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
1400
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
ber o
f cas
es
Year
0
1
2
3
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