Options for Poliomyelitis Vaccination in the United States Workshop Summary (1996) / Chapter Skim
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OPTIONS FOR POLIOMYELITIS VACCINATION
OPTIONS FOR POLIOMYELITIS VACCINATION
Pages 14-30
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From page 14... ...
Research on poliovirus vaccines continues, although it is unlikely that there will be major changes in oral polio vaccines because poliovirus elimination is within sight and substantial changes in vaccine formulation would require extensive and expensive evaluation to demonstrate improved safety and at least equivalent efficacy. Minor changes are being made, however.
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From page 15... ...
. Adults who are incompletely immunized against polio can receive either OPV or IPV if they are at risk of exposure to the disease, e.g.: travelers to areas where endemic poliomyelitis persists; members of communities or special population groups experiencing disease caused by wildtype poliovirus; laboratory workers handling specimens potentially contaminated with or containing poliovirus; health care Colliers in contact with patients who may be excreting poliovirus; and child-care workers in contact with vaccinated infants and young children.
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From page 16... ...
Henderson in advocacy of an OPV vaccination strategy, CDC-sponsored polio vaccine workshop, June 8, 1995. Safety The major disadvantage of OPV is the occurrence of VAPP.
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Safety testing is not only for adventitious agents but also for neurovirulent poliovirus. INACTIVATED POLIOVIRUS VACCINE ONLY6 Vaccine Characteristics Two IPV products are currently licensed in the United States.
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From page 18... ...
IPV provides some mucosal immunity and decreases poliovirus excretion. Upon challenge with OPV virus, excretion of pharyngeal OPV virus is reduced from 75 percent of individuals lacking antibody to 25 percent of those with high levels of antibody.
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From page 19... ...
, efficacy rates of 90 percent were observed with less than three doses of IPV, and Canadian authorities estimate 96 percent efficacy after three doses. In a discussion about the possible differences between the effect of the currently used enhanced-potency IPV and the older IPV on gastrointestinal immunity, in light of higher serum antibody concentrations, workshop participants noted that immunoglobulin G antibody decreases pharyngeal excretion.
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From page 20... ...
One case of VAPP was recorded in 1969, and one case of wild-type polio was reported in 1976. General Comments IPV can be combined with other parenterally administered vaccines, it is stable in adverse temperature conditions, and it has an excellent safety record.
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From page 21... ...
[A] serious question has to be asked whether you can continue to afford to have eight to ten paralytic cases of polio in the United States because of an OPV policy." From a presentation by Ronald Gold in advocacy of an IPV vaccination strategy, CDC-sponsored polio vaccine workshop, June 8, 1995.
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From page 22... ...
A study by Henry showed that 90 percent of nonimmune infants given a single dose of OPV excreted vaccine virus in their stools on day 5 postvaccination and 80 percent were still excreting the virus on day 20. In children who previously receive three or four doses of IPV, the rate of poliovirus excretion following a dose of OPV is relatively high at first, but the rate of excretion falls off fairly rapidly, along with the risk of spread of the virus that could cause contact cases of VAPP.
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From page 23... ...
All of the groups had excellent seroconversion rates and good geometric mean titers after the third dose. Three months after completing the primary series, all subjects received a single dose of OPV.
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From page 24... ...
PARENTAL CHOICE The option of allowing parents and providers to make an informed choice of which polio vaccine to administer to children was the next alternative presented. Three of the vaccine policy options that were discussed (OPV only, The material in this section is adapted from a presentation by Neal Halsey and comments by other workshop speakers or participants.
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From page 25... ...
parents and providers have a right to know the options for protecting children against polio and to participate in the decisionmaking process. Providers and parents can already make some decisions regarding which vaccines children receive, including choices among vaccines for DTP, DTaP, and Hib and scheduling choices for measles-mumps-rubella vaccination and hepatitis B vaccination.
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From page 26... ...
Full, complete, and honest information on polio disease and polio vaccine options should be provided to parents before a child is vaccinated, and the parents should be allowed to make an independent vaccination decision free from harassment from a doctor or state health official." From a presentation on parent perspectives by Kathi Williams to the CDCsponsored polio vaccine workshop, June 8, 1995. Concern was expressed that low vaccination rates among inner city populations might be made worse if those who are already somewhat skeptical about vaccination become more so when they are informed of the risks to the individual from the OPV vaccine.
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From page 27... ...
NO POLIO VACCINE 9 The final option presented was to discontinue vaccination against poliomyelitis. The risk of importation is the key factor driving continued vaccination despite eradication from a particular geographic area.
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From page 28... ...
I also respectfully suggest that the scientific evidence is compelling that the no vaccine option is the only one which will result in no cases of vaccine-associated polio and no damage to the immune and nervous systems of vaccine recipients and their contacts." From a presentation by Stephen Marini in advocacy of a no vaccine option, CDC-sponsored polio vaccine workshop, June 8, 1995. MODELING THE OPTIONS 10 The value of a model is to provide a framework for policy decisions, to clarify what is known and what is unknown, and to determine key factors in decisionmaking.
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From page 29... ...
Factors in predicting the number of contact cases of VAPP include the percentage of recipients shedding virus, the duration of excretion, the amount of virus excreted, and the characteristics of the virus excreted. Susceptible Population The key parameters in estimating the number of susceptible individuals are vaccine coverage and rate of exposure to vaccine virus.
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From page 30... ...
Questions with respect to predicting the number of susceptible individuals also remain: . How would immunization coverage rates change with a more complicated schedule?
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