MMWR Morb Mortal Wkly Rep. 2021 Aug 13;70(32):1084-1087. doi: 10.15585/mmwr.mm7032e2.
On May 5, 2021, the Colorado Department of Public Health and Environment (CDPHE) identified the first five COVID-19 cases caused by the SARS-CoV-2 B.1.617.2 (Delta) variant in Mesa County in western Colorado (population 154,933, <3% of the state population). All five initial cases were associated with school settings. Through early June, Mesa County experienced a marked increase in the proportion of Delta variant cases identified through sequencing: the 7-day proportion of sequenced specimens identified as B.1.617.2 in Mesa County more than doubled, from 43% for the week ending May 1 to 88% for the week ending June 5. As of June 6, more than one half (51%) of sequenced B.1.617.2 specimens in Colorado were from Mesa County. CDPHE assessed data from surveillance, vaccination, laboratory, and hospital sources to describe the preliminary epidemiology of the Delta variant and calculate crude vaccine effectiveness (VE). Vaccination coverage in early May in Mesa County was lower (36% of eligible residents fully vaccinated) than that in the rest of the state (44%). Compared with that in all other Colorado counties, incidence, intensive care unit (ICU) admissions, and COVID-19 case fatality ratios were significantly higher in Mesa County during the analysis period, April 27-June 6, 2021. In addition, during the same time period, the proportion of COVID-19 cases in persons who were fully vaccinated (vaccine breakthrough cases) was significantly higher in Mesa County compared with that in all other Colorado counties. Estimated crude VE against reported symptomatic infection for a 2-week period ending June 5 was 78% (95% confidence interval [CI] = 71%-84%) for Mesa County and 89% (95% CI = 88%-91%) for other Colorado counties. Vaccination is a critical strategy for preventing infection, serious illness, and death from COVID-19. Enhanced mitigation strategies, including masking in indoor settings irrespective of vaccination status, should be considered in areas with substantial or high case rates.
2021 年 5 月 5 日，科罗拉多州公共卫生与环境部（CDPHE）在科罗拉多州西部的梅萨县（人口 154933 人，占全州人口的<3%）发现了首例 5 例由 SARS-CoV-2 B.1.617.2（Delta）变异株引起的 COVID-19 病例。所有 5 例初始病例均与学校环境有关。截至 6 月初，梅萨县通过测序确定的 Delta 变异病例比例显著增加：梅萨县 7 天测序样本中 B.1.617.2 的比例从 5 月 1 日当周的 43%增加到 6 月 5 日当周的 88%。截至 6 月 6 日，科罗拉多州测序的 B.1.617.2 样本中超过一半（51%）来自梅萨县。CDPHE 评估了监测、疫苗接种、实验室和医院来源的数据，以描述 Delta 变异的初步流行病学情况并计算粗疫苗效力（VE）。5 月初，梅萨县的疫苗接种率（36%的合格居民完全接种疫苗）低于全州其他地区（44%）。与科罗拉多州其他所有县相比，在分析期内（2021 年 4 月 27 日至 6 月 6 日），梅萨县的发病率、重症监护病房（ICU）入院率和 COVID-19 病死率明显更高。此外，在同一时期，与科罗拉多州其他所有县相比，完全接种疫苗（疫苗突破病例）的 COVID-19 病例比例在梅萨县明显更高。截至 6 月 5 日的两周期间，针对报告的有症状感染的估计粗 VE 为梅萨县 78%（95%置信区间[CI] = 71%-84%），科罗拉多州其他县 89%（95% CI = 88%-91%）。疫苗接种是预防 COVID-19 感染、重症和死亡的关键策略。在病例数量较多或较高的地区，应考虑强化缓解策略，包括无论疫苗接种状况如何，在室内场所佩戴口罩。
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