Kid Risk, Inc., Newton, MA 02459, USA.
Public Health Rep. 2012 Jan-Feb;127(1):23-37. doi: 10.1177/003335491212700104.
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.
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.
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.
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.
美国于 1979 年消灭了本土野生脊灰病毒（WPV），并于 2000 年改用灭活脊灰病毒疫苗，这迅速结束了所有本土脊灰活病毒传播。全球范围内 WPV 的持续传播和使用允许这些病毒重新引入的可能性。我们评估了美国脊髓灰质炎暴发的风险，并探讨了暴发应对的潜在疫苗需求。
我们综合了疫苗接种率、豁免人群和人群免疫力方面的信息。我们使用感染传播模型来探索美国脊髓灰质炎暴发的潜在动态和暴发应对的潜在疫苗需求，并评估了两个不同的潜在低覆盖率亚群中人群免疫力异质性的影响。
尽管引入脊灰病毒的风险仍然存在，但鉴于常规接种率高，脊灰病毒在美广泛传播的可能性似乎不大。然而，未免疫或免疫不足的儿童群体可能会形成易感染的“窝点”，从而可能导致一个或多个麻痹性脊髓灰质炎病例。我们发现，随着联合疫苗的使用转向，使用年龄限制以及其他当前趋势（例如，免疫人群中由活脊灰病毒诱导的比例下降和疫苗豁免人群的老龄化）可能会增加脊灰病毒重新引入的脆弱性，同时应对能力可能会下降。
美国的脊灰病毒疫苗库存仍然是一个重要资源，如果活脊灰病毒传入疫苗接种率低的亚群，未来可能需要用该库存来应对暴发。
