Laboratory of Immunology, Biology Department, Faculty of Sciences, Universidad de Chile, Las Palmeras 3425, 7800003, Santiago, Chile.
Centro Ciencia & Vida, Av. Zañartu 1482, Santiago, Chile.
BMC Med. 2022 Jun 9;20(1):216. doi: 10.1186/s12916-022-02406-0.
Chile was severely affected by COVID19 outbreaks but was also one of the first countries to start a nationwide program to vaccinate against the disease. Furthermore, Chile became one of the fastest countries to inoculate a high percentage of the target population and implemented homologous and heterologous booster schemes in late 2021 to prevent potential immunological waning. The aim of this study is to compare the immunogenicity and time course of the humoral response elicited by the CoronaVac vaccine in combination with homologous versus heterologous boosters.
We compared the immunogenicity of two doses of CoronaVac and BNT162b2 vaccines and one homologous or heterologous booster through an ELISA assay directed against the ancestral spike protein of SARS-CoV-2. Sera were collected from individuals during the vaccination schedule and throughout the implementation of homologous and heterologous booster programs in Chile.
Our findings demonstrate that a two-dose vaccination scheme with CoronaVac induces lower levels of anti-SARS-CoV-2 spike antibodies than BNT162b2 in a broad age range (median age 42 years; interquartile range (IQR) 27-61). Furthermore, antibody production declines with time in individuals vaccinated with CoronaVac and less noticeably, with BNT162b2. Analysis of booster schemes revealed that individuals vaccinated with two doses of CoronaVac generate immunological memory against the SARS-CoV-2 ancestral strain, which can be re-activated with homologous or heterologous (BNT162b2 and ChAdOx1) boosters. Nevertheless, the magnitude of the antibody response with the heterologous booster regime was considerably higher (induction fold BNT162b2: 11.2x; ChAdoX1; 12.4x; CoronaVac: 6.0x) than the responses induced by the homologous scheme. Both homologous and heterologous boosters induced persistent humoral responses (median 122 days, IQR (108-133)), although heterologous boosters remained superior in activating a humoral response after 100 days.
Two doses of CoronaVac induces antibody titers against the SARS-CoV-2 ancestral strain which are lower in magnitude than those induced by the BNT162b2 vaccine. However, the response induced by CoronaVac can be greatly potentiated with a heterologous booster scheme with BNT162b2 or ChAdOx1 vaccines. Furthermore, the heterologous and homologous booster regimes induce a durable antibody response which does not show signs of decay 3 months after the booster dose.
智利曾受到 COVID19 爆发的严重影响，但也是最早开始全国范围内接种该疾病疫苗的国家之一。此外，智利成为最快为高比例目标人群接种疫苗的国家之一，并于 2021 年底实施同源和异源加强针计划，以防止潜在的免疫减弱。本研究旨在比较 CoronaVac 疫苗与同源或异源加强针联合使用后产生的体液免疫应答的免疫原性和时间过程。
我们通过 ELISA 检测针对 SARS-CoV-2 原始刺突蛋白的方法，比较了两剂 CoronaVac 和 BNT162b2 疫苗以及一种同源或异源加强针的免疫原性。在智利实施疫苗接种计划和同源及异源加强针计划期间，从个体中采集血清样本。
我们的研究结果表明，在广泛的年龄范围内（中位年龄 42 岁；四分位距（IQR）27-61），两剂 CoronaVac 疫苗接种方案诱导的针对 SARS-CoV-2 刺突蛋白的抗体水平低于 BNT162b2。此外，接种 CoronaVac 的个体的抗体产生随时间下降，而 BNT162b2 则下降不明显。加强针方案分析表明，接种两剂 CoronaVac 的个体对 SARS-CoV-2 原始株产生免疫记忆，可用同源或异源（BNT162b2 和 ChAdOx1）加强针重新激活。然而，异源加强针方案引起的抗体反应幅度明显更高（诱导倍数 BNT162b2：11.2x；ChAdoX1；12.4x；CoronaVac：6.0x）比同源方案引起的反应。同源和异源加强针均诱导持久的体液反应（中位时间 122 天，IQR（108-133）），尽管异源加强针在 100 天后仍能更好地激活体液反应。
两剂 CoronaVac 诱导针对 SARS-CoV-2 原始株的抗体滴度低于 BNT162b2 疫苗诱导的抗体滴度。然而，CoronaVac 诱导的反应可以通过 BNT162b2 或 ChAdOx1 疫苗的异源加强针方案大大增强。此外，同源和异源加强针方案诱导持久的抗体反应，在加强针接种后 3 个月内没有出现衰减迹象。
