Aijaz Javeria, Hussain Shakir, Naseer Fouzia, Kanani Fatima, Anis Sabiha, Sarfaraz Samreen, Saeed Saima, Farooq Hina, Jamal Saba
Molecular Biology Section, Pathology Department, Indus Hospital & Health Network, Karachi 75190, Pakistan.
Chemical Pathology Section, Pathology Department, Indus Hospital & Health Network, Karachi 75190, Pakistan.
Vaccines (Basel). 2022 Apr 28;10(5):692. doi: 10.3390/vaccines10050692.
Fifty five percent of the Pakistani population is still unvaccinated with the two-dose protocol of COVID-19 vaccines. This study was undertaken to determine the seroconversion rate and antibody titers following the two-dose BBIBP-CorV protocol, and to compare these variables in unvaccinated, COVID-19 recovered individuals (total = 180) at Indus Hospital and Health Network, Karachi. Pseudotyped lentivirus antibody neutralization assays and SARS-CoV-2 IgG Quant II (Abbott) immunoassays were performed 4-8 weeks following the second dose of the BBIBP-CorV or PCR positivity/onset of symptoms of COVID-19. Seroconversion rate, using neutralization assays, in vaccinated individuals was lower (78%) than that in unvaccinated, COVID-19-recovered individuals with moderate to severe infection (97%). Prior PCR positivity increased serocoversion rate to 98% in vaccinated individuals. Immunoassays did not, however, reveal significant inter-group differences in seroconversion rates (≥95% in all groups). Log10 mean antibody neutralizing titers following the two-dose BBIBP-CorV protocol (IC50 = 2.21) were found to be significantly less than those succeeding moderate to severe COVID-19 (IC50 = 2.94). Prior SARS-CoV-2 positivity significantly increased post-vaccination antibody titers (IC50 = 2.82). Similar inter-group titer differences were obtained using the immunoassay. BBIBP-CorV post-vaccination titers may, thus, be lower than those following natural, moderate to severe infection, while prior SARS-CoV-2 exposure increases these titers to more closely approximate the latter.
55%的巴基斯坦人口仍未按照两剂次新冠疫苗接种方案接种新冠疫苗。本研究旨在确定两剂次BBIBP-CorV接种方案后的血清转化率和抗体滴度，并比较卡拉奇印度河医院和健康网络中未接种疫苗、感染新冠病毒后康复的个体（共180人）的这些变量。在第二剂BBIBP-CorV接种后4至8周，或新冠病毒PCR检测呈阳性/出现症状后，进行假型慢病毒抗体中和试验和SARS-CoV-2 IgG Quant II（雅培）免疫测定。使用中和试验，接种疫苗个体的血清转化率（78%）低于未接种疫苗、感染新冠病毒后康复且感染程度为中度至重度的个体（97%）。既往PCR检测呈阳性使接种疫苗个体的血清转化率提高到98%。然而，免疫测定未显示各群体之间血清转化率存在显著差异（所有群体均≥95%）。发现两剂次BBIBP-CorV接种方案后的Log10平均抗体中和滴度（IC50 = 2.21）显著低于中度至重度新冠病毒感染后的滴度（IC50 = 2.94）。既往SARS-CoV-2检测呈阳性显著提高了接种疫苗后的抗体滴度（IC50 = 2.82）。使用免疫测定也获得了类似的群体间滴度差异。因此，接种BBIBP-CorV后的滴度可能低于自然发生的中度至重度感染后的滴度，而既往SARS-CoV-2暴露会使这些滴度升高，更接近后者。
