Patient Presentation
A group of medical students were reviewing common vaccines with their preceptor. They were discussing polio and one of the students commented that he thought polio had been eradicated from the world so he wasn't sure why we still gave polio vaccine. Another student said that wasn't true as she knew there had been a recent polio outbreak in the United Kingdom. The preceptor noted that the students would see changes in their knowledge and practices over their own medical careers. "That's why it is important for you to continue to read, and learn from all kinds of good medical sources over your career. I guarantee things will change. When I started practicing we gave oral polio vaccine and I had to counsel families about the potential risk of getting polio from the vaccine and also the risks of getting wild type polio. But because of good hygiene and high vaccination rates, we transitioned to injectable polio vaccine in the United States which is a killed virus vaccine. It doesn't have the risk of contracting polio from the vaccine. I've seen the number of countries with wild polio decrease and now there's only a few countries - I think 2 or 3 now in the world with wild polio. But there's still the chance for any country to have wild type polio transmitted into the country from elsewhere and for polio to spread. You mentioned London which was polio related to the oral vaccine last year. There was also a similar outbreak in the US last year too in New York state. So that is why we continue to give polio vaccine even though it has dramatically decreased in most places in the world," she counseled.
Discussion
Poliomyelitis is caused by an enterovirus virus which causes acute flaccid paralysis. It is transmitted through fecal-oral spread. "All three serotypes of WPV [wild polio virus] are highly contagious, although 95% of primary infections cause a transient viraemia [sic] without symptoms. Paralysis occurs in one in 150 infections due to invasion of the central nervous system (CNS) and damage to the anterior horn of the spinal nerve roots." In the prevaccination era, infants and young children were most at risk. The inactivated (IPV, inactivated or Salk) vaccine and the oral (OPV, live-attenuated or Sabin) vaccines are highly effective since they were developed and deployed in 1955 and 1960 respectively. Since 1988 the World Health Organization (WHO) has worked to eradicate WPV through the Global Polio Eradication Initiative.
Learning Point
As of 2022 only two countries still have endemic WPV; those are Afghanistan and Pakistan which in 2019 had a total of 163 recorded cases. It is estimated that this global vaccination and surveillance program is preventing ~600,000 polio cases/year.
Despite this tremendously positive outcome, there still are continued threats against polio eradication. Non-polio enteroviruses have emerged which cause acute flaccid paralysis as well. This necessitates that surveillance programs continue to identify emerging organisms, monitor them and monitor for potential spread of WPV from the two endemic countries or for outbreaks of circulating vaccine-derived poliovirus (cVDPV) in outbreak countries. Per the WHO "[o]utbreak countries are those that have stopped indigenous wild poliovirus but are experiencing re-infection either through the importation of wild or vaccine-derived poliovirus from another country, or the emergence and circulation of vaccine-derived poliovirus." Currently as of June 2023, there are 35 outbreak countries. These countries (and potentially others) are at risk because of unvaccinated or under-vaccinated groups within otherwise high-immunized communities.
Outbreaks need to be treated, so how to proceed? OPV provides humoral and intestinal immunity, is easy to administer (even given house-to-house) and is inexpensive. But OPV can be inadvertently spread to unvaccinated individuals (which is good) but also risks new cVDPV emergences (which is bad). IPV provides humoral immunity but requires healthcare workers to administer and requires fixed-post locations for distribution but does not cause cVDPV emergences. SAGE or the Strategic Advisory Group of Experts on Immunization which advises the WHO currently recommends for primary and booster vaccinations in countries using OPV for patients to have 3 doses of OPV and 2 doses of IPV. Some countries which have low risk of importation and high sustained vaccine rates are using all IPV with a primary 3-dose series (with or without booster). For outbreaks, OPV is the "...best tool to quickly provide humoral and mucosal immunity to a large susceptible population." However depending the specific circumstances IPV or a combination of IPV and OPV may be used for outbreaks.
One example is the outbreak in London with sewage samples first noted in February 2022 which continued to be identified until November 2022. This outbreak was treated with a targeted extra IPV vaccine campaign for 1-9 years olds with approximately 370,000 doses given. The last cVDPV isolates were noted in November 2022. Starting in May 2023, a targeted catch-up campaign for polio and measles, mumps and rubella is ongoing in the United Kingdom.
Questions for Further Discussion
1. List some common vaccine preventable diseases?
2. For patient's traveling to or moving to other counties, where can you obtain information about their vaccine schedules?
3. How are the Centers for Disease Control and the World Health Organization similar and different from each other?
4. What is the differential diagnosis of acute paralysis?
Related Cases
To Learn More
To view pediatric review articles on this topic from the past year check PubMed.
Evidence-based medicine information on this topic can be found at SearchingPediatrics.com and the Cochrane Database of Systematic Reviews.
Information prescriptions for patients can be found at MedlinePlus for these topics: Polio and Post-Polio Syndrome and Vaccines.
To view current news articles on this topic check Google News.
To view images related to this topic check Google Images.
To view videos related to this topic check YouTube Videos.
Bao J, Thorley B, Isaacs D, et al. Polio - The old foe and new challenges: An update for clinicians. J Paediatr Child Health. 2020;56(10):1527-1532. doi:10.1111/jpc.15140
Gidengil C, Goetz MB, Newberry S, et al. Safety of vaccines used for routine immunization in the United States: An updated systematic review and meta-analysis. Vaccine. 2021;39(28):3696-3716. doi:10.1016/j.vaccine.2021.03.079
Estivariz CF, Kovacs SD, Mach M. Review of use of inactivated poliovirus vaccine in campaigns to control type 2 circulating vaccine derived poliovirus (cVDPV) outbreaks. Vaccine. 2023;41:A113-A121. doi:10.1016/j.vaccine.2022.03.027
Eurosurveillance. Lessons learnt to keep Europe polio-free: a review of outbreaks in the European Union, European Economic Area, and candidate countries, 1973 to 2013. Accessed June 26, 2023. https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2016.21.16.30210
Polio. Accessed June 27, 2023. https://www.who.int/teams/immunization-vaccines-and-biologicals/policies/position-papers/polio
Polio immunisation response in London 2022 to 2023: information for healthcare practitioners. GOV.UK. Accessed June 27, 2023. https://www.gov.uk/government/publications/inactivated-polio-vaccine-ipv-booster-information-for-healthcare-practitioners/polio-immunisation-response-in-london-2022-to-2023-information-for-healthcare-practitioners
World Health Organization. Polio vaccines: WHO Position Paper - June 2022. Weekly Epidemiological REcord, 2022, vol 97, 25. https://www.who.int/publications/i/item/WHO-WER9725-277-300
Author
Donna M. D'Alessandro, MD
Professor of Pediatrics, University of Iowa
No comments:
Post a Comment