ワクチン未接種者は入院する確率が29倍高い

ワクチン2回接種者に比べて、ワクチン未接種者の感染率は4.9倍、入院率は29.2倍。

入院率や重篤率が3倍以下しか違わないように見えるかもしれないが、これはワクチン接種者がかなり高齢者に偏っていて、元々重篤になり易い人に接種しているからである。

同等の母集団のように年齢調整すると、29倍違うのである。

（2021/08/25 管理者記載）

*******************************************************

2021年5月1日から7月25日までの間に、カリフォルニア州ロサンゼルス郡の住民における43,127件のSARS-CoV-2感染のうち、10,895人（25.3％）が完全ワクチン接種者、1,431人（3.3％）が1回のみのワクチン接種者、30,801人でした。 （71.4％）はワクチン未接種者でした。 7月25日時点でワクチン2回接種者に比べて、ワクチン未接種者の感染率は4.9倍、入院率は29.2倍でした。

デルタバリアントが優勢だった7月、PCRサイクルの閾値は、ワクチン未接種者、部分ワクチン接種者、完全ワクチン接種者で同様でした。

ワクチン接種後の感染を調べるために、ロサンゼルス郡公衆衛生局（LACDPH）は、COVID-19サーベイランスとCalifornia Immunization Registry 2（CAIR2）データを使用して、ワクチン接種による2021年5月1日から7月25日の年齢調整感染率と入院率を調べました。

ヌクレオカプシド（N）を含む2つのSARS-CoV-2遺伝子標的の定性的逆転写ポリメラーゼ連鎖反応（RT-PCR）からの全ゲノム配列決定（WGS）ベースのSARS-CoV-2系統およびサイクル閾値（Ct）値検体のサンプルとして、タンパク質遺伝子領域とオープンリーディングフレーム1 ab（ORF1ab）ポリタンパク質遺伝子領域が報告されました。

16歳以上のロサンゼルス郡居住者で報告された43,127件のSARS-CoV-2感染のうち、10,895人（25.3％）は完全ワクチン接種者、1,431人（3.3％）は1回のみのワクチン接種者、30,801人（71.4％）はワクチン未接種者でした。

SARS-CoV-2に感染した完全ワクチン接種者のうち入院した人は3.2%、ICUに入院した人は0.5%、人工呼吸を受けた人は0.2%、

部分ワクチン接種者では入院6.2％、ICU1.0％、人工呼吸器0.3％、

ワクチン未接種者では入院7.6％、ICU1.5％、人工呼吸器0.5％でした。（すべての比較でp <0.001）。

7月25日、ワクチン未接種者のSARS-CoV-2感染率は4.9倍、入院率は完全ワクチン接種者の29.2倍でした。

5月1日から7月25日の間に、系統データを含む6,752サンプルから推定されたB.1.617.2（Delta）バリアント感染の割合は、完全ワクチン接種者で8.6％→91.2％、部分ワクチン接種者で0％→88.1％、およびワクチン未接種者で8.2％→87.1％と増加しました。 5月には、ワクチン接種状況によってCt値の中央値に差がありました。しかし、7月までに、遺伝子標的による完全ワクチン接種者、部分ワクチン接種者、および非ワクチン接種者の検体間で差異は検出されませんでした。これらの感染率と入院率のデータは、ワクチンが、デルタ変異体の感染が増加していた期間中、SARS-CoV-2感染と重症COVID-19に対して防御的であったことを示しています。他の予防戦略と連携して、COVID-19ワクチン接種を増やす努力は、COVID-19関連の入院と死亡を防ぐために重要です。

LACDPHは、2021年5月1日から7月25日に試験所からLACDPHに報告されたSARS-CoV-2の実験室で確認された症例のデータを分析しました。これには、合計9,651,332人のロサンゼルス郡の住民（パサデナとロングビーチの住民を除く）が含まれます。

