Seroprevalence of immunoglobulin G antibodies against SARS-CoV-2 in Cyprus

Four vaccines that have been authorized in the European Union offer different levels of protection against SARS-CoV-2 by generating immune responses against the spike receptor-binding domain (RBD) of the virus. Monitoring the levels of IgG antibodies against the SARS-CoV-2 is important during the coronavirus disease 2019 (COVID-19) pandemic to plan an adequate and evidence-based public health response. We compared the levels of serum IgG antibodies against SARS-CoV-2 spike protein in three groups: i) individuals without evidence of prior infection with SARS-CoV-2 who received one or two doses of either an mRNA-based (Comirnaty BNT162b2/Pfizer-BioNTech or Spikevax mRNA-1273/Moderna) or an adenoviral-based vaccine (Vaxzervia ChAdOx1 nCoV-19 /Oxford-Astra Zeneca) (n=227), ii) unvaccinated individuals with evidence of prior infection with SARS-CoV-2 (n=109), and iii) individuals with evidence of prior infection with SARS-CoV-2 who received at least one dose of a vaccine (n=30). Unvaccinated individuals without evidence of prior infection with SARS-CoV-2 were used as a control group (n=211). Our results indicate that vaccine-induced responses lead to higher levels of IgG antibodies compared to those produced following infection with the virus. In agreement with previous studies, our results suggest that among individuals previously infected with SARS-CoV-2, even a single dose of a vaccine is adequate to elicit high levels of humoral immunity.

在欧盟获批的四款疫苗可通过针对严重急性呼吸综合征冠状病毒2型（SARS-CoV-2）的刺突受体结合域（spike receptor-binding domain，RBD）激发免疫应答，从而对该病毒提供不同水平的保护。在2019冠状病毒病（COVID-19）大流行期间，监测针对SARS-CoV-2的IgG抗体（Immunoglobulin G）水平，对于制定充分且基于证据的公共卫生应对方案具有重要意义。本研究对比了三类人群体内针对SARS-CoV-2刺突蛋白的血清IgG抗体水平：① 无既往SARS-CoV-2感染证据、接种1剂或2剂mRNA类疫苗（Comirnaty BNT162b2/辉瑞-生物泰克（Pfizer-BioNTech）或Spikevax mRNA-1273/莫德纳（Moderna））或腺病毒载体疫苗（Vaxzervia ChAdOx1 nCoV-19/牛津-阿斯利康（Oxford-Astra Zeneca））的个体，样本量n=227；② 未接种疫苗但存在既往SARS-CoV-2感染证据的个体，样本量n=109；③ 存在既往SARS-CoV-2感染证据且至少接种1剂疫苗的个体，样本量n=30。本研究将无既往SARS-CoV-2感染证据且未接种疫苗的个体设为对照组，样本量n=211。研究结果显示，疫苗诱导的免疫应答所产生的IgG抗体水平高于病毒自然感染后产生的抗体水平。与既往研究结果一致，本研究表明，在既往感染过SARS-CoV-2的人群中，仅接种1剂疫苗即可充分激发高水平的体液免疫（humoral immunity）。