Pham Ba', Duval Bernard, De Serres Gaston, Gilca Vladimir, Tricco Andrea C, Ochnio Jan, Scheifele David W
BioMedical Data Sciences, GlaxoSmithKline, Ontario, Canada.
BMC Infect Dis. 2005 Jul 7;5:56. doi: 10.1186/1471-2334-5-56.
In Canada--a low endemicity country, vaccines for hepatitis A virus (HAV) are currently recommended to individuals at increased risk for infection or its complications. Applying these recommendations is difficult because the epidemiology of HAV infection is poorly defined, complex, and changing. This systematic review aimed to 1) estimate age-specific prevalence of HAV antibody in Canada and 2) evaluate infection-associated risk factors.
MEDLINE (1966-2005) and EMBASE (1980-2005) were searched to identify relevant studies for the systematic review. Archives for the Canada Diseases Weekly Report (1975-1991) and Canada Communicable Disease Report (1992-2005) were searched for relevant public health reports. Data were abstracted for study and participants' characteristics, age-specific prevalence, and risk factors.
A total of 36 reports describing 34 unique studies were included.The seroprevalence in Canadian-born children was approximately 1% in ages 8-13, 1-6% in 20-24, 10% in 25-29, 17% in 30-39, and increased subsequently. In age groups below 20 and 20-29, age-specific seroprevalence generally remained constant for studies conducted across geographic areas and over time. Compared to Canadian-born individuals, subjects born outside Canada were approximately 6 times more likely to be seropositive (relative risk: 5.7 [95% CI 3.6, 9.0]). Travel to high risk areas in individuals aged 20-39 was associated with a significant increase in anti-HAV seropositivity (RR 2.8 [1.4, 5.5]). Compared to heterosexuals, men having sex with men were only at a marginally higher risk (adjusted odds ratio 2.4 [0.9, 6.1]). High risk for seropositivity was also observed for Canadian First Nations and Inuit populations.
Results from the current systematic review show that in this low endemicity country, disease acquisition occurs in adulthood rather than childhood. The burden of disease is high; approximately 1 in 10 Canadians had been infected by ages 24-29. The increase in prevalence in young adults coincides with disease importation and increasing frequency of risk factors, most likely behavioral-related ones. Gaps in seroprevalence data were identified rendering the application of current immunization recommendations difficult. A nationwide prevalence survey for all Canadians is needed. This is essential to quantify the effectiveness of current recommendations and conduct cost-effectiveness evaluations of alternative immunization programs, if necessary.
在加拿大这个低流行率国家，目前建议甲型肝炎病毒（HAV）感染风险增加或有感染并发症风险的个体接种疫苗。由于HAV感染的流行病学定义不明确、复杂且不断变化，实施这些建议存在困难。本系统评价旨在：1）估计加拿大特定年龄的HAV抗体流行率；2）评估感染相关危险因素。
检索MEDLINE（1966 - 2005年）和EMBASE（1980 - 2005年）以确定相关研究用于系统评价。检索《加拿大疾病周报》档案（1975 - 1991年）和《加拿大传染病报告》（1992 - 2005年）以获取相关公共卫生报告。提取有关研究及参与者特征、特定年龄流行率和危险因素的数据。
共纳入36篇报告，描述了34项独特研究。在加拿大出生的儿童中，8 - 13岁的血清阳性率约为1%，20 - 24岁为1% - 6%；25 - 29岁为10%，30 - 39岁为17%，随后有所上升。在20岁以下和20 - 29岁年龄组中，跨地理区域和不同时间进行的研究中，特定年龄血清阳性率总体保持稳定。与在加拿大出生的个体相比，在加拿大境外出生的个体血清阳性的可能性大约高6倍（相对风险：5.7 [95%可信区间3.6, 9.0]）。20 - 39岁个体前往高风险地区与抗-HAV血清阳性率显著增加相关（相对风险2.8 [1.4, 5.5]）。与异性恋者相比：男同性恋者的风险仅略高（调整优势比2.4 [0.9, 6.1]）。加拿大原住民和因纽特人群中也观察到血清阳性的高风险。
本次系统评价结果表明，在这个低流行率国家，疾病感染发生在成年而非儿童期。疾病负担较高；约十分之一的加拿大人在24 - 29岁时曾被感染。年轻人中流行率的上升与疾病输入以及危险因素（最可能是与行为相关的因素）频率增加相吻合。血清阳性率数据存在差距，使得当前免疫接种建议难以实施。需要对所有加拿大人进行全国性流行率调查。这对于量化当前建议的有效性以及在必要时对替代免疫接种计划进行成本效益评估至关重要。
