ATLANTA (EGMN) – Initial vaccination efforts against the novel influenza A (H1N1) should focus on immunizing as many people as possible in five target groups, while smaller subsets of some of those groups should be targeted if demand for vaccine exceeds supply. As more supply becomes available, the rest of the population should be targeted for vaccination.

Those recommendations were made by the Advisory Committee on Immunization Practices of the U.S. Centers for Disease Control and Prevention at a special 1-day meeting on July 29. Primary targets for novel influenza A (H1N1) (nH1N1) immunization efforts include the following five groups, which together total approximately 154 million individuals in the United States. Current seasonal influenza coverage among these groups is only 20%-50%, said Dr. Anthony Fiore of the CDC’s Influenza Division.

– Group 1 Pregnant women. They have been found at higher risk for complications from seasonal influenza in past pandemics, and several deaths have been reported among pregnant women during the current 2009 pandemic. Vaccination of pregnant women also is seen as a way to potentially protect infants who cannot be vaccinated, via transfer of maternal antibodies to newborns.

– Group 2 Household contacts and caregivers for children younger than 6 months of age. The aim is to provide a possible “cocooning effect,” providing indirect protection for young infants who cannot be vaccinated but are at higher risk for influenza-related complications.

– Group 3 Health care personnel and emergency medical personnel (including emergency medical technicians, firefighters, and others whose jobs involve routinely providing emergency medical care in communities). These individuals are seen as a potential source of infection for vulnerable patients. In addition, increased absenteeism could reduce the health care capacity.

– Group 4 Children and adults from 6 months through 24 years of age. Children have the highest incidence of illness, and “explosive” outbreaks in schools have been a prominent feature of the spring 2009 epidemiology of the novel influenza A (H1N1). Children younger than 5 years of age are at the highest risk for hospitalization, and are sources of infection for the community and in schools. Moreover, illness in children keeps parents home from work. Young adults also have high attack rates and are seen as vectors.

– Group 5 Adults aged 25-64 years with certain medical conditions that place them at greater risk for influenza-related complications. These include chronic pulmonary, cardiovascular, renal, hepatic, cognitive, neuromuscular, hematologic, and metabolic disorders, as well as immunosuppression caused by medications or HIV infection. About 70% of adults hospitalized thus far with nH1N1 infections had one of these conditions.

If vaccine demand exceeds availability, subgroups of the five groups should receive priority: From Group 3, health care and emergency personnel who have direct contact with patients; from Group 4, children aged 6 months through 4 years of age; and from Group 5, adults with chronic medical conditions.

When vaccine availability is sufficient at the local level to routinely vaccinate initial target populations, a decision should be made in cooperation with state and local health authorities to vaccinate healthy adults aged 25-64 years first, then individuals aged 65 years and older. The last recommendation, in contrast to seasonal influenza vaccination recommendations, reflects the fact that older individuals thus far have been at lower risk for the novel influenza A H1N1 virus.

New recommendations were needed, Dr. Fiore said, because the U.S. federal government’s 2007 pandemic vaccine priority guidance had been developed for the scenario of a severe pandemic with the potential for social disruption of critical infrastructure. The ACIP’s Influenza Working Group concluded that current epidemiologic and immunologic evidence, combined with updated information on vaccine supply and availability timelines, indicated a need to revise recommendations that had been made during prepandemic planning.

In drafting the document that ACIP voted on, the working group assumed the following: that the severity of illness and groups at higher risk for infection or complications will be similar to what has already been observed; that the safety profile and antigen content of novel H1N1 vaccines will be similar to that of seasonal vaccine; and that adequate supplies of licensed unadjuvanted vaccine can be produced for all by approximately February 2010 but that enough vaccines for all will not be available before the next pandemic wave, expected this fall.

The working group made the assumption that pandemic vaccine and seasonal vaccine availability will overlap and both will be recommended for many population groups, that two doses will be needed for protection, and that one dose will provide minimal or no protection. Initial demand for vaccination would be approximately the same as for seasonal vaccine but could increase quickly as community transmission increases, that vaccine distribution will be timely, and, finally, that “recommendation implementation will pose many challenges,” the working group’s document said.