検査室で確認されたSARS-CoV-2感染は、呼吸器検体中のSARS-CoV-2RNAまたは抗原の最初の検出として定義されました。ワクチン接種状況は、決定論的パスと確率論的パスの両方を備えたアルゴリズムを使用して、SARS-CoV-2症例サーベイランスと個人レベルの識別子のCAIR2データを照合することによって確認されました。 2回接種シリーズ（Pfizer-BioNTechまたはModerna COVID-19ワクチン）の2回目の接種から14日以上後、または1回接種のJanssen（Johnson＆Johnson）COVID-19ワクチンの1回接種後、完全にワクチン接種されたと見なされました。 2回投与シリーズで最初の投与を受けてから14日以上後および2回目の投与から14日以内に部分的にワクチン接種された。2回接種シリーズの初回投与または1回接種ワクチンの接種後14日以内、またはCAIR2ワクチン接種データが入手できなかった場合はワクチン未接種。 COVID-19に関連する入院は、最初のSARS-CoV-2感染から14日以内に発生した入院と定義されました。 COVID-19に関連する死亡は、最初の検査室で確認されたSARS-CoV-2感染の日から60日以内に発生する死亡、またはCOVID-19が死亡の原因または原因として記載されている死亡として定義されました。

ワクチン接種状況による感染率の差は、カテゴリー変数のカイ二乗検定と中央値のクラスカル・ウォリス検定を使用して計算されました。 0.05未満のp値は統計的に有意であると見なされました。年齢調整されたローリング7日間のSARS-CoV-2感染率と入院率は、ワクチン接種状況によって推定されました。サンプルの利用可能なすべてのシーケンス結果からのWGS系統データ（6,752）および診断定性的RT-PCRからのCt値2つの研究所からの2つの遺伝子（SARS-CoV-2ヌクレオカプシド[SC2N; 5,179]、ORF1ab [1,041]、およびN [1,062]）を標的とするアッセイが、ワクチン接種状況によって経時的に報告されました。分析は、SAS（バージョン9.4; SAS Institute）を使用して実施されました。この活動は、LACDPHのInstitutional Review Board（IRB）によって、公衆衛生業務に必要な監視活動であると判断されたため、IRBレビューは必要ありませんでした。

ロサンゼルス郡の住民の完全接種者の割合は、2021年5月1日の27％から2021年7月25日の51％に増加しました。同じ期間に、16歳以上の住民のSARS-CoV-2感染の43,127例が報告されました。 LACDPHに対して、完全ワクチン接種者の10,895（25.3％）、部分ワクチン接種者の1,431（3.3％）、および非ワクチン接種者の30,801（71.4％）を含む。

すべてのグループで症例の最大の割合は、30〜49歳と18〜29歳の成人、女性、およびヒスパニック系の人々でした。 7月25日に完全にワクチン接種された人のうち、55.2％がPfizer-BioNTechワクチンを接種し、28.0％がModernaワクチンを接種し、16.8％がJanssen ワクチンを接種しました。

完全ワクチン接種者のうち入院した人は3.2%、ICUに入院した人は0.5%、人工呼吸を受けた人は0.2%、

部分ワクチン接種者では入院6.2％、ICU1.0％、人工呼吸器0.3％、

ワクチン未接種者では入院7.6％、ICU1.5％、人工呼吸器0.5％でした。（p <0.001）。

入院した人と集中治療室に入院した人の中では、年齢の中央値はワクチン接種者の方が高かった。

ワクチン接種者（中央値= 64歳、四分位範囲[IQR] = 53.0〜76.0歳、中央値= 64歳、IQR = 54.0〜76.0歳）、

部分的ワクチン接種者（中央値= 59、IQR = 46.0–72.0;中央値= 65、IQR = 57.0–80.0）、

ワクチン未接種者（中央値= 49、IQR = 35.0–62.0;中央値= 56、IQR = 41.0–66.0）であった（p <0.001）。

完全ワクチン接種者（1.2％）と部分的ワクチン接種者（2.0％）は、ワクチン未接種者（4.2％）と比較して、SARS-CoV-2陽性検査結果判明後に入院しました。

完全ワクチン接種を受けた人の死亡率は0.2%（24人）、部分ワクチン接種者で0.5％（7人）、ワクチン未接種者で0.6％（176人）とより低かった（p <0.001）。

