Merk Hanna, Nylén Gunnar, Kühlmann-Berenzon Sharon, Linde Annika
Swedish Institute for Communicable Disease Control, 171 82 Solna, Sweden; The Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Box 281, 171 77 Stockholm, Sweden.
The National Board of Health and Welfare, 106 30 Stockholm, Sweden.
Vaccine. 2014 Dec 12;32(52):7135-40. doi: 10.1016/j.vaccine.2014.10.027. Epub 2014 Oct 28.
The evidence of increased risk of severe disease for healthy pregnant women due to inter-pandemic influenza consists mainly of observational studies of health service utilization in USA and Canada. However, these results can be context dependent and estimates in a European setting are sparse. For policy purposes we therefore decided to elucidate the potential value of vaccination in Sweden.
We conducted a retrospective, register-based study of hospitalizations due to inter-pandemic influenza or respiratory infection attributable to influenza in pregnant women in Sweden. With aggregated data from 2003 to 2009 we assessed the number needed to vaccinate (NNV) to prevent one such hospitalization.
We included on average 96,000 pregnant women/year and identified 9-48 hospitalizations/season fulfilling the case definition. Assuming 80% vaccine effectiveness the NNV was >1,900 pregnant women. The estimate is higher than those found in the USA, Canada, and UK. The difference may be explained by differing methods to estimate NNV, but also differences in propensity to hospitalize and the basic health status of the pregnant women.
Because of the increased risk associated with influenza A(H1N1)pdm09, vaccination is presently offered to all pregnant women in Sweden, but vaccination against other inter-pandemic influenza types seems disputable. The study illustrates the context dependence of preventive health measures and points to the need for national NNV estimates and international harmonization of study methods for comparisons between countries.
关于大流行间期流感导致健康孕妇患重症疾病风险增加的证据，主要来自美国和加拿大对医疗服务利用情况的观察性研究。然而，这些结果可能因背景而异，欧洲背景下的估计数据较少。因此，出于政策目的，我们决定阐明瑞典接种疫苗的潜在价值。
我们对瑞典孕妇因大流行间期流感或由流感引起的呼吸道感染而住院的情况进行了一项基于登记的回顾性研究。利用2003年至2009年的汇总数据，我们评估了预防一例此类住院所需的接种人数（NNV）。
我们平均每年纳入96,000名孕妇，每个季节确定9 - 48例符合病例定义的住院病例。假设疫苗有效性为80%，NNV大于1900名孕妇。该估计值高于在美国、加拿大和英国的发现。差异可能是由于估计NNV的方法不同，也可能是由于住院倾向和孕妇基本健康状况的差异。
由于甲型H1N1pdm09流感相关风险增加，目前瑞典向所有孕妇提供疫苗接种，但针对其他大流行间期流感类型的疫苗接种似乎存在争议。该研究说明了预防性健康措施对背景的依赖性，并指出需要进行国家NNV估计以及国际上统一研究方法以便进行国家间比较。
