Centers for Disease Control and Prevention, Atlanta GA, USA.
University of Pittsburgh, Pittsburgh PA, USA.
Clin Infect Dis. 2021 Dec 6;73(11):e4244-e4250. doi: 10.1093/cid/ciaa1884.
At the start of the 2019-2020 influenza season, concern arose that circulating B/Victoria viruses of the globally emerging clade V1A.3 were antigenically drifted from the strain included in the vaccine. Intense B/Victoria activity was followed by circulation of genetically diverse A(H1N1)pdm09 viruses that were also antigenically drifted. We measured vaccine effectiveness (VE) in the United States against illness from these emerging viruses.
We enrolled outpatients aged ≥6 months with acute respiratory illness at 5 sites. Respiratory specimens were tested for influenza by reverse-transcriptase polymerase chain reaction (RT-PCR). Using the test-negative design, we determined influenza VE by virus subtype/lineage and genetic subclades by comparing odds of vaccination in influenza cases versus test-negative controls.
Among 8845 enrollees, 2722 (31%) tested positive for influenza, including 1209 (44%) for B/Victoria and 1405 (51%) for A(H1N1)pdm09. Effectiveness against any influenza illness was 39% (95% confidence interval [CI]: 32-44), 45% (95% CI: 37-52) against B/Victoria and 30% (95% CI: 21-39) against A(H1N1)pdm09-associated illness. Vaccination offered no protection against A(H1N1)pdm09 viruses with antigenically drifted clade 6B.1A 183P-5A+156K HA genes (VE 7%; 95% CI: -14 to 23%) which predominated after January.
Vaccination provided protection against influenza illness, mainly due to infections from B/Victoria viruses. Vaccine protection against illness from A(H1N1)pdm09 was lower than historically observed effectiveness of 40%-60%, due to late-season vaccine mismatch following emergence of antigenically drifted viruses. The effect of drift on vaccine protection is not easy to predict and, even in drifted years, significant protection can be observed.
在 2019-2020 年流感季节开始时，人们担心在全球新兴 clade V1A.3 中循环的 B/Victoria 病毒与疫苗中包含的菌株发生抗原漂移。紧随强烈的 B/Victoria 活动之后，循环出现了遗传上多样化的 A(H1N1)pdm09 病毒，这些病毒也发生了抗原漂移。我们在美国测量了针对这些新兴病毒引起的疾病的疫苗有效性（VE）。
我们在 5 个地点招募了年龄≥6 个月的急性呼吸道疾病门诊患者。通过逆转录-聚合酶链反应（RT-PCR）对呼吸道标本进行流感检测。使用阴性对照设计，我们通过比较流感病例与阴性对照病例的疫苗接种几率，按病毒亚型/谱系和遗传亚群来确定流感 VE。
在 8845 名入组者中，有 2722 人（31%）的呼吸道标本检测出流感阳性，其中 1209 人（44%）为 B/Victoria，1405 人（51%）为 A(H1N1)pdm09。针对任何流感疾病的有效性为 39%（95%置信区间[CI]：32-44），针对 B/Victoria 的有效性为 45%（95% CI：37-52），针对 A(H1N1)pdm09 相关疾病的有效性为 30%（95% CI：21-39）。疫苗接种对具有抗原漂移 clade 6B.1A 183P-5A+156K HA 基因的 A(H1N1)pdm09 病毒没有保护作用（VE 7%；95% CI：-14 至 23%），这种病毒在 1 月后占主导地位。
疫苗接种为流感疾病提供了保护，主要是由于 B/Victoria 病毒引起的感染。与历史上观察到的 40%-60%的有效性相比，疫苗对 A(H1N1)pdm09 疾病的保护作用较低，这是由于出现抗原漂移病毒后，季节性后期疫苗不匹配所致。漂移对疫苗保护的影响不易预测，即使在漂移年份，也可以观察到显著的保护作用。
