Polio eradication

For the vaccine, see Polio vaccine.

A child receives oral polio vaccine during a 2002 campaign to immunize children in India.
Poliovirus

Polio eradication, the goal of permanent global cessation of circulation of the poliovirus and hence elimination of the poliomyelitis (polio) it causes, is the aim of a multinational public health effort begun in 1988, led by the World Health Organization (WHO), the United Nations Children's Fund (UNICEF) and the Rotary Foundation.[1] These organizations, along with the U.S. Centers for Disease Control and Prevention (CDC) and The Gates Foundation, have spearheaded the campaign through the Global Polio Eradication Initiative (GPEI). Successful eradication of infectious diseases has been achieved twice before, with smallpox in humans[2] and rinderpest in ruminants.[3]

Prevention of disease spread is accomplished by vaccination. There are two kinds of polio vaccine—oral polio vaccine (OPV), which uses weakened poliovirus, and inactivated polio vaccine (IPV), which is injected. OPV is less expensive and easier to administer, and can spread immunity beyond the person vaccinated, creating contact immunity. It has been the predominant vaccine used. However, under conditions of long-term vaccine virus circulation in under-vaccinated populations, mutations can reactivate the virus to produce a polio-inducing strain, while OPV can also, in rare circumstances, induce polio or persistent asymptomatic infection in vaccinated individuals, particularly those who are immunodeficient. IPV, being inactivated, does not carry these risks, but does not induce contact immunity. IPV is more costly and the logistics of its delivery are more challenging.

Nigeria is the latest country to have officially stopped endemic transmission of wild poliovirus, with its last reported case in 2016.[4] Of the three strains of WPV, the last recorded wild case caused by type 2 (WPV2) was in 1999, and WPV2 was declared eradicated in 2015. Type 3 (WPV3) is last known to have caused polio in 2012, and was declared eradicated in 2019.[5] All wild-virus cases since that date have been due to type 1 (WPV1).[6]

As of August 2024, Afghanistan and Pakistan are the only two countries where the disease is still classified as endemic.[7][8] Recent polio cases arise from two sources, the original "wild" poliovirus (WPV), and the much more prevalent mutated oral vaccine strains, known as circulating vaccine-derived poliovirus (cVDPV) or variant poliovirus. Vaccines against each of the three wild strains of polio have given rise to strains of cVDPV, with cVDPV2 being most prominent. cVDPV caused 524 confirmed paralytic polio cases worldwide in 2023, and was detected in 32 countries.[6]

  1. ^ "Polio Eradication". Global Health Strategies. Archived from the original on 8 March 2016. Retrieved 11 February 2016.
  2. ^ "Smallpox [Fact Sheet]". World Health Organization (WHO). Archived from the original on 3 February 2011. Retrieved 9 November 2013.
  3. ^ Ghosh P (14 October 2010). "Rinderpest virus has been wiped out, scientists say". BBC News Online. Archived from the original on 3 May 2019. Retrieved 14 October 2010.
  4. ^ Cite error: The named reference Scherbel-Ball_2020 was invoked but never defined (see the help page).
  5. ^ "GPEI-Two out of three wild poliovirus strains eradicated". Archived from the original on 7 November 2019. Retrieved 2 November 2019.
  6. ^ a b Geiger K, Stehling-Ariza T, Bigouette JP, Bennett SD, Burns CC, Quddus A, et al. (May 2024). "Progress Toward Poliomyelitis Eradication - Worldwide, January 2022-December 2023". MMWR. Morbidity and Mortality Weekly Report. 73 (19): 441–446. doi:10.15585/mmwr.mm7319a4. PMC 11115430. PMID 38753550.
  7. ^ "Endemic Countries - GPEI". Archived from the original on 22 July 2020. Retrieved 17 July 2020.
  8. ^ "Poliomyelitis (polio)". www.who.int. Archived from the original on 28 July 2020. Retrieved 28 August 2020.