Experts advise WHO on pandemic vaccine policies and strategies
Pandemic (H1N1) 2009 briefing note 14
30 OCTOBER 2009 | GENEVA -- The Strategic Advisory Group of Experts (SAGE) on Immunization, which advises WHO on policies and strategies for vaccines and immunization, devoted a session of its 27–29 October meeting to pandemic influenza vaccines. The experts reviewed the current epidemiological situation of the pandemic worldwide and considered issues and options from a public health perspective.
Items on the agenda included the status of vaccine availability, results from clinical trials on vaccine immunogenicity, and early results from safety monitoring in countries where administration of the H1N1 pandemic vaccine is currently under way.
The experts also advised WHO on the number of doses of vaccine needed to confer protection, also in different age groups, the co-administration of seasonal and pandemic vaccines, and vaccines for use in pregnant women. Recommendations on the formulation of seasonal influenza vaccines for the southern hemisphere in 2010 were also provided.
Current situation
Globally, teenagers and young adults continue to account for the majority of cases, with rates of hospitalization highest in very young children. Between 1% to 10% of patients with clinical illness require hospitalization. Of hospitalized patients, from 10% to 25% require admission to an intensive care unit, and from 2% to 9% have a fatal outcome.
Overall, from 7% to 10% of all hospitalized patients are pregnant women in their second or third trimester of pregnancy. Pregnant women are ten times more likely to need care in an intensive care unit when compared with the general population.
Based on these and other current findings, the experts made a number of recommendations.
Dosage
The experts noted that a variety of pandemic vaccines, including live attenuated and both adjuvanted and non-adjuvanted inactivated vaccines, have now been licensed for use by regulatory authorities. SAGE recommended the use of a single dose of vaccine in adults and adolescents, beginning at the age of 10 years, provided such use is consistent with indications from regulatory authorities.
Data on immunogenicity in children older than 6 months and younger than 10 years are limited and more studies are needed. Where national authorities have made children a priority for early vaccination, SAGE recommended that priority be given to the administration of one dose of vaccine to as many children as possible. SAGE further stressed the need for studies to determine dosage regimens effective in immunocompromised persons.
Co-administration of vaccines
Clinical trials investigating the co-administration of seasonal and pandemic vaccines are ongoing, but SAGE acknowledged the recommendation, from the US Centers for Disease Control and Prevention, that live attenuated seasonal and live attenuated pandemic vaccines should not be co-administered.
The experts recommended that seasonal and pandemic vaccines can be administered simultaneously, provided both vaccines are inactivated, or one is inactivated and the other is live attenuated. The experts found no evidence that co-administration of vaccines, as recommended, would increase the risk of adverse events.
Vaccine safety
The experts reviewed early results from the monitoring of people who have received pandemic vaccines and found no indication of unusual adverse reactions. Some adverse events following vaccination have been notified, but these are well within the range of those seen with seasonal vaccines, which have an excellent safety profile. Although early results are reassuring, monitoring for adverse events should continue.
Vaccines for pregnant women
Concerning vaccines for pregnant women, SAGE noted that studies in experimental animals using live attenuated vaccines and non-adjuvanted or adjuvanted inactivated vaccines found no evidence of direct or indirect harmful effects on fertility, pregnancy, development of the embryo or fetus, birthing, or post-natal development.
Based on these data and the substantially elevated risk for a severe outcome in pregnant women infected with the pandemic virus, SAGE recommended that any licensed vaccine can be used in pregnant women, provided no specific contraindication has been identified by the regulatory authority.
Vaccines for the southern hemisphere in 2010
SAGE also considered vaccines for use in the southern hemisphere during the 2010 winter season. Two options were assessed: a trivalent vaccine, effective against the H1N1 pandemic virus, the seasonal H3N2 virus, and influenza B viruses, and a bivalent seasonal vaccine, effective against H3N2 and influenza B viruses, which might need to be supplemented with a separate monovalent H1N1 pandemic vaccine.
The experts concluded that both options should remain available for vaccine formulations in the southern hemisphere, subject to national needs.
