Pediatric Infectious Diseases Division, Seattle Children's Hospital, Seattle, WA, USA.
Department of Pediatrics, University of Washington, Seattle, WA, USA.
Epidemiol Infect. 2021 Mar 16;149:e75. doi: 10.1017/S0950268821000571.
We investigated whether countries with higher coverage of childhood live vaccines [BCG or measles-containing-vaccine (MCV)] have reduced risk of coronavirus disease 2019 (COVID-19)-related mortality, while accounting for known systems differences between countries. In this ecological study of 140 countries using publicly available national-level data, higher vaccine coverage, representing estimated proportion of people vaccinated during the last 14 years, was associated with lower COVID-19 deaths. The associations attenuated for both vaccine variables, and MCV coverage became no longer significant once adjusted for published estimates of the Healthcare access and quality index (HAQI), a validated summary score of healthcare quality indicators. The magnitude of association between BCG coverage and COVID-19 death rate varied according to HAQI, and MCV coverage had little effect on the association between BCG and COVID-19 deaths. While there are associations between live vaccine coverage and COVID-19 outcomes, the vaccine coverage variables themselves were strongly correlated with COVID-19 testing rate, HAQI and life expectancy. This suggests that the population-level associations may be further confounded by differences in structural health systems and policies. Cluster randomised studies of booster vaccines would be ideal to evaluate the efficacy of trained immunity in preventing COVID-19 infections and mortality in vaccinated populations and on community transmission.
我们研究了儿童期常规疫苗（卡介苗或含麻疹疫苗）覆盖率较高的国家是否降低了与 2019 年冠状病毒病（COVID-19）相关的死亡率，同时考虑到各国之间已知的系统差异。在这项针对 140 个国家的基于观察的研究中，我们利用了公开的国家级数据，疫苗覆盖率更高，代表过去 14 年期间接种疫苗的人数比例，与 COVID-19 死亡人数较低有关。这两种疫苗变量的相关性都减弱了，而且一旦根据医疗保健获取和质量指数（HAQI）的公布估计值进行调整，即医疗质量指标的综合得分，麻疹疫苗覆盖率就不再具有统计学意义。BCG 覆盖率与 COVID-19 死亡率之间的关联幅度根据 HAQI 而有所不同，而 MCV 覆盖率对 BCG 与 COVID-19 死亡之间的关联几乎没有影响。虽然活疫苗覆盖率与 COVID-19 结局之间存在关联，但疫苗覆盖率变量本身与 COVID-19 检测率、HAQI 和预期寿命密切相关。这表明，人群水平的关联可能因结构性卫生系统和政策的差异而进一步受到混杂。关于加强疫苗的随机对照试验将是评估训练免疫在预防接种人群中 COVID-19 感染和死亡率以及社区传播方面的疗效的理想方法。
