Cohort Study to Measure COVID-19 Vaccine Effectiveness Among Health Workers in Azerbaijan

2. Background and study rationale In late 2019 a novel severe acute respiratory syndrome - coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), emerged. On January 30, 2020, WHO declared COVID-19 a public health emergency of international concern. On 11 March 2020, the World Health Organization declared COVID-19 a pandemic. The first case of COVID-19 was detected in Azerbaijan end of February, 2020, and since then 236,012 cases and 3,235 deaths has been reported in the country (data as of 8 March 2021).1

Effective and safe vaccines against COVID-19 are vital for controlling the pandemic. International collaborative efforts have accelerated the development of COVID-10 vaccines. As of 5 March 2021, there were 182 vaccines in pre-clinical development, and 79 vaccines in clinical development2. As of 18 February 2021, at least seven different vaccines across three platforms had been rolled out in countries, including the Coronac vaccine produced by Chinese company Sinopharm.

Evaluating the real-world COVID-19 vaccine performance is critical for understanding the risks and benefits of vaccination programs. Many factors impact real-world vaccine effectiveness (VE), including vaccine transportation and storage and how patients are vaccinated. In addition, the people who get the vaccine in clinical trials are often young and healthy, and therefore different from those who will receive vaccines in the real world. Post-licensing VE studies can also answer questions about effectiveness by age-group and underlying medical conditions, duration of vaccine protection, relative effectiveness of different vaccines, relative effectiveness of one dose vs. two doses, and effectiveness of the vaccine against new strains of SARS-CoV-2.

Health workers (HW) have been targeted for this study for a number of reasons. Azerbaijan has prioritized HWs for vaccination in line with the recommendations of the WHO SAGE and the European Technical Advisory Group on immunizations for use of COVID-19 vaccines when supply is limited. HWs provide a critical essential service in the COVID-19 pandemic response. HWs are at high risk of acquiring infection and associated morbidity and mortality, and also pose a risk of onward transmission to people who are also at high risk of serious COVID-19 outcomes. Ensuring that HWs receive an effective vaccine is also guided by the principle of reciprocity because HWs play critical roles in the COVID-19 response, working under intense and challenging conditions. Targeting HWs in this study offers an opportunity to determine the effectiveness of the vaccine in a population in which it is critical that an effective vaccine be deployed. While the HW population is not perfectly representative of the population of Azerbaijan, having an early understanding of the effectiveness of the vaccine in this population can inform decisions about vaccine use in the general population.

Immunization of HWs in Azerbaijan with Coronavac started in January 18, and the second dose has been administered to more than 60% of HWs by 15 March 2021. At the same time, it is estimated that 45-60% of health workers at the six target hospitals have received at least one dose and 60% of those have also received second dose of the vaccine.