Assessing COVID-19 Vaccine Effectiveness in Frail Long-Term Care Facilities Residents in a Middle-Income Country (preprint)

ABSTRACT

Background: During the COVID-19 pandemic, individuals residing in long-term care facilities (LTCF) are particularly vulnerable to adverse outcomes due to their higher rates of frailty, disabilities, cognitive impairment, dementia, and chronic illnesses. In low and middle-income nations, research on immunizing frail populations is lacking, while most studies on COVID-19 in LTCF come from wealthier nations and may not fully capture the situation in emerging countries.  Methods: We aimed to evaluate the effectiveness of first, second and third COVID-19 vaccine doses, against infections, hospitalizations, and deaths, and their association with frailty, age, sex and chronic disease, among older adults, in a social vulnerability context. This retrospective cohort study, comprises a total of 712 older adults, in a social vulnerability context, of 29 LTCF, in Brazil. Continuous variables were described by medians and interquartile ranges and categorical variables were represented by absolute and relative frequencies. The Mann-Whitney test was used. For evaluating the relation between categorical variables, Pearson's chi-square test was used. When comparing proportions, the Z test of proportion was applied. A significance level of 5% was considered.  Results: Median age was 81.37 years, 72.8% were female, 94.61% were frail, 79.97% had a cognitive impairment, 69.54% had a mobility impairment, 78.37% have, at least, one chronic disease and 72.73% use five or more medications per day. Before the vaccine, mobility impairment was associated with great contamination rates (p=.03); frailty (p=.02) and previous pulmonary disease (p=.03) with symptoms of gravity; frailty (p=.02), pulmonary disease (p=.04) and male sex (p=.02) with emergency care or hospital admission. After the third vaccine dose, only frailty remains associated with admissions (p=.03). The number of positive cases (p=.001), symptomatic patients (p<.001), admissions (p=.001) and deaths (p<.001) were substantially reduced after the three vaccine doses.  Conclusions and Implications Even in a frail population, the vaccine was effective, in the reduction of positive cases, the number of symptomatic patients, admission to emergency or hospital care and deaths. Before the vaccine, frailty, previous pulmonary disease and male sex were associated with worse outcomes. After the vaccine, frailty remains associated with a major number of admissions.