From the Faculty of Industrial Engineering and Management, Technion-Israel Institute of Technology, Haifa (Y.G.), the Department of Statistics and Data Science, Hebrew University of Jerusalem (M.M.), and the Israeli Ministry of Health (O.B., N.A., S.A.-P.), Jerusalem, the Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot (Y.M.B.-O., R.M.), the Biostatistics and Biomathematics Unit, Gertner Institute for Epidemiology and Health Policy Research, Sheba Medical Center, Ramat Gan (L.S.F., A.H.), and the Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv (A.H.) - all in Israel.
N Engl J Med. 2022 Jun 9;386(23):2201-2212. doi: 10.1056/NEJMoa2118946. Epub 2022 May 25.
Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) provides natural immunity against reinfection. Recent studies have shown waning of the immunity provided by the BNT162b2 vaccine. The time course of natural and hybrid immunity is unknown.
Using the Israeli Ministry of Health database, we extracted data for August and September 2021, when the B.1.617.2 (delta) variant was predominant, on all persons who had been previously infected with SARS-CoV-2 or who had received coronavirus 2019 vaccine. We used Poisson regression with adjustment for confounding factors to compare the rates of infection as a function of time since the last immunity-conferring event.
The number of cases of SARS-CoV-2 infection per 100,000 person-days at risk (adjusted rate) increased with the time that had elapsed since vaccination with BNT162b2 or since previous infection. Among unvaccinated persons who had recovered from infection, this rate increased from 10.5 among those who had been infected 4 to less than 6 months previously to 30.2 among those who had been infected 1 year or more previously. Among persons who had received a single dose of vaccine after previous infection, the adjusted rate was low (3.7) among those who had been vaccinated less than 2 months previously but increased to 11.6 among those who had been vaccinated at least 6 months previously. Among previously uninfected persons who had received two doses of vaccine, the adjusted rate increased from 21.1 among those who had been vaccinated less than 2 months previously to 88.9 among those who had been vaccinated at least 6 months previously.
Among persons who had been previously infected with SARS-CoV-2 (regardless of whether they had received any dose of vaccine or whether they had received one dose before or after infection), protection against reinfection decreased as the time increased since the last immunity-conferring event; however, this protection was higher than that conferred after the same time had elapsed since receipt of a second dose of vaccine among previously uninfected persons. A single dose of vaccine after infection reinforced protection against reinfection.
感染严重急性呼吸综合征冠状病毒 2（SARS-CoV-2）可提供针对再次感染的自然免疫力。最近的研究表明，BNT162b2 疫苗提供的免疫力正在减弱。自然和混合免疫的时间过程尚不清楚。
利用以色列卫生部数据库，我们提取了 2021 年 8 月和 9 月的数据，当时 B.1.617.2（德尔塔）变体占主导地位，研究对象包括以前感染过 SARS-CoV-2 或接种过 2019 年冠状病毒疫苗的所有人。我们使用泊松回归模型，调整混杂因素，比较了末次免疫事件后时间与感染率的关系。
每 100000 人日的 SARS-CoV-2 感染病例数（调整后的发病率）随 BNT162b2 接种或既往感染后时间的延长而增加。在未接种疫苗且已从感染中康复的人群中，这一发病率从 4-6 个月前感染的人群中的 10.5 例增加到 1 年或以上前感染的人群中的 30.2 例。在既往感染后接种过一剂疫苗的人群中，既往接种不到 2 个月的人群调整后发病率较低（3.7），但至少接种 6 个月前接种的人群发病率增加至 11.6。在既往未感染且接种了两剂疫苗的人群中，调整后发病率从接种不到 2 个月的人群中的 21.1 例增加到至少接种 6 个月的人群中的 88.9 例。
在既往感染过 SARS-CoV-2 的人群中（无论其是否接种过任何剂量的疫苗，或是否在感染前或感染后接种过疫苗），末次免疫事件后时间的延长会降低再次感染的保护作用；然而，与既往未感染者接种第二剂疫苗后相同时间相比，这种保护作用更高。感染后接种一剂疫苗可增强对再次感染的保护作用。
