Center for Health Emergencies, Bruno Kessler Foundation, Trento, Italy.
Department of Mathematics, Computer Science and Physics, University of Udine, Udine, Italy.
Sci Rep. 2023 Apr 5;13(1):5586. doi: 10.1038/s41598-023-32501-y.
The worldwide inequitable access to vaccination claims for a re-assessment of policies that could minimize the COVID-19 burden in low-income countries. Nine months after the launch of the national vaccination program in March 2021, only 3.4% of the Ethiopian population received two doses of COVID-19 vaccine. We used a SARS-CoV-2 transmission model to estimate the level of immunity accrued before the launch of vaccination in the Southwest Shewa Zone (SWSZ) and to evaluate the impact of alternative age priority vaccination targets in a context of limited vaccine supply. The model was informed with available epidemiological evidence and detailed contact data collected across different geographical settings (urban, rural, or remote). We found that, during the first year of the pandemic, the mean proportion of critical cases occurred in SWSZ attributable to infectors under 30 years of age would range between 24.9 and 48.0%, depending on the geographical setting. During the Delta wave, the contribution of this age group in causing critical cases was estimated to increase on average to 66.7-70.6%. Our findings suggest that, when considering the vaccine product available at the time (ChAdOx1 nCoV-19; 65% efficacy against infection after 2 doses), prioritizing the elderly for vaccination remained the best strategy to minimize the disease burden caused by Delta, irrespectively of the number of available doses. Vaccination of all individuals aged ≥ 50 years would have averted 40 (95%PI: 18-60), 90 (95%PI: 61-111), and 62 (95%PI: 21-108) critical cases per 100,000 residents in urban, rural, and remote areas, respectively. Vaccination of all individuals aged ≥ 30 years would have averted an average of 86-152 critical cases per 100,000 individuals, depending on the setting considered. Despite infections among children and young adults likely caused 70% of critical cases during the Delta wave in SWSZ, most vulnerable ages should remain a key priority target for vaccination against COVID-19.
全球在疫苗接种方面存在不平等现象，这要求我们重新评估政策，以尽量减少低收入国家的 COVID-19 负担。2021 年 3 月国家疫苗接种计划启动九个月后，埃塞俄比亚只有 3.4%的人口接种了两剂 COVID-19 疫苗。我们使用 SARS-CoV-2 传播模型来估计在西南Shewa 地区（SWSZ）启动疫苗接种之前获得的免疫水平，并评估在疫苗供应有限的情况下，替代年龄优先接种目标的影响。该模型以现有的流行病学证据和在不同地理环境（城市、农村或偏远地区）收集的详细接触数据为依据。我们发现，在大流行的第一年，SWSZ 中 30 岁以下感染者导致的重症病例比例平均值将在 24.9%至 48.0%之间，具体取决于地理环境。在 Delta 波期间，据估计，该年龄段导致重症病例的比例平均增加到 66.7-70.6%。我们的研究结果表明，在考虑当时可获得的疫苗产品（ChAdOx1 nCoV-19；两剂后对感染的 65%效力）时，为老年人接种疫苗仍然是最大限度减少 Delta 造成的疾病负担的最佳策略，无论可用剂量多少。为所有≥50 岁的人接种疫苗将分别避免每 10 万人中有 40 例（95%置信区间：18-60）、90 例（95%置信区间：61-111）和 62 例（95%置信区间：21-108）重症病例，分别为城市、农村和偏远地区。为所有≥30 岁的人接种疫苗将平均避免每 10 万人中有 86-152 例重症病例，具体取决于所考虑的环境。尽管在 SWSZ 的 Delta 波期间，儿童和年轻人中的感染可能导致了 70%的重症病例，但最脆弱的年龄群体仍应成为 COVID-19 疫苗接种的重点目标。
