It is 2022, and I cannot believe I have to write about polio. But here we are, some parents in Israel did not vaccinate their children against polio, and they ended up catching the disease, which was so close to becoming extinct.
I am ancient, so I remember classmates in high school who were disabled from polio, probably catching the disease before vaccines became widely available. But most of you probably have not met someone in an iron lung or required braces just to walk from class to class.
The disease was so close to being extinct. dropping to around 5 cases of wild-type polio across the world in 2021. So close.
Let’s take a look at these eight cases in Israel while reminding everyone that the polio vaccine is important.
What is polio?
Polio, or poliomyelitis, is an infectious disease caused by one of three poliovirus serotypes: types 1, 2, and 3. Polioviruses are in the group of viruses called enteroviruses which usually infect the digestive tract. Polioviruses are usually transmitted through the fecal-oral or oral-oral routes.
In about 0.5 percent of symptomatic cases, the virus moves from the intestinal tract to affect the central nervous system, and muscle weakness develops resulting in flaccid paralysis.
This can develop over a few hours to a few days. The weakness most often involves the legs, but may less commonly involve the muscles of the head, neck, and diaphragm. Many people fully recover. In those with muscle weakness, about 2 – 5% of children and 15 – 30% of adults die.
There is no cure for polio; however, it is easily prevented with the polio vaccine, which is available in two forms. The first is the inactivated virus vaccine that is injected. It is based on the original vaccine developed by Jonas Salk. This version is usually known as IPV.
The second version uses a live attenuated (weakened) virus given orally. This is generally known as OPV.
The IPV vaccine is used throughout the developed world is very effective in preventing polio and has an excellent safety profile. On the other hand, the OPV version is easier to give (no syringes and needles) and easier to transport, so it is used in developing countries and areas that have warmer climates.
However, OPV has been linked to circulating vaccine-derived poliovirus (cVDPV), a very rare virus caused by the mutation or recombination of the attenuated viruses used in the oral polio vaccine. While cVDPVs are rare, they have been increasing in recent years due to low immunization rates within certain communities. cVDPV type 2 (cVDPV2) is the most prevalent, with 959 cases occurring globally in 2020.
cVDPV does not generally infect individuals who have received the vaccine.
Polio in Israel
On 29 March 2022, the Israel Ministry of Health announced that there had been eight cases of polio in the country:
- Certain polio cases of illness – 6 not vaccinated,
- Illness cases with high suspicion – 1 not vaccinated,
- A new patient undergoing testing – 1 (partially vaccinated).
Israel’s initial polio case was confirmed on March 17, 2022, when a young girl developed acute flaccid paralysis.
Further testing of the virus isolated from the girl revealed genetic links to circulating vaccine-derived poliovirus type 3 (cVDPV3) strains detected in environmental samples collected between September 2021 and January 2022 from testing sites in Jerusalem and Bethlehem.
A study published in The Lancet reported that between 2005 and 2013, Israel discontinued the administration of the live polio vaccine, deciding that it was no longer necessary. Following the confirmation of the circulating virus, the vaccine was returned to the pediatric vaccination schedule. It is unclear whether OPV or IPV will be used going forward, and I am unsure why OPV was used before.
The Global Polio Eradication Initiative (GPEI) defines polio outbreak countries as those that have stopped indigenous wild poliovirus but are experiencing re-infection either through the importation of wild or cVDPV from another country or the emergence and circulation of vaccine-derived poliovirus.
The CDC states that before any international travel, those who are unvaccinated, incompletely vaccinated, or with an unknown polio vaccination status should complete the routine polio vaccine series. The CDC also recommends that before traveling to any high-risk destination, adults who previously completed the entire routine polio vaccine series receive a single, lifetime booster dose of polio vaccine.
I want to dismiss two recurring myths about the polio vaccine:
- Both IPV and OPV are not linked to cancer. This is a myth that has been promulgated by anti-vaxxers to discredit the vaccine.
- Although the oral version of the vaccine very rarely leads to polio itself, it does not occur with the IPV, which uses a dead virus. Furthermore, cVDPV cannot infect those who have been successfully vaccinated against the virus.
Summary
Children who have not received the polio vaccine are at risk of infection from both the cVDPV and wild-type virus. Adults are at an even higher risk since the disease can cause more complications in those individuals.
It’s sad that there has been an outbreak in Israel — please, do not blame the vaccine for causing the outbreak, because seven out of the eight individuals who caught the disease were not vaccinated. This would be a non-story if not for the unvaccinated children.
We’re so close to ending polio as an endemic disease. The only way to do it is to get the vaccine (hopefully, IPV instead of OPV). Then maybe polio can go the way of smallpox, a part of our history rather than our present.
Citations
- Estivariz, Concepcion F.; Link-Gelles, Ruth; Shimabukuro, Tom (2021). “Poliomyelitis”. In Hall, Elisha; Wodi, A. Patricia; Hamborsky, Jennifer; Morelli, Valerie; Schillie, Sarah (eds.). Epidemiology and Prevention of Vaccine-Preventable Diseases (The Pink Book).
- Tulchinsky TH, Ramlawi A, Abdeen Z, Grotto I, Flahault A. Polio lessons 2013: Israel, the West Bank, and Gaza. Lancet. 2013 Nov 16;382(9905):1611-2. doi: 10.1016/S0140-6736(13)62331-4. PMID: 24238546.
