, the more genetic changes it will undergo. In rare instances, the vaccine-virus may form into what is now known as the cVDPV, explained the WHO.

The Independent Monitoring Board, a statutory body set up by WHO to assess the eradication of polio, warned that the vaccine-derived poliovirus is already spreading uncontrolled in West African areas. It has likewise raised fundamental challenges and questions about the eradication process.

When a child is immunized by oral polio vaccine (OPV), the weakened vaccine-virus will replicate in the intestine of the child for a limited period and it helps the person develop immunity by building up the antibodies / Photo by: Kumar Jatinder via Shutterstock

 

Comment From a Virologist

A Columbia University virologist said, “It’s crazy because we’re vaccinating now against the vaccine in most parts of the world, not against wild polio, which is confined to Pakistan and Afghanistan.”

WHO went on to say that the solution is the same with other polio outbreaks: continue to immunize every child “several times” with the oral vaccine to stop the transmission regardless of where the virus originated. Other countries have reported vaccine-derived infection in September, such as in the Philippines, the country’s first cases of polio disease in more than 25 years.

The country’s Department of Health (DOH) Public Health undersecretary Myrna Cabotaje said via Philippine news provider Philstar that the mutated form of the Type 2 virus infected a three-year-old girl who was not vaccinated. She added that the virus strain changed overtime and acted as a naturally occurring virus.

Vaccine-Derived (cVDPV) Poliovirus: Statistics

Polio Global Eradication Initiative shared the 2019 case breakdown of cVDPV by country: Angola with 42 new cVDPV cases, Benin 6, Central African Republic 16, Chad 1, China 1, Democratic Republic of the Congo 50, Ethiopia 3, Ghana 9, Myanmar 6, Niger 1, Nigeria 18, Pakistan 11, Philippines 5, Somalia 3, Togo 3, and Zambia 1.

In DR Congo, where cases of cVDPV are high compared to other countries, the onset of paralysis started between September 22 and October 7, 2019. They also have 20 cVDPV cases in 2018. WHO added that since 2000, more than 10 million doses of OPV have already been administered to nearly 3 billion children worldwide and it helped the UN agency to prevent more than 13 million cases of polio. Furthermore, the circulating vaccine-derived poliovirus has been rapidly stopped with two to three rounds of “high-quality immunization campaigns.” There is no cure yet for the highly infectious viral disease but it can be prevented by immunization.

With the advances in medicine and healthcare spurred by new technology and knowledge, it is just unfortunate that illnesses such as polio refuse to die off because of the impoverished conditions that a lot of people still experience in the world today.