A randomized clinical trial published in "International Journal of Infectious Diseases" portrayed that taking the combination of zinc and doxycycline has a protective or prophylactic effect against coronavirus infection. Researchers sought to examine the effectiveness and safety of doxycycline (100 mg/day) plus zinc (15 mg/day) to prevent COVID-19 in comparison with two control groups.

In this prospective double-blind study, doxycycline plus zinc given together as a preventative medication was compared with doxycycline given alone versus placebo. The efficacy of preventive therapy was estimated by a reduction in the number of cases of coronavirus disease and/or reduction in the viral load assessed by SARS-CoV-2 cycle threshold value with the aid of RT-PCR tests.

In comparison to the other individuals, there was a substantial drop in SARS-CoV-2 infection in the group that received both doxycycline and zinc. The risk of coronavirus infection was not linked with other comorbidities like diabetes, chronic obstructive pulmonary disorder, asthma, and hypertension. Doxycycline in combination with zinc therapy displayed minimal adverse effects. Hence, using doxycycline and zinc as a potential treatment appears to be beneficial for the primary prevention of COVID-19.