死亡調査では、完全ワクチン接種者24人のうち6人が、HIV感染、癌（すなわち、前立腺、膵臓、肺、または白血病）、肝移植などの免疫不全状態にあった。

年齢の中央値は完全ワクチン接種者（中央値= 78歳、IQR = 63。5〜87。5年）、部分的ワクチン接種者（中央値= 74、IQR = 58.0〜80.0）、ワクチン未接種者（中央値= 63、IQR = 51.5〜79.5）と、ワクチン接種者の方が高かった（p = 0.01）。

ロサンゼルス郡の全居住者の中で、年齢調整された7日間の発生率と入院率は、ワクチン未接種、完全ワクチン接種、および部分ワクチン接種の人の間で指数関数的に増加し、6月下旬にワクチン未接種の人の間で最も高い率でした（図1）。 5月1日、ワクチン未接種者の年齢調整発生率（人口10万人あたり35.2）は8.4倍、年齢調整入院率（人口10万人あたり4.6）は完全ワクチン接種者の10.0倍（それぞれ4.2および0.46）でした。

部分的ワクチン接種者は、完全ワクチン接種者と同様の発生率（4.1）と入院率（0.27）でした。

7月25日、ワクチン未接種者（315.1）の年齢調整発生率は、完全ワクチン接種者（63.8）の4.9倍でした。部分的にワクチン接種された人の割合は46.8でした。

ワクチン未接種者の年齢調整入院率（29.4）は、完全ワクチン接種者の29.2倍（1.0）でした。

入院率は部分的にワクチン接種された人で同様でした（0.90）

（補足表; https：//stacks.cdc.gov/view/cdc/109087）

5月1日から7月25日までの間に、SARS-CoV-2デルタ変異型感染症の16歳以上の居住者の割合は、完全ワクチン接種者の8.6％から91.2％（1,667）に、部分ワクチン接種者の0％から88.1％に増加しました（ 198）、ワクチン未接種者では8.2％から87.1％（4,887）（図2）。

5月のCt値の中央値は、ORF1ab遺伝子標的でそれぞれ22.8、36.6、および27.7）およびN遺伝子標的でそれぞれ24.0、36.0、および30.6でした。ただし7月には遺伝子ターゲット間でワクチン接種状況による違いは見つかりませんでした（SC2N = 19.3、20.2、および19.4; ORF1ab = 18.8、17.8、および19.0; N = 19.3、18.6、および19.5）。

SARS-CoV-2 Infections and Hospitalizations Among Persons Aged ≥16 Years, by Vaccination Status — Los Angeles County, California, May 1–July 25, 2021

Early Release / August 24, 2021 / 70

Jennifer B. Griffin, PhD; Meredith Haddix, MPH; Phoebe Danza, MPH; Rebecca Fisher, MPH; Tae Hee Koo, MPH; Elizabeth Traub, MPH; Prabhu Gounder, MD; Claire Jarashow, PhD; Sharon Balter, MD

https://www.cdc.gov/mmwr/volumes/70/wr/mm7034e5.htm?s_cid=mm7034e5_x

Summary

What is already known about this topic?

Although COVID-19 vaccines are highly effective, some fully vaccinated persons will be infected with SARS-CoV-2.

What is added by this report?

During May 1–July 25, 2021, among 43,127 SARS-CoV-2 infections in residents of Los Angeles County, California, 10,895 (25.3%) were in fully vaccinated persons, 1,431 (3.3%) were in partially vaccinated persons, and 30,801 (71.4%) were in unvaccinated persons. On July 25, infection and hospitalization rates among unvaccinated persons were 4.9 and 29.2 times, respectively, those in fully vaccinated persons. In July, when the Delta variant was predominant, cycle threshold values were similar for unvaccinated, partially vaccinated, and vaccinated persons.

What are the implications for public health practice?

Efforts to enhance COVID-19 vaccination coverage, in coordination with other prevention strategies, are critical to preventing COVID-19–related hospitalizations and deaths.

