Is Karachi Knocking at Herd Immunity? A Possible Reason for Decline in SARS-CoV-2 Infections

Autor: Arshi Naz, Munira Borhany, Shabnum Khawaja, Shakir Ahmed, Samreen Kulsoom Zaidi, Jawwad Hassan, Tahir Shamsi, Faiza Rezwan, Asma Danish, Samra Waheed, Mehjabeen Imam
Rok vydání: 2020
Předmět:
Zdroj: SSRN Electronic Journal.
ISSN: 1556-5068
Popis: Background: There is a sharp decline in newSARS-CoV-2 cases in Karachi from July onwards; most of them were asymptomatic. Seroconversion rates vary markedly in different countries. Herd immunity for this virus is considered to be at 60-70%. Previously, 36% of seropositivity was reported in the adult population of Karachi in July this year. The current study was conducted to report if seroprevalence has reached the threshold of herd immunity. Methods: This was a prospective cross-sectional study conducted in the first and second weeks of September 2020 at the National Institute of Blood disease and Bone Marrow Transplantation Hospital (NIBD), Karachi, Pakistan. Blood samples were collected from different segments of the population of Karachi workforce/community. An anti-SARS-CoV-2 test was performed using ECLIA from Roche Diagnostics International. Results: A total of 2404 subjects’ blood samples were received from healthcare workers, the industrial workforce, and healthy blood donors. Seroprevalence in industrial workers was highest (70%) as compared to healthcare workers (40%). Overall seropositivity in males (39%) was higher than females (16%). Blood donors (all males) showed a seropositivity of 37.8%. The co-morbid state was not significantly associated with seropositivity (p-value >0.05). Total cases of antibody-positive were 1322 of 2100 (55 %). Conclusion: Our results confirmed the current seroprevalence of 55% in the adult population in Karachi. There was a sharp rise from 36% reported previously in July. This rise coincided with a sharp decline in new reported COVID cases. We can conclude that we are approaching the target of herd immunity in Karachi.
Databáze: OpenAIRE