Michael Baker, Department of Public HealthUniversity of Otago, Wellington

Late effects of polio symposium, Wellington, October 2019

Polio as a public health issue in NZ

Ian Logan and his young family in Napier in 1956, immediately prior to shifting to Fiji to take up a legal position.

His eldest daughter Jan (far right) is my wife’s mother.

Ian died in Suva from polio on 8 Sept 1958.

It's December 1936 when the first polio cases are suspected. Soon a polio epidemic is sweeping the country. Schools are closed, swimming pools and movie theatres banned to children, and travel restricted - but the epidemic is still spreading. Tom is the best runner in his school - but you can't outrun polio. Your family can't hide from it. And nobody knows where it will strike next.

Philippa Werry, 2008

Biology of polioPoliovirus• Wild Polio Virus (WPV) types 1 2 3 (type 2 eradicated since

2015) enterovirus • Vaccine-derived Poliovirus (VDPV) – from live attenuated

strain in Oral Polio Vaccine (OPV)Transmission• Person to person, mainly faecal-oral to gastrointestinal tract• WPV highly infectious with basic reproduction number ~ 6Disease • Asymptomatic in ~70-80%• Mild febrile illness with gastroenteritis & pharyngitis in ~20%• Central Nervous System (CNS) Infection causing paralytic polio with Acute

Flaccid Paralysis (AFP)• Case-fatality 2–5 % in children, 15–30 % in adults• Post-polio syndrome in 25-50% of people with paralytic polio

Polio incidence, 1915-2018Average 200 cases pa 1915-60Last local wild virus in NZ 1977

0

200

400

600

800

1000

1200

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15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61

Num

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63 66 69 72 75 78 81 84 87 90 93 96

A Polio Ward around 1952

Polio vaccination

• Available from 1956, Universal from 1959

• Inactivated Polio Vaccine (IPV, Salk) replaced live

Oral Polio Vaccine (OPV, Sabin) in 2002

• Primary course is 3 doses IPV (DTaP-IPV-HepB-

Hib) at 3, 5, 15 months

• Booster (DTaP-IPV) at 4 years

Polio eradication in Western Pacific Region

Source: WHO, Regional Office for the Western Pacific

←Pre-vaccine phase Control phase Elimination Phase

Reported Polio Cases and OPV3 coverage, WHO Western Pacific Region, 1974 – 2004Western Pacific Region certified polio-free in 2000

Future control of Polio in New Zealand

Could polio return as a public health problem in NZ?• Imported WPV - especially if resurgence eg Public Health Emergency of

International Concern, 2014, with increased spread in middle-East & Africa• Imported VDPV - from countries still using OPV eg circulating VDPV

(cVDPV) outbreak in Papua New Guinea, 2018-19• Decline in vaccine coverage – possible in post-polio eradication worldPrecautions• Continue global polio eradication goal• Maintain high IPV coverage in NZ• Ongoing surveillance, including acute flaccid paralysis (AFP)• WHO oversight:

• National Certification Committee for Eradication of Polio in NZ, • Regional Commission for the Certification of Polio Eradication in Western Pacific