ABSTRACT
BACKGROUND: From May to December 2021, Bangladesh experienced a major surge in the Delta variant of SARS-CoV-2. The earlier rollout of several vaccines offered the opportunity to evaluate vaccine effectiveness against this variant. METHODS: A prospective, test-negative case-control study was conducted in five large hospitals in Dhaka between September and December 2021. The subjects were patients of at least 18 years of age who presented themselves for care, suffering COVID-like symptoms of less than 10 days' duration. The cases had PCR-confirmed infections with SARS-CoV-2, and up to 4 PCR test-negative controls were matched to each case, according to hospital, date of presentation, and age. Vaccine protection was assessed as being the association between the receipt of a complete course of vaccine and the occurrence of SARS-CoV-2 disease, with symptoms beginning at least 14 days after the final vaccine dose. RESULTS: In total, 313 cases were matched to 1196 controls. The genotyping of case isolates revealed 99.6% to be the Delta variant. Receipt of any vaccine was associated with 12% (95% CI: -21 to 37, p = 0.423) protection against all episodes of SARS-CoV-2. Among the three vaccines for which protection was evaluable (Moderna (mRNA-1273); Sinopharm (Vero Cell-Inactivated); Serum Institute of India (ChAdOx1 nCoV-19)), only the Moderna vaccine was associated with significant protection (64%; 95% CI: 10 to 86, p = 0.029). Protection by the receipt of any vaccine against severe disease was 85% (95% CI: 27 to 97, p = 0.019), with protection estimates of 75% to 100% for the three vaccines. CONCLUSIONS: Vaccine protection against COVID-19 disease of any severity caused by the Delta variant was modest in magnitude and significant for only one of the three evaluable vaccines. In contrast, protection against severe disease was high in magnitude and consistent for all three vaccines. Because our findings are not in complete accord with evaluations of the same vaccines in more affluent settings, our study underscores the need for country-level COVID-19 vaccine evaluations in developing countries.
ABSTRACT
Oxford AstraZeneca (Covishield) vaccine is the 1st vaccine administered in Bangladesh to prevent the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The antibody response after 1st and 2nd doses of this vaccine was assessed in health care workers of Dhaka Medical College Hospital, Bangladesh. Blood sample was collected from healthcare workers (teachers, clinicians and medical staff) after 28 days of 1st vaccination and 14 days after 2nd vaccination. Quantitative post-vaccination antibody responses were measured using the chemiluminescent immunoassay, ADVIA Centaur (Siemens, Munich, Germany) SARS-CoV-2 IgG (COV2G) assay (output index was 1.00). Vaccine related antibody was found in 126 (41%) participants after 1st dose of AstraZeneca vaccine. After 2nd dose of vaccine, reactive level of antibody was found in 172 (93%) participants. Antibody responses were significantly higher in previously infected participants compared to participants who had no history of previous COVID-19 after 1st dose (51.92+or-50.85 vs 23.67+or-41.07, p=0.001) as well as 2nd dose of vaccine (64.12+or-97.76 vs 35.04+or-64.84, p=0.001). No difference in antibody response was observed among participants with or without comorbidities. Oxford AstraZeneca Covishield vaccine induces a strong immune response after two doses of vaccination.