COVAR study

COVID-19 VAccine Research: A community-based longitudinal observational cohort study on the immunogenicity and duration of vaccine-induced immune responses to different COVID-19 vaccines

Study Introduction

This is a large-scale community-based research study on COVID-19 vaccine effectiveness in Hong Kong organized by the School of Public Health, the University of Hong Kong. We will track individuals who have received any COVID-19 vaccine for a period of 3 years (2021 – 2024), to comprehensively monitor the immediate reactions, immune protection, respiratory virus infections and other health conditions after COVID-19 vaccination.





這是一項在香港本地進行的有關2019冠狀病毒病(COVID-19)疫苗效用的大型社區研究計劃,由香港大學公共衞生學院主辦,追踪COVID-19疫苗接種者為期3年 (2021 – 2024年),以全面監測接種COVID-19疫苗後的短期反應、免疫保護、呼吸道病毒感染及其他健康狀況。

Enrolment Eligibility

You are eligible to join the study if you meet the following requirements:

  • Individual aged 18 years old or above;
  • Are eligible to receive/ planned to receive any COVID-19 vaccine under the Hong Kong government’s COVID-19 Vaccination Program;
  • Willing to provide blood samples (if applicable) before receiving each dose of vaccination, as well as at least one month and one year afterwards; and
  • Willing to provide your phone number for communication purpose.
For those who have already received their third dose of vaccination are not eligible to join the study.


  • 18歲或以上人士;
  • 合資格及有意接種由香港政府2019冠狀病毒病疫苗接種計劃所提供的任何COVID-19疫苗;
  • 願意在(如適用)接種每劑COVID-19疫苗前、和至少在其一個月及一年後提供血液樣本;及
  • 願意提供電話號碼作聯繫用途。

COVID-19 is caused by the infection of the SARS-CoV-2 coronavirus, which has caused millions of deaths and major economic impacts worldwide since the beginning of 2020. Since 2021, different countries or regions around the world including Hong Kong has been offering free COVID-19 vaccination to the public with different types of COVID-19 vaccines. Due to differences in vaccine design and composition, these different COVID-19 vaccines could be different in terms of the ability to stimulate different branches of immune responses, to reduce disease severity or contagiousness after infection, the duration of immune protection and the protection against mutated strains. Therefore, there is an urgent need to conduct this research to help scientists develop better COVID-19 vaccines, to determine the level of community vaccination coverage needed and the need of repeated vaccination.

This study is financially supported by the Food and Health Bureau of Hong Kong and has been approved by the Institutional Review Board of the University of Hong Kong/ Hospital Authority Hong Kong West Cluster (UW21-336).





Complete a simple online registration form (Click “Join Now” )

Research personnel conduct initial screening on enrolment eligibility

Research personnel arrange a face-to-face interview with you for further assessment





During the interview, research personnel explain the details of the study to you and confirm your participation

During the study period, regular follow-up activities include questionnaires, blood collection and (if applicable) respiratory sample collection

For details, please refer to the Participant Information Sheet of this study.




No cost will be incurred for joining this study. To appreciate your support for our study, you will receive supermarket coupon during each regular follow-up for sample collection. In addition throughout the study, we may occasionally send you the results of your laboratory testing or the study findings of the cohort as a whole.


How to Join?
  • Click “Join Now” to complete a simple registration form online
    • (Due to popular demand, we aim to complete initial screening on enrolment eligibility and get back to you within two weeks after registration)
  • Site for research study:
    • Epi Research Site, School of Public Health, The University of Hong Kong (Map)
      • Address: Room 807, Hong Kong Plaza, 188 Connaught Road West, Sai Wan (MTR HKU Station, Exit B2)
      • Vaccine provided: - (For research activities only)
    • Sun Yat Sen Memorial Park Sports Centre (Map)
      • Address: G/F, 18 Eastern Street North, Sai Ying Pun (Exit A2 MTR Sai Ying Pun Station)
      • Vaccine provided: BioNTech
  • 按此「立即參加」進行簡單網上登記(報名反應熱烈,我們目標兩星期內回覆參於資格初步篩選結果)
  • 進行研究地點:
    • 香港大學公共衞生學院流行病學研究辦事處(地圖
      • 地址:西環干諾道西188號香港商業中心807室 (港鐵香港大學站B2出口)
      • 提供疫苗:-(只進行研究活動)
    • 中山紀念公園體育館(地圖
      • 地址:西營盤東邊街北18號地下(港鐵西營盤站A2出口)
      • 提供疫苗:復必泰
Contact the research team!
+852 9848 3299 or +852 9130 4428
    Office hours: Monday to Friday, 10am to 5pm (except public holidays)
+852 9848 3299 或 +852 9130 4428
The Science

About Coronavirus Disease 2019 (COVID-19)

The recent emergence of the new coronavirus disease 2019 (COVID-19) in late 2019 and the subsequent global pandemic has since caused millions of deaths and significant economic impacts globally. COVID-19 is caused by the infection of  SARS-CoV-2 coronavirus where disease severity varies widely, from asymptomatic infection, mild self-limiting disease with common respiratory symptoms, to severe disease requiring hospitalization that may lead to long-term symptoms or death.

About COVID-19 Vaccine

COVID-19 vaccination could provide protection against SARS-CoV-2 infection or severe disease after infection, and would also help to reduce community transmission by the accrual of population immunity. Due to different vaccine formulations, different COVID-19 vaccines such as inactivated virus vaccines (e.g. Sinovac, Sinopharm), mRNA vaccines (e.g. BioNTech, Moderna) and non-replicating adenovirus-vector-based vaccines (e.g. Oxford–AstraZeneca, Johnson & Johnson, Sputnik V) may have different capacities to stimulate different branches of immune responses (e.g.  humoral, cell-mediated and innate immunity) and require different vaccination frequencies. Like other vaccines, mild allergic reactions (side effects) such as mild fever, swelling or pain at injection site, or, in rare cases severe allergic reactions, may occur after COVID-19 vaccination.

For more information about COVID-19 vaccines, please visit the official website of the Hong Kong government’s COVID-19 Vaccination Programme.

About Us

Our team at the School of Public Health, the University of Hong Kong are experts in infectious disease epidemiology. This study is led by Dr. Nancy Leung and Prof. Benjamin Cowling.

The School of Public Health, LKS Faculty of Medicine of The University of Hong Kong (HKUSPH) has a long and distinguished history in public health education and high impact research. With world leading research in infectious diseases as well as on non-communicable diseases of both local and global importance, we have made significant contributions through its research and advocacy to improve the health of populations and individuals, both locally and globally. The School is a leading research and teaching hub in public health on influenza and other emerging viruses, control of non-communicable and infectious diseases, tobacco control, air pollution, psycho-oncology, behavioural sciences, exercise science, life-course epidemiology, and health economics, health services planning and management. Work done by us has informed international (e.g. the World Health Organization and the Food and Agriculture Organization), national and local public health policies.

The School of Public Health hosts the WHO Collaborating Centre (WHO CC) for Infectious Disease Epidemiology and Control. With a view to protecting the public's health in Hong Kong and across the region, the WHO CC aims to coordinating research on the control and prevention of infectious diseases and providing local and regional education and training in infectious disease epidemiology and control. Members of the WHO CC are involved in the response to COVID-19 and conducted a range of scientific research projects. The team has created a website (click here to visit) to share the latest scientific findings and the implications for evidence-based public health policies on the ongoing COVID-19 pandemic.











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