Waning effectiveness against COVID-19-related hospitalization, severe complications, and mortality with two to three doses of CoronaVac and BNT162b2: a case–control study

ABSTRACT

Background: This study aims to evaluate waning effectiveness against severe and fatal COVID-19 with two to three doses of CoronaVac/BNT162b2, where data are limited. Methods: A case–control study included individuals aged ≥18 years, unvaccinated or received two to three doses of CoronaVac/BNT162b2, using electronic healthcare databases in Hong Kong. Those with first COVID-19-related hospitalization, severe complications, or mortality between 1 January and 15 August 2022 were defined as cases and matched with up-to-10 controls by age, sex, index date, and Charlson Comorbidity Index. Vaccine effectiveness (VE) against COVID-19-related outcomes was estimated at different time intervals from second and third-dose vaccination (0–13 up-to 210–240 days) using conditional logistic regression adjusted for comorbidities and medications. Results: By 211–240 days after second dose, VE against COVID-19-related hospitalization reduced to 46.6% (40.7–51.8%) for BNT162b2 and 36.2% (28.0–43.4%) for CoronaVac, and VE against COVID-19-related mortality were 73.8% (55.9–84.4%) and 76.6% (60.8–86.0%). After third dose, VE against COVID-19-related hospitalization decreased from 91.2% (89.5–92.6%) for BNT162b2 and 76.7% (73.7–79.4%) for CoronaVac at 0–13 days, to 67.1% (60.4–72.6%) and 51.3% (44.2–57.5%) at 91–120 days. VE against COVID-19-related mortality for BNT162b2 remained high from 0–13 days [98.2% (95.0–99.3%)] to 91–120 days [94.6% (77.7–98.7%)], and for CoronaVac reduced from 0–13 days [96.7% (93.2–98.4%)] to 91–120 days [86.4% (73.3–93.1%)]. Conclusions: Significant risk reduction against COVID-19-related hospitalization and mortality after CoronaVac or BNT162b2 vaccination was observed for >240 and >120 days after second and third doses compared to unvaccinated, despite significant waning over time. Timely administration of booster doses could provide higher levels of protection.

KEYWORDS:

• COVID-19
• waning vaccine effectiveness
• CoronaVac
• BNT162b2
• Omicron

Acknowledgements

We gratefully acknowledge the Centre for Health Protection, Department of Health and Hospital Authority for facilitating data access. ICKW is partially supported by the Laboratory of Data Discovery for Health (D24H) funded by AIR@InnoHK administered by the Innovation and Technology Commission. The corresponding authors had full access to all the data in the study and took final responsibility for the decision to submit for publication. Concept and design were prepared by VKCY, EYFW, ICKW, EWC. Acquisition, analysis, or interpretation of data was formulated by VKCY, EYFW, XY, FTTL, CSLC, XL, CKHW, PHL, TM, SQ, ICKW, EWC. Drafting of the manuscript was bone by VKCY, EYFW, AHYM. Critical revision of the manuscript for important intellectual content was done by all the authors. Statistical analysis: VKCY, EYFW, XY. Administrative, technical, or material support was given by ICKW, EWC. ICKW, EWC supervised the whole process.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data sharing

Data are not available as the data custodians (the Hospital Authority and the Department of Health of Hong Kong SAR) have not given permission for sharing due to patient confidentiality and privacy concerns. Local academic institutions, government departments, or non-governmental organizations may apply for the access to data through the Hospital Authority’s data sharing portal (https://www3.ha.org.hk/data).

Additional information

Funding

This work was funded by a research grant from the Food and Health Bureau of the Government of the Hong Kong Special Administrative Region (HMRF Commissioned Research on the Novel Coronavirus Disease; Principal Investigator (WP2): EWC; Ref: COVID1903011). EYFW has received research grants from the Food and Health Bureau of the Government of the Hong Kong Special Administrative Region, and the Hong Kong Research Grants Council, outside the submitted work. FTTL has been supported by the RGC Postdoctoral Fellowship under the Hong Kong Research Grants Council and has received research grants from the Food and Health Bureau of the Government of the Hong Kong Special Administrative Region, outside the submitted work. CSLC has received grants from the Food and Health Bureau of the Government of the Hong Kong Special Administrative Region, Hong Kong Research Grant Council, Hong Kong Innovation and Technology Commission, Pfizer, IQVIA, and Amgen; and personal fees from PrimeVigilance; outside the submitted work. XL has received research grants from the Food and Health Bureau of the Government of the Hong Kong Special Administrative Region; research and educational grants from Janssen and Pfizer; internal funding from the University of Hong Kong; and consultancy fees from Merck Sharp & Dohme, unrelated to this work. ICKW reports research funding from Amgen, Bristol Myers Squibb, Pfizer, Janssen, Bayer, GSK, Novartis, the Hong Kong Research Grants Council, the Hong Kong Health and Medical Research Fund, the National Institute for Health Research in England, the European Commission, and the National Health and Medical Research Council in Australia, outside the submitted work; and is a non-executive director of Jacobson Medical in Hong Kong and a consultant to IQVIA and World Health Organization. EWC reports grants from Research Grants Council (RGC, Hong Kong), Research Fund Secretariat of the Food and Health Bureau, National Natural Science Fund of China, Wellcome Trust, Bayer, Bristol-Myers Squibb, Pfizer, Janssen, Amgen, Takeda, and Narcotics Division of the Security Bureau of the Hong Kong Special Administrative Region; honorarium from Hospital Authority; outside the submitted work.