Effectiveness of Covid-19 Vaccination in Eswatini Against SARS-CoV-2 Associated Hospitalization and Death

Overview

Since late December 2019, the novel human coronavirus (SARS-CoV-2) first reported in China, has spread worldwide. Vaccines to prevent SARS-CoV-2 infections have been developed in record time and several candidate vaccines have completed Phase 2a/b and Phase 3 clinical trials. Coronaviruses (CoVs) are spherical, enveloped viruses with positive-sense single-stranded RNA genomes. One fourth of their genome is responsible for coding structural proteins, such as the Spike (S) glycoprotein, envelope, membrane, and nucleocapsid proteins. Envelope, membrane, and nucleocapsid proteins are mainly responsible for virion assembly whilst the S protein is involved in receptor binding, mediating virus entry into host cells during CoVs infection via different receptors. SARS-CoV-2 belongs to the phylogenetic lineage B of the genus Betacoronavirus and it recognizes the ACE2 as the entry receptor. It is the seventh CoV known to cause human infections and the third known to cause severe disease after SARS-CoV and MERS-CoV. AZD1222 is a recombinant replication-defective chimpanzee adenovirus vaccine expressing the SARS-CoV-2 S surface glycoprotein. Development of AZD1222, previously referred to as ChAdOx1 nCoV-19, was initiated by the University of Oxford, UK, with subsequent transfer of development activities to AstraZeneca. The ChAdOx1 platform has been used in 14 clinical studies sponsored by the University of Oxford with immunogens from multiple pathogens such as influenza, tuberculosis, malaria, chikungunya, Zika, MERS-CoV, and Meningitis B. Over 360 healthy adult participants have received ChAdOx1-vectored vaccines in these studies. These vaccines demonstrated robust immunogenicity after a single dose and favourable safety profiles, with no vaccine-related serious adverse events (SAEs).

This will be open-label, single-arm implementation study in Eswatini. All individuals who register on the National Vaccination Registry will be eligible for enrolment. Participants will receive appointments for vaccination using the registry. Vaccination will be overseen by trained personnel. At enrolment participants will receive an intramuscular injection of AZ1222, a second dose will be given 10 weeks after the first injection. Surveillance for vaccine effectiveness will be performed at designated hospitals. A prospective hospital-based, case-control study with test-negative controls (test-negative case-control design) and optionally other hospital controls (standard case-control design) will be conducted in parallel with the implementation study. Data will be collected through a network of hospitals located in Eswatini. A hospital-based case control study is an efficient design well suited to study for effectiveness against severe disease, and potentially allows for detailed medical information and additional data collection directly from the patient or healthcare provider. In addition, the study aims to determine the vaccine effectiveness (VE) of AZ1222 against severe disease due to the B.1.351 variant circulating in Southern Africa and other new variants that might evolve.