专家向世卫组织提出关于大流行性流感疫苗政策和战略的意见
2009年H1N1流感大流行情况说明14
2009年10月30日 | 日内瓦 -- 向世卫组织提供疫苗和免疫政策与战略方面意见的免疫战略咨询专家组（SAGE）于10月27-29日召开会议专门讨论大流行性流感疫苗问题。专家们审议了流感大流行在世界范围内当前的流行病学情况，并从公共卫生的角度考虑了各项问题和方案。
议程上的项目包括疫苗可得性的现状、疫苗免疫原性临床试验的结果以及目前正在施打H1N1大流行性流感疫苗的国家中安全监测的早期结果。
专家们还就以下问题向世卫组织提供了意见：提供保护所需的疫苗剂数（包括在不同年龄组中），合并施打季节性和大流行性流感疫苗的问题，以及用于孕妇的疫苗。还提出了关于2010年南半球季节性流感疫苗配制的建议。
目前情况
在全球，青少年和年轻成人仍然占病例的绝大多数，住院率最高的是幼儿。呈临床病症的1%至10%的病人需要住院治疗。在住院病人中，10%至25%需要接受重症监护，2%至9%导致死亡。
总体上，所有住院病人的7%至10%是中、晚期妊娠孕妇。与一般人群相比，孕妇需要接受重症监护的可能性要高10倍。
根据这些及当前的其它调查结果，专家们提出了若干建议。
剂量
专家们注意到各种大流行性流感疫苗，包括减毒活疫苗以及加入佐剂和未加佐剂的灭活疫苗，现在已由管制当局颁发使用许可证。SAGE建议成人和青少年使用单剂疫苗，起始年龄为10岁，前提是这种使用方法符合管制当局的指示。
关于年龄为6个月以上到10岁以下儿童中免疫原性的数据有限，需要开展更多的研究。在国家主管当局把儿童作为早期疫苗接种重点的地方，SAGE建议优先为尽可能多的儿童施打一剂疫苗。SAGE还强调需要开展研究，确定对免疫功能受损者有效的剂量方案。
合并施打疫苗
调查合并施打季节性和大流行性流感疫苗的临床试验正在进行，但SAGE认可美国疾病控制和预防中心的建议，即季节性流感减毒活疫苗和大流行性流感减毒活疫苗不应合并施打。
专家们建议可同时施打季节性和大流行性流感疫苗，前提是两种疫苗都是灭活的，或者一种是灭活的，另一种是减毒活疫苗。专家们未发现有证据说明按建议合并施打疫苗会加大不良事件的风险。
疫苗的安全性
专家们审议了对接受大流行性流感疫苗者进行监测的早期结果，未发现迹象说明有不同寻常的不良反应。曾有关于接种疫苗之后某些不良事件的报告，但情况决不超过接种季节性流感疫苗的情况，而后者具有极佳的安全记录。虽然早期结果令人鼓舞，但应继续监测不良事件。
供孕妇使用的疫苗
关于供孕妇使用的疫苗，SAGE注意到使用减毒活疫苗以及加入佐剂和未加佐剂的灭活疫苗对试验动物进行的研究未发现有证据说明对生育能力、妊娠、胚胎或胎儿发育、分娩或者产后发育有直接或间接的有害影响。
根据这些数据以及孕妇感染大流行性流感病毒后产生严重后果的大量加大的风险，SAGE建议任何获得许可证的疫苗都可用于孕妇，前提是管制当局未确定有任何特定禁忌。
2010年用于南半球的疫苗
SAGE 还考虑了2010年冬季期间用于南半球的疫苗。评估了两项方案：对H1N1大流行性流感病毒、H3N2季节性流感病毒和乙型流感病毒有效的一种三价疫苗， 以及对H3N2和乙型流感病毒有效的一种双价季节性流感疫苗，后者可能需要另接种一种单价H1N1大流行性流感疫苗作为补充。
专家们的结论是，根据国家需要，应保留这两种方案用于南半球的疫苗配制。
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