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COVID-19 vaccines Adverse events Response and Evaluation (CARE) Programme

Science Lab

COVID-19 is a global pandemic that is currently the highest public health priority worldwide. The COVID-19 vaccine is expected to play an important role in the control of the global pandemic. On 23 December 2020, the Chief Executive announced that 22.5 million shots of COVID-19 vaccines have been secured for Hong Kong citizens. The Government-led COVID-19 vaccine campaign has been launched since February 2021. Similar to the development of all novel medicines, COVID-19 vaccines were developed and trialled in initially small groups of specific and selected participants, followed by larger trial numbers. In the case of COVID vaccines, vaccine development/manufacturing was carried out in parallel with clinical trials to facilitate more efficient approval processes. Like other new drugs and vaccines, indeed, it is possible that some rare adverse events may only become apparent following real-world usage and adverse reaction profiles may differ in different age groups and among people with different characteristics. Hence, it is immensely important to closely monitor the safety of the vaccines as they begin to be taken up by the citizens of Hong Kong. It is important to develop a comprehensive surveillance to monitor potential adverse events of COVID-19 vaccines while in widespread clinical use.

Currently, two types of vaccines are available for the mass vaccination programme in Hong Kong (subject to the approval of the Hong Kong Government and availability from the manufacturers): (1) COVID-19 mRNA Vaccine BNT162b2 (Pfizer/BioNTech); and (2) CoronaVac (Sinovac Life Sciences, Beijing, China). The vaccines were purchased by the Hong Kong Government and the manufacturers are not involved in this proposed study.

At the time of the CARE Programme, only scant reports of possible rare adverse events were reported with no further information about medium and long-term outcomes on any of the COVID-19 vaccines. In this programme, we actively collect data on potential adverse outcomes by conducting real-time surveillance on the general population, including vulnerable groups; provide a framework to rapidly detect, prioritise and evaluate emerging safety information derived from an intensive monitoring programme from sources including adverse drug reporting system from the Department of Health (DH) Drug Office, electronic health records of Hospital Authority (HA), observational studies and other data sources; for prompt evaluation of detected safety issues to determine the risk-benefit profile of the vaccines. We will also continuously screen for risks from the global literature to monitor potential risks that may arise in Hong Kong.





Study Backgroud





Petri Dish


Background incidence of  AESI 

To provide background incidence of adverse events of special interest (AESI) including but not limited to rare or serious adverse events. A list of AESI has been endorsed by the World Health Organisation (WHO) and used by EMA-funded ACCESS (vACCine covid-19 monitoring readinESS) project. We estimate the age and sex specific incidences of these AESI before the commencement of the vaccination programme and report the likely frequency of putative adverse events expected from the background incidence.

Active surveillance

To conduct weekly surveillance to identify selected AESI and conduct causality assessment as an early warning system using electronic health record from HA data (public sector). 


Record-linkage study

To conduct a record-linkage study to link the DH data on vaccination records and the HA records (outcomes that require hospitalisation) to conduct cohort studies to evaluate the relative risk. With the AESI cases obtained from HA, we also conduct case-control and self-controlled studies to evaluate the association.  


Intensive monitoring

To conduct intensive monitoring of approximately more than 4000 vaccine recipients to allow us to ascertain details of ALL adverse events inclusive of common adverse events including injection site inflammation, headache and others. 

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