Objective:
To investigate polymerase chain reaction (PCR) confirmed symptomatic coronavirus disease-2019 (COVID-19) infection incidence in vaccinated older adults.
Materials and Methods:
This prospective study comprised 483 adults aged 60 years and older, all vaccinated with 2 doses of inactivated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine. All participants had their anti-SARS-CoV-2 immunoglobulin G antibody titers checked and were simultaneously evaluated by comprehensive geriatric assessment, including frailty. We defined the overall survival time as the period from the date of blood collection for antibody responses through the event date [i.e., PCR confirmed (COVID-19) diagnosis] (if any), the time of the last visit or at the termination of data collection (November 25, 2021), whichever occurred first. Individuals who were vaccinated with the 3rd dose of any type were censored at the time of vaccination and removed from further follow-up.
Results:
The incidence of symptomatic COVID-19 was significantly higher in the frail group, with a cumulative incidence of 7.1% and 2.2% in the frail and non-frail groups, respectively (p=0.02). In Cox regression analysis, the clinical frailty scale (CFS) score was found to be a significant predictor for breakthrough COVID-19 infection [hazard ratio =3.2 (95% confidence interval =1.0-9.9), p=0.04].
Conclusion:
High CFS scores among vaccinated older adults should be considered as an easy-to-assess, high-risk marker for predicting breakthrough COVID-19 infection.
Keywords: SARS-CoV-2, Sinovac, CoronaVac, older people, frailty