Neutralizing Antibody Response to BBIBP-CorV in Comparison with COVID-19 Recovered, Unvaccinated Individuals in a Sample of the Pakistani Population

Abstract

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 n = 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.

Effect of age and prior COVID-19 on BBIBP-CorV (Sinopharm) vaccination- induced antibody responses in a region with high seroprevalence

“…Those with a history of COVID-19 displayed signi cantly greater higher antibody seropositivity than those who did not for up to 16 weeks after vaccination. This correlates with reports by Aijaz et al who observed that seropostivity rates from natural infection were greater than those induced by Sinopharm vaccination [19]. Antibody positivity protects against SARS-CoV-2 reinfection for at least 7 months [39].…”

“…However, it correlates with the lower [29] antibody responses to BBIBP-CorV measured (50%) in dialysis patients in the UAE measured at 6 weeks of vaccination [18]. It also correlates with data from Pakistan that showed 78% of antibody responses to RBD in individuals vaccinated with BBIBP-CorV [19].…”

“…In Sri Lanka, more than 90% seropositivity was observed was seen that 6 weeks post-vaccination [15,17]. A study from the United Arab Emirates showed seropositivity of 78% in the general population after full vaccination [18], with a similar result shown in a report from Pakistan [19].…”

“…A study from Karachi showed average seropositivity of 36% between April and July 2020, varying between industrial employees (50%), community (34%), and healthcare workers (13%) [18]. General population based serial serosurveys for COVID-19 in Karachi showed a rise in prevalence rates to 22% by August 2020 [19].…”

A Comprehensive Review on the Current Vaccines and Their Efficacies to Combat SARS-CoV-2 Variants

“…In a recent cohort-based study conducted in Pakistan, the titers of neutralizing antibodies after two doses of the BBIBP vaccine were lower than those induced by the natural SARS-CoV-2 infection. However, vaccine administration in people with prior exposure to SARS-CoV-2 significantly increases the neutralizing antibody titers [ 93 ]. In another study conducted in Thailand, the efficacy of heterologous booster doses of mRNA (BNT162b2 or mRNA-1273) or recombinant adenovirus-based vaccine (AZD122) on BBIBP-CorV-primed people was assessed.…”