Copyright (c) 2009 Elsevier Global Medical News. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

编者按：本版本修正了美国疫苗接种的目标人群的人数并且明确了在疫苗短缺时如何对某些亚组人群进行优先接种。

 

亚特兰大（EGMN）——针对新型甲型流感（H1N1）的初次疫苗接种应集中在为5个目标人群中尽量多的人进行接种，若疫苗需要超过供应量，应优先满足这些目标人群中少部分人的需要。随着更多疫苗的供应，应对这些人群中的其他人进行接种。

 

这些建议是由美国疾病预防控制中心（CDC）免疫接种咨询委员会（ACIP）在7月29日召开的一次特殊的单天会议上作出的。对新型甲型流感(H1N1) (nH1N1)的免疫接种主要目标包括以下5个人群，这些人群在美国的总人数为1亿5千9百万人。来自CDC流感部门的Anthony J. Fiore博士说，当前，在这些人群中，季节性流感疫苗的接种率仅为20%～50%，。

 

·         ­人群1：孕妇。人们发现，孕妇在过去的季节性流感大流行中发生并发症的风险较高，而有人报告在2009年这次流感大流行中有几例孕妇死亡。由于无法对胎儿进行接种，所以对孕妇接种亦被看作是对胎儿起潜在保护作用的一种途径，即通过母体将抗体转移至新生儿。

 

·         人群2：接触年龄小于6个月婴儿的家人和照看者。目的是带来一种可能的“保护效应”，即为无法接种却有较高流感相关并发症发生风险的婴儿提供间接保护。

 

·         人群3：卫生保健和急诊医疗人员（包括急诊医技、消防和平时在社区提供急诊医疗服务的人员）。这些人员被认为是易感人群的潜在传染源。另外，旷工增多可能削弱卫生保健的服务能力。

 

·         人群4：年龄在6个月～24岁的孩子和成人。2009年春季的新型甲型流感（H1N1）的流行病学显著特点是，孩子发病率最高和学校暴发流行。年龄小于5岁的儿童住院的风险最高，并且是社区和学校的传染源。另外，儿童患病使得父母待在家里不能去上班。青年人的发病率亦较高并被看作传染源。

 

·         人群5：年龄在25～64岁因患某些疾病而使流感相关并发症发生风险较高的成人。这些疾病包括慢性肺疾病、心血管疾病、肾病、肝病、认知障碍、神经肌肉疾病、血液病和代谢性疾病，以及因药物或HIV感染导致的免疫抑制。到目前为止，约70%的因nH1N1感染住院的成人患者患有上述疾病中的一种。

 

若疫苗需求大于供应，上述5个人群的亚群应优先供应，共4,200万人。第一亚群群——孕妇和接触年龄小于6个月婴儿的家人和照看者――仍然为优先对象。其他亚群包括：直接与患者接触的卫生保健和急诊人员；年龄在 6个月～4岁的幼儿；慢性病患儿。

 

如果当地疫苗供应充足，可常规对初始目标人群进行免疫接种，应与州和当地卫生当局配合做出首先对年龄在25～64岁的成人进行接种的决定，然后是年龄≥65岁的人群。与季节性流感接种的建议相比，上述最后建议显示至今年龄较大的成人对于新型甲型流感病毒H1N1的易感性较低。

 

Fiore博士说，新的建议是需要的，因为2007年美国联邦政府大流行性流感疫苗接种优先指导即是为有可能引起社会重要基础结构动荡的严重流感大流行而发布的。据ACIP的流感工作组总结道，目前的流行病学和免疫学证据加上疫苗供应量和时间安排，显示需要对流感大流行前计划中制定的建议进行修订。

 

在为ACIP投票起草的文件中，这个工作组作了以下估计：疾病的严重程度和感染或并发症发生风险较高的人群将与已有发现一致；新型H1N1疫苗的安全性状和抗原含量与季节性流感疫苗相似；满足全民需要的获得许可的无增效疫苗大约要到2010年2月份才能生产并充足供应，但将在这个秋季出现的下一个流感大流行浪潮来临之前并无法为全民提供足量疫苗。

 

据该工作组估计，大流行性流感疫苗和季节性流感疫苗的供应将有所重叠，并均将被建议用于某些人群，两种疫苗均需接种以期起到保护作用，仅接种一种疫苗可能仅可提供极小或无保护作用。该工作组的文件陈述，疫苗接种的最初需求将可能与季节性流感疫苗相当，但这种需求可因社区传染增多而迅速增加，疫苗将会及时分配，最终“上述建议的实施可能会带来许多挑战”。

 

爱思唯尔  版权所有