From Technion-Israel Institute of Technology, Haifa (Y.G.), the Hebrew University of Jerusalem (M.M.), and the Israeli Ministry of Health (O.B., E.J.H., S.A.-P., N.A.), Jerusalem, the Weizmann Institute of Science, Rehovot (Y.M.B.-O., R.M.), the Gertner Institute for Epidemiology and Health Policy Research, Sheba Medical Center Tel Hashomer, Ramat Gan (L.F., A.H.), Tel Aviv University, Tel Aviv (A.H.), and Ben Gurion University, Beersheva (E.J.H.) - all in Israel.
N Engl J Med. 2021 Dec 9;385(24):e85. doi: 10.1056/NEJMoa2114228. Epub 2021 Oct 27.
In December 2020, Israel began a mass vaccination campaign against coronavirus disease 2019 (Covid-19) by administering the BNT162b2 vaccine, which led to a sharp curtailing of the outbreak. After a period with almost no cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, a resurgent Covid-19 outbreak began in mid-June 2021. Possible reasons for the resurgence were reduced vaccine effectiveness against the delta (B.1.617.2) variant and waning immunity. The extent of waning immunity of the vaccine against the delta variant in Israel is unclear.
We used data on confirmed infection and severe disease collected from an Israeli national database for the period of July 11 to 31, 2021, for all Israeli residents who had been fully vaccinated before June 2021. We used a Poisson regression model to compare rates of confirmed SARS-CoV-2 infection and severe Covid-19 among persons vaccinated during different time periods, with stratification according to age group and with adjustment for possible confounding factors.
Among persons 60 years of age or older, the rate of infection in the July 11-31 period was higher among persons who became fully vaccinated in January 2021 (when they were first eligible) than among those fully vaccinated 2 months later, in March (rate ratio, 1.6; 95% confidence interval [CI], 1.3 to 2.0). Among persons 40 to 59 years of age, the rate ratio for infection among those fully vaccinated in February (when they were first eligible), as compared with 2 months later, in April, was 1.7 (95% CI, 1.4 to 2.1). Among persons 16 to 39 years of age, the rate ratio for infection among those fully vaccinated in March (when they were first eligible), as compared with 2 months later, in May, was 1.6 (95% CI, 1.3 to 2.0). The rate ratio for severe disease among persons fully vaccinated in the month when they were first eligible, as compared with those fully vaccinated in March, was 1.8 (95% CI, 1.1 to 2.9) among persons 60 years of age or older and 2.2 (95% CI, 0.6 to 7.7) among those 40 to 59 years of age; owing to small numbers, the rate ratio could not be calculated among persons 16 to 39 years of age.
These findings indicate that immunity against the delta variant of SARS-CoV-2 waned in all age groups a few months after receipt of the second dose of vaccine.
2020 年 12 月，以色列开始大规模接种 BNT162b2 疫苗，以对抗 2019 年冠状病毒病（COVID-19），这导致疫情迅速得到控制。在几乎没有严重急性呼吸综合征冠状病毒 2（SARS-CoV-2）感染病例的一段时间后，COVID-19 疫情于 2021 年 6 月中旬再次爆发。疫情复燃的可能原因是疫苗对 delta（B.1.617.2）变体的有效性降低和免疫力下降。以色列疫苗对 delta 变体的免疫力下降程度尚不清楚。
我们使用了 2021 年 7 月 11 日至 31 日期间从以色列国家数据库中收集的确诊感染和重症疾病数据，这些数据来自于所有在 2021 年 6 月之前完全接种疫苗的以色列居民。我们使用泊松回归模型比较了不同时间段接种疫苗的人群中 SARS-CoV-2 确诊感染和重症 COVID-19 的发生率，并按年龄组分层，同时考虑了可能的混杂因素。
在 60 岁及以上的人群中，2021 年 7 月 11 日至 31 日期间，在 1 月（首次有资格接种时）完全接种疫苗的人群中的感染率高于在 3 月（第二次接种疫苗时）完全接种疫苗的人群（比率为 1.6；95%置信区间[CI]为 1.3 至 2.0）。在 40 岁至 59 岁的人群中，在 2 月（首次有资格接种时）完全接种疫苗的人群的感染率比在 4 月（第二次接种疫苗时）高 1.7（95%CI 为 1.4 至 2.1）。在 16 岁至 39 岁的人群中，在 3 月（首次有资格接种时）完全接种疫苗的人群的感染率比在 5 月（第二次接种疫苗时）高 1.6（95%CI 为 1.3 至 2.0）。在首次有资格接种的当月完全接种疫苗的人群中，重症疾病的发病率与在 3 月（首次有资格接种时）完全接种疫苗的人群相比，60 岁及以上人群的发病率比为 1.8（95%CI 为 1.1 至 2.9），40 岁至 59 岁人群的发病率比为 2.2（95%CI 为 0.6 至 7.7）；由于人数较少，无法计算 16 岁至 39 岁人群的发病率比。
这些发现表明，所有年龄段人群在接受第二剂疫苗后几个月内，对 SARS-CoV-2 delta 变体的免疫力下降。
