Trends in the risk of U.S. polio outbreaks and poliovirus vaccine availability for response.
OBJECTIVE
The United States eliminated indigenous wild polioviruses (WPVs) in 1979 and switched to inactivated poliovirus vaccine in 2000, which quickly ended all indigenous live poliovirus transmission. Continued WPV circulation and use of oral poliovirus vaccine globally allow for the possibility of reintroduction of these viruses. We evaluated the risk of a U.S. polio outbreak and explored potential vaccine needs for outbreak response.


METHODS
We synthesized information available on vaccine coverage, exemptor populations, and population immunity. We used an infection transmission model to explore the potential dynamics of a U.S. polio outbreak and potential vaccine needs for outbreak response, and assessed the impacts of heterogeneity in population immunity for two different subpopulations with potentially low coverage.


RESULTS
Although the risk of poliovirus introduction remains real, widespread transmission of polioviruses appears unlikely in the U.S., given high routine coverage. However, clusters of un- or underimmunized children might create pockets of susceptibility that could potentially lead to one or more paralytic polio cases. We found that the shift toward combination vaccine utilization, with limited age indications for use, and other current trends (e.g., decreasing proportion of the population with immunity induced by live polioviruses and aging of vaccine exemptor populations) might increase the vulnerability to poliovirus reintroduction at the same time that the ability to respond may decrease.


CONCLUSIONS
The U.S. poliovirus vaccine stockpile remains an important resource that may potentially be needed in the future to respond to an outbreak if a live poliovirus gets imported into a subpopulation with low vaccination coverage.
Kid Risk, Inc., Newton, MA 02459, USA. kimt@kidrisk.org
Kimberly M
KM
Thompson
Gregory S
GS
Wallace
Radboud J Duintjer
RJ
Tebbens
Philip J
PJ
Smith
Albert E
AE
Barskey
Mark A
MA
Pallansch
Kathleen M
KM
Gallagher
James P
JP
Alexander
Gregory L
GL
Armstrong
Stephen L
SL
Cochi
Steven G F
SG
Wassilak
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D004196:Disease Outbreaks / Q000517:prevention & control*; D006801:Humans; D007109:Immunity / Q000276:immunology; D007223:Infant; D007231:Infant, Newborn; D008875:Middle Aged; D008954:Models, Biological; D011051:Poliomyelitis / Q000453:epidemiology* / Q000517:prevention & control / Q000635:transmission; D017955:Poliovirus / Q000472:pathogenicity*; D023321:Poliovirus Vaccines / Q000600:supply & distribution*; D012306:Risk; D014481:United States / Q000453:epidemiology; D014611:Vaccination / Q000639:trends*; D055815:Young Adult
D023321:Poliovirus Vaccines