COVID-19 vaccines fully approved or currently authorized for use through Emergency Use Authorization from the Food and Drug Administration are critical tools for controlling the COVID-19 pandemic; however, even with highly effective vaccines, a proportion of fully vaccinated persons will become infected with SARS-CoV-2, the virus that causes COVID-19 (1). To characterize postvaccination infections, the Los Angeles County Department of Public Health (LACDPH) used COVID-19 surveillance and California Immunization Registry 2 (CAIR2) data to describe age-adjusted infection and hospitalization rates during May 1–July 25, 2021, by vaccination status. Whole genome sequencing (WGS)–based SARS-CoV-2 lineages and cycle threshold (Ct) values from qualitative reverse transcription–polymerase chain reaction (RT-PCR) for two SARS-CoV-2 gene targets, including the nucleocapsid (N) protein gene region and the open reading frame 1 ab (ORF1ab) polyprotein gene region,* were reported for a convenience sample of specimens. Among 43,127 reported SARS-CoV-2 infections in Los Angeles County residents aged ≥16 years, 10,895 (25.3%) were in fully vaccinated persons, 1,431 (3.3%) were in partially vaccinated persons, and 30,801 (71.4%) were in unvaccinated persons. Much lower percentages of fully vaccinated persons infected with SARS-CoV-2 were hospitalized (3.2%), were admitted to an intensive care unit (0.5%), and required mechanical ventilation (0.2%) compared with partially vaccinated persons (6.2%, 1.0%, and 0.3%, respectively) and unvaccinated persons (7.6%, 1.5%, and 0.5%, respectively) (p<0.001 for all comparisons). On July 25, the SARS-CoV-2 infection rate among unvaccinated persons was 4.9 times and the hospitalization rate was 29.2 times the rates among fully vaccinated persons. During May 1–July 25, the percentages of B.1.617.2 (Delta) variant infections estimated from 6,752 samples with lineage data increased among fully vaccinated persons (from 8.6% to 91.2%), partially vaccinated persons (from 0% to 88.1%), and unvaccinated persons (from 8.2% to 87.1%). In May, there were differences in median Ct values by vaccination status; however, by July, no differences were detected among specimens from fully vaccinated, partially vaccinated, and unvaccinated persons by gene targets. These infection and hospitalization rate data indicate that authorized vaccines were protective against SARS-CoV-2 infection and severe COVID-19 during a period when transmission of the Delta variant was increasing. Efforts to increase COVID-19 vaccination, in coordination with other prevention strategies, are critical to preventing COVID-19–related hospitalizations and deaths.

LACDPH analyzed data for laboratory-confirmed cases of SARS-CoV-2 reported from testing laboratories to LACDPH during May 1–July 25, 2021, which included a total of 9,651,332 Los Angeles County residents (excluding Pasadena and Long Beach residents).† A laboratory-confirmed SARS-CoV-2 infection was defined as a first detection§ of SARS-CoV-2 RNA or antigen in a respiratory specimen. Vaccination status was ascertained by matching SARS-CoV-2 case surveillance and CAIR2 data on person-level identifiers using an algorithm with both deterministic and probabilistic passes. Persons were considered fully vaccinated ≥14 days after receipt of the second dose in a 2-dose series (Pfizer-BioNTech or Moderna COVID-19 vaccines) or after 1 dose of the single-dose Janssen (Johnson & Johnson) COVID-19 vaccine¶; partially vaccinated ≥14 days after receipt of the first dose and <14 days after the second dose in a 2-dose series; and unvaccinated <14 days after receipt of the first dose of a 2-dose series or 1 dose of the single-dose vaccine or if no CAIR2 vaccination data were available. COVID-19–associated hospitalizations were defined as hospital admissions occurring ≤14 days after a first SARS-CoV-2 infection. COVID-19–associated deaths were defined as deaths occurring ≤60 days after the date of a first laboratory-confirmed SARS-CoV-2 infection or deaths with COVID-19 listed as a cause of or contributing condition to death.

Differences in the percentages of infections by vaccination status were calculated using chi-square tests for categorical variables and Kruskal-Wallis tests for medians; p-values <0.05 were considered statistically significant. Age-adjusted rolling 7-day SARS-CoV-2 infection and hospitalization rates were estimated by vaccination status.** Using convenience samples, WGS lineage data from all available sequencing results (6,752)†† and Ct values from diagnostic qualitative RT-PCR assays targeting two genes (SARS-CoV-2 nucleocapsid [SC2N; 5,179], ORF1ab [1,041], and N [1,062]) from two laboratories were reported over time by vaccination status. Analyses were conducted using SAS (version 9.4; SAS Institute). This activity was determined by LACDPH’s Institutional Review Board (IRB) to be a surveillance activity necessary for public health work and therefore did not require IRB review.

