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Abstract

Background:

As of 28 July 2021, 60% of adults in the United States had been fully vaccinated against COVID-19, and more than 34 million cases had been reported. Given the uncertainty regarding undocumented infections, the population level of immunity against COVID-19 in the United States remains undetermined.

Objective:

To estimate the population immunity, defined as the proportion of the population that is protected against SARS-CoV-2 infection due to prior infection or vaccination.

Design:

Statistical and simulation modeling to estimate overall and age-specific population immunity.

Setting:

United States.

Participants:

Simulated age-stratified population representing U.S. demographic characteristics.

Measurements:

The true number of SARS-CoV-2 infections in the United States was inferred from data on reported deaths using age-specific infection-fatality rates (IFRs). Taking into account the estimates for vaccine effectiveness and protection against reinfection, the overall population immunity was determined as the sum of protection levels in vaccinated persons and those who were previously infected but not vaccinated.

Results:

Using age-specific IFR estimates from the Centers for Disease Control and Prevention, it was estimated that as of 15 July 2021, 114.9 (95% credible interval [CrI], 103.2 to 127.4) million persons had been infected with SARS-CoV-2 in the United States. The mean overall population immunity was 62.0% (CrI, 58.4% to 66.4%). Adults aged 65 years or older were estimated to have the highest immunity level (77.2% [CrI, 76.2% to 78.6%]), and children younger than 12 years had the lowest immunity level (17.9% [CrI, 14.4% to 21.9%]).

Limitation:

Publicly reported deaths may underrepresent actual deaths.

Conclusion:

As of 15 July 2021, the U.S. population immunity against COVID-19 may still have been insufficient to contain the outbreaks and safely revert to prepandemic social behavior.

Primary Funding Source:

National Science Foundation, National Institutes of Health, Notsew Orm Sands Foundation, Canadian Institutes of Health Research, and Natural Sciences and Engineering Research Council of Canada.

中文翻译：

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美国对 COVID-19 的人口免疫

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抽象的

背景：

截至 2021 年 7 月 28 日，美国 60% 的成年人已完全接种了 COVID-19 疫苗，已报告超过 3400 万例病例。鉴于无证感染的不确定性，美国人口对 COVID-19 的免疫水平仍未确定。

客观的：

估计人口免疫力，定义为因先前感染或接种疫苗而免受 SARS-CoV-2 感染的人口比例。

设计：

统计和模拟建模，以估计整体和特定年龄的人群免疫力。

环境：

美国。

参与者：

代表美国人口特征的模拟年龄分层人口。

测量：

美国 SARS-CoV-2 感染的真实数量是根据使用年龄特异性感染死亡率 (IFR) 报告的死亡数据推断出来的。考虑到对疫苗有效性和防止再感染的估计，总体人口免疫力被确定为接种疫苗者和以前感染但未接种疫苗者的保护水平之和。

结果：

根据疾病控制和预防中心针对特定年龄的 IFR 估计，估计截至 2021 年 7 月 15 日，已有 114.9（95% 可信区间 [CrI]，103.2 至 127.4）百万人感染了 SARS-CoV-2在美国。平均总体人群免疫力为 62.0%（CrI，58.4% 至 66.4%）。据估计，65 岁或以上的成年人免疫水平最高（77.2% [CrI，76.2% 至 78.6%]），而 12 岁以下儿童的免疫水平最低（17.9% [CrI，14.4% 至 21.9%） ]）。

局限性：

公开报告的死亡人数可能低估了实际死亡人数。

结论：

截至 2021 年 7 月 15 日，美国民众对 COVID-19 的免疫力可能仍不足以控制疫情并安全恢复到大流行前的社会行为。

主要资金来源：

美国国家科学基金会、美国国立卫生研究院、Notsew Orm Sands 基金会、加拿大卫生研究院和加拿大自然科学与工程研究委员会。