Need for abundant caution in prophylactic application of chloroquine and hydroxychloroquine for viral infections including COVID-19: Possibility of increased susceptibility

Abstract

Significant interest in application of Chloroquine (CQ) and Hydroxychloroquine (HCQ) for prophylaxis and treatment of COVID-19 has been recently reported throughout the world. In the light of this, it has become important to revisit the mechanisms of action, as well as clinical evidence for efficacy of CQ and HCQ in similar viral infections. We note that while some evidence exists for therapeutic efficacy of CQ and HCQ in mitigating morbidities associated with virus-induced inflammation and immuno-hyperactivity, abundant caution is necessary in expecting prophylactic efficacy in the light of therapeutic evidence. In particular, we intend to draw urgent attention to the fact that the same immuno-suppresive and immuno-modulatory properties of CQ and HCQ which render them useful as therapeutic agents in viral pneumonia and cytokine storm syndrome, are also expected to make them dangerous prophylactic agents against viral infections. We also intend to draw attention to some other potential concerns associated with widespread prophylactic usage of CQ and HCQ.