The percentage of fully vaccinated Los Angeles County residents increased from 27% on May 1, 2021, to 51% on July 25, 2021. During the same period, 43,127 cases of SARS-CoV-2 infection among residents aged ≥16 years were reported to LACDPH, including 10,895 (25.3%) in fully vaccinated persons, 1,431 (3.3%) in partially vaccinated persons, and 30,801 (71.4%) in unvaccinated persons (Table). The largest percentages of cases across all groups were among adults aged 30–49 years and 18–29 years, females, and Hispanic persons. Among fully vaccinated persons on July 25, 55.2% had received the Pfizer-BioNTech vaccine, 28.0% had received the Moderna vaccine, and 16.8% had received the Janssen vaccine. Lower percentages of fully vaccinated persons were hospitalized (3.2%), were admitted to an intensive care unit (0.5%), and required mechanical ventilation (0.2%) compared with partially vaccinated persons (6.2%, 1.0%, and 0.3%, respectively) and unvaccinated persons (7.6%, 1.5%, and 0.5%, respectively) (p<0.001). Among hospitalized persons and persons admitted to an intensive care unit, the median age was higher among vaccinated persons (median = 64 years, interquartile range [IQR] = 53.0–76.0 years; median = 64 years, IQR = 54.0–76.0 years, respectively) and partially vaccinated persons (median = 59, IQR = 46.0–72.0; median = 65, IQR = 57.0–80.0, respectively) than among unvaccinated persons (median = 49, IQR = 35.0–62.0; median = 56, IQR = 41.0–66.0, respectively) (p<0.001). A lower percentage of fully vaccinated (1.2%) and partially vaccinated (2.0%) persons were admitted to a hospital after their SARS-CoV-2 positive test result date compared with unvaccinated persons (4.2%). A lower percentage of deaths (0.2%, 24) occurred among fully vaccinated persons than among partially vaccinated (0.5%, seven) and unvaccinated (0.6%, 176) persons (p<0.001). Death investigations determined that six of the 24 fully vaccinated persons who died had immunocompromising conditions, including HIV infection, cancer (i.e., prostate, pancreatic, lung, or leukemia), and liver transplantation, and that the median age was higher among vaccinated (median = 78 years, IQR = 63.5–87.5 years) and partially vaccinated (median = 74, IQR = 58.0–80.0) persons than among unvaccinated persons (median = 63, IQR = 51.5–79.5) (p = 0.01).

Among all Los Angeles County residents, the age-adjusted 7-day incidence and hospitalization rates increased exponentially among unvaccinated, fully vaccinated, and partially vaccinated persons, with the highest rates among unvaccinated persons in late June (Figure 1). On May 1, in unvaccinated persons, the age-adjusted incidence (35.2 per 100,000 population) was 8.4 times and the age-adjusted hospitalization rate (4.6 per 100,000 population) was 10.0 times the rates in fully vaccinated persons (4.2 and 0.46, respectively). Partially vaccinated persons had a similar incidence (4.1) and hospitalization rate (0.27) as fully vaccinated persons. On July 25, the age-adjusted incidence in unvaccinated persons (315.1) was 4.9 times that in fully vaccinated persons (63.8); the rate among partially vaccinated persons was 46.8. The age-adjusted hospitalization rate in unvaccinated persons (29.4) was 29.2 times the rate in fully vaccinated persons (1.0); the hospitalization rate was similar in partially vaccinated persons (0.90) (Supplementary Table; https://stacks.cdc.gov/view/cdc/109087).

