RESUMO
The international tourist destination of Bali reported its first case of Coronavirus Disease 2019 or COVID-19 in March 2020. To better understand the extent of exposure of Bali's 4.3 million inhabitants to the COVID-19 virus, we performed two repeated cross-sectional serosurveys stratified by urban and rural areas. We used a highly specific multiplex assay that detects antibodies to three different viral antigens. We also assessed demographic and social risk factors and history of symptoms. Our results show that the virus was widespread in Bali by late 2020, with 16.73% (95% CI 12.22-21.12) of the population having been infected by that time. We saw no differences in seroprevalence between urban and rural areas, possibly due to extensive population mixing, and similar levels of seroprevalence by gender and among age groups, except for lower seroprevalence in the very young. We observed no difference in seroprevalence between our two closely spaced surveys. Individuals reporting symptoms in the past six months were about twice as likely to be seropositive as those not reporting symptoms. Based upon official statistics for laboratory diagnosed cases for the six months prior to the survey, we estimate that for every reported case an additional 52 cases, at least, were undetected. Our results support the hypothesis that by late 2020 the virus was widespread in Bali, but largely undetected by surveillance.
RESUMO
OBJECTIVE: The aim of this study was to compare the coverage of Japanese encephalitis (JE) immunization obtained from a recall survey and immunization registers at community health centers (CHCs) in Bali Province, Indonesia. METHODS: A population-based survey was conducted, and random 2-staged selection of clusters of sub-villages was performed. The sample consisted of households with children aged 9 months to 15 years old. Interviews were carried out with carers to recall JE immunization status. The recall immunization status was considered valid when name, date, and confirmation of immunization were available in an immunization register at a CHC. Descriptive analysis was performed. The completeness of the information within immunization registers at CHCs was assessed. RESULTS: The coverage of JE immunization obtained from the recall survey was 93.8% (95% confidence interval [CI], 92.8-94.9). It decreased to 74.9% (95% CI, 72.8-77.2) after being validated against immunization registers. The recall coverage of JE immunization was significantly higher than immunization register data suggested. This discrepancy varied from 6.5% to 36.4% across 6 districts; however, none of these districts achieved the recommended target coverage of 95%. The quality of immunization registers varied across CHCs. CONCLUSION: The use of an immunization register may result in underestimating the true coverage of vaccination programs, and its utilization for measuring immunization coverage requires further consideration.
