SARS-CoV-2 is the global, quickly extending virus causing a koronavirusny disease 2019 (COVID-19). The current strategy in public health care directed to mitigation of the consequences of transmission of infection include fast identification of cases of infection, isolation, tracking of contacts and self-isolation of the persons which underwent infection. After the person contacts to a virus, observation and a quarantine during a 14-day incubation interval are standard practice. So far no drugs were found to prevent a SARS-CoV-2 broadcast.
Both chloroquine, and hydroxychloroquine, derivative of it, have in vitro activity against SARS-CoV and SARS-CoV-2. It is considered that hydroxychloroquine interferes with glycosylation of a receptor of angiotensin-converting enzyme-2 (ACE2) which is the place of binding for a glycoprotein of thorns of a viral envelope and as it was shown, inhibits function endolisozy. Besides, hydroxychloroquine can have higher level of activity against SARS-CoV-2, than chloroquine.
The majority of clinical trials of chloroquine or hydroxychloroquine for treatment of COVID-19 was devoted to the hospitalized patients. However to change dynamics of epidemic, it is necessary to break off a chain of its distribution. The risk of secondary transmission of infection in house conditions is 10-15%. Small, nonrandomized, uncontrollable cohort researches allow to assume that use of hydroxychloroquine can reduce or even to eliminate this risk. Remains to unknown whether hydroxychloroquine in high doses in the short term will be able to prevent a disease after contact of high risk.
The research in the USA and a part of Canada with any choice in the conditions of double anonymity with control on placebo which tested hydroxychloroquine as post-contact prophylactic was conducted. Authors of a research assumed that hydroxychloroquine can be potentially used as post-contact prevention for prevention of a symptomatic infection after contact with the carrier of COVID-19. In a research registered adults who had household contact or contact in a workplace with the people infected with COVID-19 at distance less than 183 cm and more than 10 min. on which there was neither mask, nor goggles (contact of high risk) or on whom there was a mask, but there were no goggles (contact of average risk). Participants of a research were recruited generally by means of social networks and also traditional media platforms. Participants more young than 18 years or which were hospitalized and also people who got under other criteria of an exception of participation were not accepted. Persons with symptoms of COVID-19 or with the confirmed PTsR on SARS-CoV-2, were also excluded from this research.
Within 4 days after contact by the participant either placebo-drug, or hydroxychloroquine were randomly appointed (800 mg once, then 600 mg within 6–8 hours, then 600 mg a day within 4 additional days). During the examination conducted within 4-6 weeks questions of any subsequent inspections, diseases or hospitalization were set. Existence of laboratory confirmed COVID-19 or the disease comparable to COVID-19, within 14 days was the main considered result.
Was it is registered 821 patients. In total 87.6% of participants (719 of 821) reported about contact of high risk with infected with COVID-19. The number of the new diseases comparable to COVID-19 did not differ essentially. Side effects were more characteristic of hydroxychloroquine, than of placebo, however no serious side reactions were noted.
Discussing results of a research, authors note that in this test high doses of hydroxychloroquine did not prevent a disease. The approach to set of participants in a research undertaken by authors led to the fact that participants were, as a rule, younger and healthier than those who were exposed to risk of COVID-19 most. Though it is impossible to exclude possible results from prevention in group of the increased risk (that is more age participants), the possible risks connected with hydroxychloroquine use can become higher.
Thus, this randomized test did not show essential advantage of hydroxychloroquine as post-contact prevention of COVID-19. The question of whether there will be such prevention effective in the groups of the population subject to high risk, is a separate subject for researches.