The impacts of long COVID and booster doses of post-infection vaccination among hospital-discharged COVID-19 survivors in Hong Kong: A retrospective observational study

Abstract

Background: This study examined the prevalence of long COVID, risk factors, vaccination status, and health-related quality of life in hospital-discharged individuals with a history of COVID-19 infection in Hong Kong.

Methods: This is a retrospective observational study. A convenience sampling was used to recruit individuals with a history of COVID-19 infection from a university teaching hospital in Hong Kong. 717 out of 1771 individuals aged 18 years or above with COVID-19 infection (confirmed by polymerase chain reaction/rapid antigen test) and hospitalized during the COVID-19 outbreak completed the telephone follow-up between January 2023 and March 2025. The prevalence of long COVID (defined by the WHO), risk factors, vaccination status, and health-related quality of life were analyzed. The proportions were weighted by the sex and age distribution of Hong Kong adults in 2023.

Results: The mean age of participants was 46.8 years (±17.4), and 67.4 % were men. The most prevalent long COVID symptoms were shortness of breath (10.8 %), persistent fatigue (9.8 %), forgetfulness (9.5 %), and persistent dry cough (4.3 %). 52.3 % of participants received three vaccine doses after contracting COVID-19, and 71.3 % of them received BioNTech. Participants who experienced shortness of breath, persistent fatigue, and forgetfulness had poorer health-related quality of life, as indicated by lower scores on the EuroQol-visual analog scales and the Physical and Mental Component Scores of the VR-12 (all P < 0.05). Participants who received booster doses (at least three doses) were associated with lower odds of experiencing long COVID symptoms, including shortness of breath, persistent fatigue, forgetfulness, and persistent dry cough (all P < 0.05).

Conclusions: The prevalence of long COVID was low among the hospital-discharged individuals, and booster doses of post-infection vaccination might reduce the risk of experiencing these symptoms. Further investigation is needed to examine the underlying mechanisms of long COVID and how these risks can be mitigated.

Keywords: Booster doses; COVID-19 survivors; Hospital discharged individuals; Long COVID; Post-infection vaccination.