During May 1–July 25, the percentages of residents aged ≥16 years with SARS-CoV-2 Delta variant infections increased from 8.6% to 91.2% in fully vaccinated persons (1,667), from 0% to 88.1% in partially vaccinated persons (198), and from 8.2% to 87.1% in unvaccinated persons (4,887) (Figure 2). In May, median Ct values were lower in specimens from unvaccinated persons than in those from partially vaccinated and fully vaccinated persons for the ORF1ab gene target (22.8, 36.6, and 27.7, respectively) and N gene target (24.0, 36.0, and 30.6, respectively); however, in July, no differences were found by vaccination status among the gene targets (SC2N = 19.3, 20.2, and 19.4; ORF1ab = 18.8, 17.8, and 19.0; N = 19.3, 18.6, and 19.5, respectively) (Figure 2).

Discussion

The results of this population-based analysis using linked SARS-CoV-2 infection surveillance and vaccination registry data indicate that fully vaccinated persons aged ≥16 years with SARS-CoV-2 infection were less likely than unvaccinated persons to be hospitalized, to be admitted to an intensive care unit, to require mechanical ventilation, or to die from SARS-CoV-2 infection during a period when the Delta variant became predominant. Although age-adjusted hospitalization rates in partially vaccinated persons were similar to those in fully vaccinated persons, age-adjusted incidences were slightly lower in partially vaccinated persons than in fully vaccinated persons. These data indicate that authorized vaccines protect against SARS-CoV-2 infection and severe COVID-19, even with increased community transmission of the newly predominant Delta variant (2).

The SARS-CoV-2 Delta variant is highly transmissible (3) and became the predominant variant in Los Angeles County during May–July 2021. During this period, SARS-CoV-2 cases and hospitalizations increased substantially, most notably among unvaccinated persons. In May, specimens from fully vaccinated and partially vaccinated persons had higher Ct values for two gene targets compared with unvaccinated persons; however, by July, median Ct values had decreased and were similar in all gene regions in specimens from fully vaccinated, partially vaccinated, and unvaccinated persons. These findings are similar to those from a recent study showing no difference in Ct values in specimens from vaccinated and unvaccinated persons during a large outbreak (4). Ct values are correlated with the amount of viral nucleic acid present; however, Ct values are an imperfect proxy for viral nucleic acid load, are not standardized across testing platforms, vary by specimen type and time from specimen collection, and should be limited to assessing differences at the population level, not the person level.§§

The findings in this report are subject to at least six limitations. First, vaccination data for persons who lived in Los Angeles County at the time of their laboratory-confirmed infection but who were vaccinated outside of California were unavailable, leading to misclassification of their vaccination status; if vaccinated persons without accessible records were considered to be unvaccinated, the incidence in unvaccinated persons could be underestimated. Second, case ascertainment is based on passive surveillance, with known underreporting that might differ by vaccination status. Similarly, screening and testing behaviors might differ among groups. Third, COVID-19–associated hospitalizations were determined based on hospital admission and SARS-CoV-2 test dates alone, leading to the inclusion of incidental hospitalizations that were not associated with COVID-19. Fourth, COVID-19–associated deaths included deaths occurring ≤60 days after a first SARS-CoV-2 positive test date; therefore, some COVID-19–associated deaths might have been from other causes (excluding trauma). In addition, certain COVID-19–associated deaths might have been a result of long-term sequelae after 60 days and were not included. Fifth, lineage and Ct values were available only for a convenience sample of SARS-CoV-2 cases. Finally, all the assays used to generate Ct values for comparison were qualitative, and none is approved for use in quantitating the amount of viral nucleic acid present.

The findings in this report are similar to those from recent studies indicating that COVID-19 vaccination protects against severe COVID-19 in areas with increasing prevalence of the SARS-CoV-2 Delta variant (5,6). Efforts to increase COVID-19 vaccination coverage, in coordination with other prevention strategies, are critical to preventing COVID-19–related hospitalizations and deaths. Ongoing surveillance to characterize postvaccination infections, hospitalizations, and deaths will be important to monitor vaccine effectiveness, particularly as new variants emerge.

Acknowledgments

Kelsey Oyong; Heidi Sato; Rebecca Lee; Mireille Ibrahim; Kathleen Poortinga; Mirna Ponce-Jewell; Dulmini Wilson; Emmanuel Mendoza.

どうでも良いけど、Acknowledgmentsの中の佐藤平治さんだろうか？ それとも佐藤ハイジ（アーデルハイド）さんだろうか？