Polio: do vaccine viruses jeopardize polio elimination?

Polio: do vaccine viruses jeopardize polio elimination?

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Historic low of global infections - polio eradication within reach?
According to the plans of the World Health Organization (WHO), polio should have been eradicated worldwide long ago, but in recent years there have been setbacks in the fight against polio (poliomyelitis; polio for short). This year, however, a historic low is looming: So far, only 51 cases have been reported to the WHO, according to the Robert Koch Institute (RKI) announcement on World Polo Day on October 28. The RKI reports that significant progress has also been made in particularly vulnerable countries such as Afghanistan, Pakistan and Nigeria, so that there is a good chance that the disease will be eradicated by 2018.

According to the RKI, the "global police situation has never been so favorable" as it is today. Last year there were more than 350 infections. So far, only 51 diseases were reported to the WHO in 2015. The eradication (eradication) of the polioviruses seems to be within reach. However, in the "final phase of polio eradication, the swallowing vaccination, which has made the global success possible, could endanger the ultimate success", warns the RKI. This is because swallowing vaccination (OPV) with weakened but replication-capable pathogens could result in the vaccine viruses circulating in insufficiently vaccinated population groups and even causing acute flaccid paralysis.

Outbreaks from vaccine viruses
In Germany, like in other industrialized nations, only an injectable dead vaccine (IPV) has been used since 1998. However, swallow vaccination continues to be used in many poorer countries. The pathogens it contains are themselves becoming a problem. "Since 2000, 24 outbreaks worldwide with a total of 786 polio cases have been registered by so-called circulating vaccine-derived vaccine viruses (cVDPV)," reports the RKI. Also this year, 14 children from five countries (Madagascar, Nigeria, Guinea, Laos and Ukraine) had developed poliomyelitis through cVDPV. Ukraine, a country from the WHO European region, was also affected.

Strategy change by the WHO
In view of the increasing problems with pathogens caused by swallowing vaccination, the WHO has decided to change its strategy. A new strategic plan for the period 2013 to 2018 was drawn up, "the essential component of which is the global switch from OPV to IPV," reports the RK. By the end of the year, a further 120 countries should include at least one IPV dose in their routine vaccination program. However, this will trigger a significantly increasing need for appropriate vaccines, which according to the RKI can also lead to bottlenecks in vaccine supply in Germany.

Success in Pakistan and Afghanistan
In countries such as Pakistan and Afghanistan, however, not only is the difficulty with vaccine supply difficult, but vaccination workers have had to deal with much more serious problems in the past. The RKI reports that the ruling Taliban in the border area between Pakistan and Afghanistan banned vaccination against polio and accused the vaccination workers of espionage for the USA. The vaccination is an attempt to make Muslims sterile, another allegation. Their work is life-threatening for the vaccination workers there, and according to the WHO, at least 75 employees of vaccination programs have been killed in the past two and a half years.

Today, RKI reports that helpers are accompanied by armed security forces in the Taliban-controlled parts of the country and inform parents. Some religious leaders would now also support the vaccination programs. "The reduction in the number of cases in Afghanistan and Pakistan is not only important for the two countries themselves", but also to prevent the pathogens from spreading again, according to the RKI. Based on the remaining endemic areas, there have been repeated transmissions of wild polio viruses to areas that are already polio-free in the past.

Africa soon polio-free?
In the only remaining endemic country in Africa, Nigeria, the greatest success in the fight against polio was recorded this year, according to the RKI. No polio cases have occurred since July 2014 and the country was removed from the list of endemic countries a few weeks ago. As of 2012, Nigeria had more than half of all polio diseases worldwide. The last disease from a wild polio virus in Africa was "reported in August 2014 from Somalia, the country where the last smallpox disease also occurred in 1977," reports the RKI. After a further two years without a polio case, Africa could become the fifth WHO region to be certified as polio-free. In order to achieve this goal, existing vaccine gaps would have to be closed, especially in the countries affected by Ebola, because vaccination campaigns planned there had been partially suspended last year.

Critical storage of polioviruses
The so-called laboratory containment of polioviruses is also becoming increasingly important on the way to achieving polio eradication, according to the RKI. This includes all measures for safe use and storage and thus to prevent the deliberate or unwanted release of polioviruses from laboratory stocks. From the coming year, the containment will gradually be expanded to include polio vaccine viruses. In September 2015, the Global Certification Commission formally declared the type 2 polio wild virus, which has not been detected since 1999, to be exterminated. This declaration forms the basis "for the worldwide cessation of the polio vaccine against type 2 (OPV2) and the use of the bivalent polio vaccine (OPV 1 + 3) from mid-2016", reports the RKI. However, the safe storage of all type 2 polioviruses (wild and vaccine viruses) must be guaranteed beforehand.

Vaccine developed 60 years ago
The first polio vaccine was developed by Dr. Jonas Salk 60 years ago. The annual World Polo Day therefore takes place on his birthday. His vaccine was the prerequisite for the successful fight against poliomyelitis. Dr. Albert Sabin developed a second vaccine in 1961, the oral live vaccine (OPV). According to the RKI, vaccinations have led to remarkable success and 80 percent of the world's population can now live in polio-free areas. Four out of six WHO regions are polio-free. With the historic low of polio infections reached, the goal of eradication by 2018 seems quite realistic. (fp)

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Video: Polio Vaccines - Salk vs Sabin


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