Institute of Vaccines and Medical Biologicals (IVAC), Nha Trang, Vietnam.
Tay Nguyen Institute of Hygiene and Epidemiology, Buon Me Thuot, Vietnam.
Epidemiol Health. 2021;43:e2021076. doi: 10.4178/epih.e2021076. Epub 2021 Oct 6.
An A/H5N1 vaccine (IVACFLU-A/H5N1) was accepted for use in Vietnam; however, antibody persistence after vaccination has not been well characterized. We examined post-vaccination antibody persistence and related risk factors in individuals enrolled in the phase II IVACFLU-A/ H5N1 vaccine trial in Ninh Hoa, Vietnam, who received a 15-μg dose (2 injections 21 days apart).
We used a longitudinal study design to follow 86 participants, without a control group. The participants tested as anti-A/H5N1 immunoglobulin G seronegative at baseline and received both doses of the vaccine. Blood was drawn at 30 months and 36 months after the complete vaccination to assess antibody status. Antibody persistence status was compared by demographic characteristics and exposure risk factors using univariate logistic regression.
In total, 84.9% and 52.3% of the population showed persistence of at least 1/10 of the A/H5N1 antibodies at 30 months and 36 months after IVACFLU-A/H5N1 vaccination, respectively. The odds of antibody persistence were higher in older people, but lower in people who had experienced flu-like symptoms in the past 18 months or between 2 visits. We recorded no differences between A/H5N1 antibody persistence and exposure risk factors, including having a poultry farm, coming into contact with poultry, and slaughtering and processing poultry.
This study demonstrated noteworthy antibody persistence, indicated by the seroconversion rate and geometric mean titer at 30 months and 36 months after the IVACFLU-A/H5N1 vaccine. Further studies should investigate older people and those who experienced flu-like symptoms to determine a suitable time for a booster shot.
越南批准使用 A/H5N1 疫苗（IVACFLU-A/H5N1）；然而，疫苗接种后的抗体持久性尚未得到很好的描述。我们研究了在越南宁和进行的 IVACFLU-A/H5N1 疫苗 II 期试验中接种疫苗的个体的接种后抗体持久性及其相关的危险因素，这些个体接受了 15μg 剂量（21 天内注射 2 次）。
我们使用纵向研究设计对 86 名参与者进行了随访，没有对照组。这些参与者在基线时抗 A/H5N1 免疫球蛋白 G 血清学阴性，并接受了两剂疫苗。在完全接种疫苗后 30 个月和 36 个月抽取血液以评估抗体状态。使用单变量逻辑回归比较了人口统计学特征和暴露危险因素的抗体持久性状况。
总共有 84.9%和 52.3%的人群在接种 IVACFLU-A/H5N1 疫苗后 30 个月和 36 个月时分别至少保持了 1/10 的 A/H5N1 抗体。在老年人中，抗体持久性的可能性更高，但在过去 18 个月或两次就诊期间经历过流感样症状的人群中则较低。我们未记录到 A/H5N1 抗体持久性与暴露危险因素之间存在差异，包括有家禽养殖场、接触家禽以及宰杀和加工家禽。
这项研究表明，在接种 IVACFLU-A/H5N1 疫苗后 30 个月和 36 个月时，血清转化率和几何平均滴度均表明存在显著的抗体持久性。进一步的研究应该调查老年人和经历过流感样症状的人群，以确定适当的加强针时间。
