Transcript Set 8 Polio and the Polio Vaccine

Emerging Diseases
Lecture 8:
Polio
8.1: Overview
8.2: Incidence and Timeline
8.3: The Vaccine Race
Salk Vaccine
Sabin Vaccine
8.4: “Defeat” of Polio and the Age of
Optimism
8.1: Overview: Polio is an Ancient
Disease
Poliomyelitis= polio
Caused by a virus- named
poliovirus
Well-adapted to humans;
Usually causes very mild
disease
Less than 1/1000 paralytic
No other known hosts in
nature
8.2: Disease Incidence
Polio has been present since the days of ancient
Egyptians but was not a serious problem until
recently.
As North America and Western Europe clean up
their act in the late 19th and early 20th
Centuries, incidence of most infectious
diseases goes down.
But the incidence of polio goes up!????????
8.2: Polio Timeline in US
1894: First US epidemic , in Vermont: 132 cases
1916: Major outbreak nationwide: 9000 cases in
NYC alone
1934: 2500 cases in Los Angeles
1945-1949: at least 25,000 cases each year
1952: 58,000 cases
1953: 35,000 cases: “polio hysteria”-parents and
children terrified of polio
8.2: Why So Many Cases?
Disease very prevalent in human populations for
many centuries.
Historically-age of exposure to contaminated
water was very young-usually led to a mild
childhood disease only.
Sanitation produces cleaner water.
Delays age of first exposure.
Severe symptoms more frequent in older
individuals.
Vaccine for Polio?
• No cure for afflicted individuals
• May lead to permanent paralysis-total or partial
• Early attempts at vaccine in the 1930s went
terribly wrong
• Scientists did not realize there were 3 strains of
the virus in circulation
• By late 1930s National Foundation for Infantile
Paralysis/March of Dimes led the vaccine
campaign
March of Dimes
1940s-50s an effective ad campaign
Salk Vaccine
1948: Laboratory growth of poliovirus-use of cultured cells
1950’s: Vaccine “race”
1954: Large scale field trials of Salk (inactivated)
vaccine-small scale tests on Pittsburgh schoolchildren
1955: April 12-successful vaccine announced
1955: The Cutter Incident-Cutter Laboratories
produce contaminated Salk vaccine
1961: only 161 cases in US
Sabin Vaccine
1962: Sabin (attenuated) vaccine approved
aka oral polio vaccine = OPV
1964: 121 cases in US
8.4: The “Defeat” of
Polio
A folk memory in US today
Begins the “Age of Optimism”