• immune system diseases
• autoantibodies
• autoimmunity

We thank the readers who share interesting ideas on our publication entitled ‘SLE, hydroxychloroquine and no SLE patients with COVID-19: a comment’.1 First, we really appreciate the reply by Monti and Montecucco.2 We agree that large registry data are required to clarify the incidence of COVID-19 in patients with systemic lupus erythematosus (SLE).1 Seeking for a new drug against the emerging COVID-19 is a challenge. In this pandemic situation, urgent search for drug and vaccine is necessary. Not only hydroxychloroquine but also other drugs such as antiretroviral drugs are widely used without complete clinical trials. We feel glad that our article can stimulate data sharing on the important issue of the inter-relationship between COVID-19, SLE and hydroxychloroquine. Additional correspondences by Sawalha,3 Romão et al 4 and Goyal5 are examples of new data. At the time our correspondence with Monti and Montecucco’s1 paper was prepared and submitted, there were no publications on the existence of COVID-19 in patients with SLE. All the SLE cases in the correspondences are new cases reported after we first proposed a hypothesis. The proposed idea was a possible explanation of the data at that time. In science, new findings might or might not support the hypothesis. The correspondences to our article refer to registry data that were published after our article (we submitted our correspondence/comment on 31 March 2020, and our article was published on 15 April 2020 and the registry data published on 16 April 2020). Therefore, our first hypothesis was not based on the unpublished registry data at that time. With the increasing number of COVID-19 cases globally, more than one million patients, there may now be new data on SLE patients with COVID-19. We hereby acknowledge contributions that COVID-19 does occur in patients with SLE. At present, the efficacy or lack of efficacy of hydroxychloroquine remains a speculation in the absence of trials, and although the efficacy of hydroxychloroquine still requires further scientific proof the drug has been widely used in the current COVID-19 outbreak situation.6 Further systematic evaluation on the benefits of this drug is required. Hydroxychloroquine is not recommended for use in the prevention of COVID-19 in healthy people. Our article did not recommend the drug for COVID-19 prevention. There may now be reports of SLE patients with COVID-19, but an important consideration is whether or not these patients received hydroxychloroquine. A recent report on the first few SLE patients with COVID-19 showed that hydroxychloroquine at standard dose could not help prevent severe COVID-19.7 If hydroxychloroquine has a pharmacological effect against COVID-19, dosage of this drug that can effectively counteract the infection remains unknown.