ABSTRACT
Long-term solutions against SARS-CoV-2 infections require understanding of immune protection induced by different vaccine COVID-19 formulations. We investigated humoral and cellular immunity induced by Sinopharm (BBIBP-CorV) in a region of high SARS-CoV-2 seroprevalence. Levels of IgG antibodies to SARS-CoV-2 spike protein and its receptor-binding domain (RBD) were determined 24-weeks. Cellular immunity was investigated using a commercially available IFN-{gamma} release assay to SARS-CoV-2 spike (Ag1 and 2) and extended genome antigens (Ag3). Increasing IgG seropositivity to Spike protein and RBD was observed post-vaccination. Seropositivity was reduced in those over 50 years and raised in females and those with prior COVID-19. After 20 weeks post-vaccination, only one third of participants had positive T cell responses to SARS-CoV-2 antigens. Prior COVID-19 impacted IFN{gamma} responses, with reactivity enhanced in those infected earlier. The frequency of IFN{gamma} responses was highest to extended genome antigen set. Overall, BBIBP-CorV- induced antibody responses were impacted by age, gender and prior COVID-19. Cellular immunity was present in a limited number of individuals after 20 weeks but was enhanced by prior infection. This suggests the need for booster vaccinations in older individuals. BBIBP-CorV-induced cellular activation is broader than to spike, requiring further study to understand how to monitor vaccine effectiveness.
ABSTRACT
Serial household antibody sero-surveys informs the pandemic where testing is non-uniform. Young populations with intergenerational co-residence may have different transmission dynamics. We conducted two serial cross-sectional surveys in April and June 2020 in low- and high-transmission neighborhoods of Karachi, Pakistan, using random sampling. Symptoms were assessed and blood tested for antibody using chemiluminescence. Seroprevalence was adjusted using Bayesian regression and post stratification. CRI with 95% confidence intervals was obtained. We enrolled 2004 participants from 406 households. In June 8.7% (95% CI 5.1-13.1) and 15.1% (95% CI 9.4-21.7) were infected in low- and high-transmission-areas respectively compared with 0.2% (95% CI 0-0.7) and 0.4% (95% CI 0-1.3) in April. Conditional risk of infection was 0.31 (95% CI 0.16-0.47) and 0.41(95% CI 0.28-0.52) respectively with only 5.4% symptomatic. Rapid increase in seroprevalence from baseline is seen in Karachi, with a high probability of infection within household. Article Summary LineRapid increase in seroprevalence of antibodies against SARS-CoV-2 was seen in Karachi, Pakistan from April to June 2020 with a high conditional risk of infection within the household
