Polio Eradication Flashcards
What is the IPV, how is it administered, and what are its advantages and disadvantages?
Inactivated Polio Vaccine (Salk vaccine) Killed wild type virus, Intramuscular administration No vaccine-associated disease Systemic IgG response,
Little mucosal protection (no IgA response)
More expensive than oral vaccine
What is the OPV, how is it administered, and what are its advantages and disadvantages?
Oral Polio Vaccine (Sabin vaccine) Live attenuated poliovirus Oral Administration Inexpensive Systemic immunity IgA response, good mucosal protection
Shed revertant poliovirus
Vaccine-Associated Paralytic Poliomyelitis (VAPP)
Contraindicated in immunocompromised
Source of circulating Vaccine Derived Polio Virus (Can cause polio in un-vaccinated)
Eradication
No need for ongoing polio vaccinations
Establish that eradication is a good public health strategy
Who established the March of Dimes in 1938?
Franklin Roosevelt
What kind of virus is Poliovirus?
Picornavirus
Who still receives small pox vaccinations?
US military personnel
Why is the oral polio vaccine used so widely?
Cost per dose is $0.13,
IVP is $1.50 per dose, 10x more
IPV vaccinated children may remain healthy despite being infected with poliovirus due to what?
Anti-polio IgG
Polio virus may still infect mucosal surfaces and be shed from them to infect others.
What advantage does IPV have over OPV
Does not lead to VAPP
What immune response does OPV create?
IgA
Life cycle of guinea worm
Worms escape from sores on human feet
Disgorge eggs into water supply
Larvae infect water fleas
Water fleas are injested by humans drinking the water
Larvae escape human digestive tract and grow
10-14 months later, worms emerge from sores on feet
How can guinea worm be eradicated without vaccines?
Safe drinking water
Why is eradication of poliovirus a rational goal?
Polio only infects humans
There is an effective and affordable vaccine available
Mucosal immunity prevents transmission
Virus can only survive for days or weeks outside human host
What condition is used to track the location of polio?
Most polio infections are asymptomatic. Some present as Acute Flaccid Paralysis, thus AFP is the used as a sign of possible polio infection.
Viruses other than polio may also cause AFP.
What defines polio-free certification?
2-3 years of high quality AFP surveillance without the detection of any wild type poliovirus
How many doses are used each year in polio eradication efforts?
1-2 Billion doses
At 13 cents per dose, this is ~$300 million dollars
Total costs are ~$1 billion per year, or equivalent to CUSOM budget
What viruses other than Polio cause AFP?
Coxsackie A
Coxsackie B
Enterovirus 71
ECHO viruses
Why is OPV used more frequently than IPV in
countries with wildtype poliovirus
transmission?
OPV is cheaper than IPV.
OPV induces better mucosal immunity than IPV.
Immunity from OPV stops wild type virus transmission more effectively than immunity from IPV.
OPV can be administered by almost anyone whereas IPV
requires needles & personnel who can use needles safely.
Why is the bivalent OPV more effective than the trivalent OPV in inducing protection against PV Serotype 1?
Because the OPV is live vaccine, type 1 has to compete with type 2 & 3 to infect cells. PV Serotype 1 has more attenuating mutations than type 2 and 3 and is less competitive, leading to a lower viral load and lower probability of inducing an effective immune response.
When compared to tOPV, bOPV1&3 has better efficacy
against which serotype?
Serotype 1
What does VDPV mean and how do they arise?
Vaccine Derived Polio Virus
The oral vaccine uses live viruses that have been mutated to the point that they do not cause disease in the infected person. However, these viruses continue to be shed from immunized persons for some period of time, and occasionally revert to more virulent forms. Thus, unvaccinated or immunocompromised persons may become infected and suffer the consequences of polio virus derived from the attenuated strains.
Which serotypes (1, 2, or 3) revert and cause circulating VDPV?
Serotypes 1, 2 and 3 all revert and cause cVDPV
Approximately what percent of a circulating virus’s genome will mutate each year?
1%
Thus, if a virus is 3% different from an OPV strain, it can be estimated to have circulated for 3 years.
This is all due to the error-prone viral polymerase, and most of the mutations occur at the 3rd/”wobble” position of the codon producing silent mutations.
