Rapid communication Open Access
Like 0


The mRNA vaccine Comirnaty and the inactivated vaccine CoronaVac are both available in Hong Kong’s COVID-19 vaccination programme. We observed waning antibody levels in 850 fully vaccinated (at least 14 days passed after second dose) blood donors using ELISA and surrogate virus neutralisation test. The Comirnaty-vaccinated group’s (n = 593) antibody levels remained over the ELISA and sVNT positive cut-offs within the first 6 months. The CoronaVac-vaccinated group’s (n = 257) median antibody levels began to fall below the cut-offs 4 months after vaccination.


Article metrics loading...

Loading full text...

Full text loading...



  1. The Government of Hong Kong Special Administrative Region. Hong Kong vaccination dashboard. Hong Kong: The Government of Hong Kong Special Administrative Region; 2021. [Accessed: 5 Dec 2021]. Available from: https://www.covidvaccine.gov.hk/en/dashboard/
  2. Perera RA, Mok CK, Tsang OT, Lv H, Ko RL, Wu NC, et al. Serological assays for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), March 2020. Euro Surveill. 2020;25(16):2000421.  https://doi.org/10.2807/1560-7917.ES.2020.25.16.2000421  PMID: 32347204 
  3. Perera RAPM, Ko R, Tsang OTY, Hui DSC, Kwan MYM, Brackman CJ, et al. Evaluation of a SARS-CoV-2 surrogate virus neutralization test for detection of antibody in human, canine, cat, and hamster sera. J Clin Microbiol. 2021;59(2):e02504-20.  https://doi.org/10.1128/JCM.02504-20  PMID: 33139421 
  4. Mallapaty S. China’s COVID vaccines have been crucial - now immunity is waning. Nature. 2021;598(7881):398-9.  https://doi.org/10.1038/d41586-021-02796-w  PMID: 34650240 
  5. World Health Organization (WHO). WHO validates Sinovac COVID-19 vaccine for emergency use and issues interim policy recommendations. Geneva: WHO; 2021. [Accessed: 13 Jan 2022]. Available from: https://www.who.int/news/item/01-06-2021-who-validates-sinovac-covid-19-vaccine-for-emergency-use-and-issues-interim-policy-recommendations
  6. Your Europe. Travel and covid: rules and restrictions. Brussels: Your Europe; 2022. [Accessed: 13 Jan 2022]. Available from: https://europa.eu/youreurope/citizens/travel/travel-and-covid/index_en.htm
  7. European Council. COVID-19: travel into the EU. Brussels: European Council 2022. [Accessed: 13 Jan 2022]. Available from: https://www.consilium.europa.eu/en/policies/coronavirus/covid-19-travel-into-the-eu/
  8. Zee JST, Lai KTW, Ho MKS, Leung ACP, Fung LH, Luk WP, et al. Serological response to mRNA and inactivated COVID-19 vaccine in healthcare workers in Hong Kong: decline in antibodies 12 weeks after two doses. Hong Kong Med J. 2021;27(5):380-3. PMID: 34657837 
  9. Pan H, Wu Q, Zeng G, Yang J, Jiang D, Deng X, et al. Immunogenicity and safety of a third dose, and immune persistence of CoronaVac vaccine in healthy adults aged 18-59 years: interim results from a double-blind, randomized, placebo-controlled phase 2 clinical trial. medRxiv. 2021:2021.07.23.21261026. Preprint . https://doi.org/10.1101/2021.07.23.21261026 
  10. Khoury DS, Cromer D, Reynaldi A, Schlub TE, Wheatley AK, Juno JA, et al. Neutralizing antibody levels are highly predictive of immune protection from symptomatic SARS-CoV-2 infection. Nat Med. 2021;27(7):1205-11.  https://doi.org/10.1038/s41591-021-01377-8  PMID: 34002089 
  11. Cromer D, Steain M, Reynaldi A, Schlub TE, Wheatley AK, Juno JA, et al. Neutralising antibody titres as predictors of protection against SARS-CoV-2 variants and the impact of boosting: a meta-analysis. Lancet Microbe. 2022;3(1):e52-61.  https://doi.org/10.1016/S2666-5247(21)00267-6  PMID: 34806056 
  12. Chen Y, Yin S, Tong X, Tao Y, Ni J, Pan J, et al. Dynamic SARS-CoV-2-specific B-cell and T-cell responses following immunization with an inactivated COVID-19 vaccine. Clin Microbiol Infect. 2021;S1198-743X(21)00605-4.  PMID: 34715346 
  13. Geers D, Shamier MC, Bogers S, Hartog Gd, Gommers L, Nieuwkoop NN, et al. SARS-CoV-2 variants of concern partially escape humoral but not T-cell responses in COVID-19 convalescent donors and vaccinees. Sci Immunol. 2021;6(59):eabj1750.
  14. Sahin U, Muik A, Vogler I, Derhovanessian E, Kranz LM, Vormehr M, et al. BNT162b2 vaccine induces neutralizing antibodies and poly-specific T cells in humans. Nature. 2021;595(7868):572-7.  https://doi.org/10.1038/s41586-021-03653-6  PMID: 34044428 
  15. Hicks SM, Pohl K, Neeman T, McNamara HA, Parsons KM, He JS, et al. , SARS-CoV-2 Testing in Elective Surgery Collaborators. SARS-CoV-2 Testing in Elective Surgery Collaborators. A dual-antigen enzyme-linked immunosorbent assay allows the assessment of severe acute respiratory syndrome coronavirus 2 antibody seroprevalence in a low-transmission setting. J Infect Dis. 2021;223(1):10-4.  https://doi.org/10.1093/infdis/jiaa623  PMID: 33009908 
  16. Samineni S, Parvataneni S, Kelly C, Gangur V, Karmaus W, Brooks K. Optimization, comparison, and application of colorimetric vs. chemiluminescence based indirect sandwich ELISA for measurement of human IL-23. J Immunoassay Immunochem. 2006;27(2):183-93.  https://doi.org/10.1080/15321810600573051  PMID: 16711255 

Data & Media loading...

Supplementary data

Submit comment
Comment moderation successfully completed
This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error