Incidence of COVID-19 in patients exposed to chloroquine and hydroxychloroquine: results from a population-based prospective cohort in Catalonia, Spain, 2020

3/9 Pre-Exposure Prophylaxis study (treated before exposed to the virus)

Vivanco-Hidalgo et al., Eurosurveillance, doi:/10.2807/1560-7917.ES.2021.26.9.2001202 (Peer Reviewed)
Incidence of COVID-19 in patients exposed to chloroquine and hydroxychloroquine: results from a population-based prospective cohort in Catalonia, Spain, 2020

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Retrospective database analysis of chronic HCQ users and matched control patients, failing to match or adjust for the very different baseline risk for systemic autoimmune disease patients. Other research shows that the risk of COVID-19 for systemic autoimmune disease patients is much higher overall, Ferri et al. show OR 4.42, p<0.001 [1].

Vivanco-Hidalgo et al., 3/9/2021, retrospective, Spain, Europe, peer-reviewed, 8 authors.

risk of hospitalization, 46.0% higher, RR 1.46, p = 0.10, treatment 40 of 6746 (0.6%), control 50 of 13492 (0.4%), adjusted per study.

risk of COVID-19 case, 8.0% higher, RR 1.08, p = 0.50, treatment 97 of 6746 (1.4%), control 183 of 13492 (1.4%), adjusted per study.

This study is excluded in meta analysis: not fully adjusting for the different baseline risk of systemic autoimmune patients.

Effect extraction follows pre-specified rules prioritizing more serious outcomes. For an individual study the most serious outcome may have a smaller number of events and lower statistical signficance, however this provides the strongest evidence for the most serious outcomes when combining the results of many trials.

[1] c19study.com/ferri.html

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