Study title: Evaluation of Vaccine Effectiveness Amongst Adults Living with Co-morbidities following Routine Introduction of COVID-19 Vaccine in Harare, Zimbabwe: A Prospective Cohort Study

Lead Researcher(s): Katharina Kranzer, Leolin Katsidzira

Funder(s): Bill and Melinda Gates Foundation, China Centre of Disease Control

Partner(s): Ministry of Health and Child Care, Harare City Health, Sally Mugabe Central Hospital, Parirenyatwa Group of Hospitals, Chitungwiza Hospital, University of Sheffield, Zvitambo Institute for Maternal and Child Health Research, London School of Hygiene and Tropical Medicine, University College London, University of Sheffield

Background

Coronavirus disease 2019 (COVID-19) vaccines have been a key pillar of the pandemic response at global, national, and local levels. Their roll-out has reduced morbidity, severity and deaths. Zimbabwe started its vaccination campaign in February 2021 predominantly using Sinopharm and Sinovac with >13 million vaccine doses administered in October 2023. Vaccine effectiveness of Sinopharm and Sinovac among people who are most at risk for severe COVID-19 disease i.e. those with co-morbidities such as HIV, hypertension and diabetes has never been assessed in sub-Saharan Africa.

Study aim(s)

To assess the effectiveness of COVID-19 vaccination amongst adults living with chronic diseases (diabetes, hypertension, and HIV) following routine introduction in Zimbabwe.

To characterize T-cell immunity generated by infection and inactivated vaccines in adults with chronic conditions.

To characterize functional SARS-CoV-2 antibody responses in serum and the mucosal compartment generated by infection and inactivated vaccines in adults with chronic conditions.

Study design

A total of 4017 adults were enrolled from HIV clinics and chronic disease clinics across three hospitals and three polyclinics in Harare and Chitungwiza and followed for a medium of 12 months. At baseline socio-demographics, past medical history and vaccination status was determined. Participants were followed by phone fortnightly to determine incidence of symptomatic SARS-CoV-2 infections, hospitalizations and mortality. A cross-sectional detailed immunogenicity sub-study exploring blood and mucosal immunity to infection and SARS-CoV-2 vaccines was embedded within the cohort.

Duration

May 2022 - December 2025