Identification of exposure, other treatments and covariates and
the matching procedure
Exposure/non-exposure to fluvoxamine was identified based on timing of
prescriptions with the respective ATC code (N06AB08) relative to the
index COVID-19 diagnosis. All other psychiatric and other treatments
required for identification of patient subsets and covariate matching
are listed in Appendix, Table A1. We implemented exact matching using
package MatchIt 14 in R15. For
all contrasts (Group A vs. B, A vs. C and B vs. C), patients were
matched in respect to age, sex, vaccination status (type of vaccine and
timing relative to the index COVID-19 episode), calendar period of
COVID-19 diagnosis, and a range of comorbidities and pharmacological
treatments (detailed in Table 2). For the Group A vs. Group B
comparisons, additional matching included also psychiatric diagnoses
(Table 2). Comparisons vs. Group C patients did not include these
covariates, since Group C patients were free of psychiatric conditions
(by definition). Identification of all comorbidities used for matching
is detailed in Appendix, Table A2-Table A4, and section on
immunocompromised and diabetic patients.