Masks: meta-analysis of COVID-19 studies

Meta-analysis of masks COVID-19 studies. Only RCTs are included.
All studies   Cases   RCTs   Peer-reviewed   All outcomes  
0 0.5 1 1.5+ All studies 2% 4 350K Improvement, Studies, Patients Relative Risk Cases 2% 4 350K RCTs 2% 4 350K Prophylaxis 2% 4 350K Masks for COVID-19 c19early.org December 2025 Favorsmasks Favorscontrol
0 0.25 0.5 0.75 1 1.25 1.5 1.75 2+ DANMASK-19 Bundgaard (RCT) 18% 0.82 [0.54-1.23] cases 42/2,392 53/2,470 Improvement, RR [CI] Treatment Control Abaluck (RCT) 9% 0.91 [0.81-0.99] symp. case 178,322 (n) 163,861 (n) TRACE/STOPCOV Smith (SB RCT) -98% 1.98 [0.97-4.03] cases 137 (n) 108 (n) Solberg (RCT) -7% 1.07 [0.58-1.96] cases 21/1,834 21/1,967 Tau​2​ = 0.03, I​2​ = 41.5%, p = 0.87 Prophylaxis 2% 0.98 [0.76-1.25] 63/182,685 74/168,406 2% lower risk All studies 2% 0.98 [0.76-1.25] 63/182,685 74/168,406 2% lower risk 4 masks COVID-19 studies c19early.org December 2025 Tau​2​ = 0.03, I​2​ = 41.5%, p = 0.87 Effect extraction pre-specified(most serious outcome) Favors masks Favors control 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2+ DANMASK-19 Bundgaard (RCT) 18% 0.82 [0.54-1.23] cases 42/2,392 53/2,470 Improvement, RR [CI] Treatment Control Abaluck (RCT) 9% 0.91 [0.81-0.99] symp. case 178,322 (n) 163,861 (n) TRACE/STOPCOV Smith (SB RCT) -98% 1.98 [0.97-4.03] cases 137 (n) 108 (n) Solberg (RCT) -7% 1.07 [0.58-1.96] cases 21/1,834 21/1,967 Tau​2​ = 0.03, I​2​ = 41.5%, p = 0.87 Prophylaxis 2% 0.98 [0.76-1.25] 63/182,685 74/168,406 2% lower risk All studies 2% 0.98 [0.76-1.25] 63/182,685 74/168,406 2% lower risk 4 masks COVID-19 case results c19early.org December 2025 Tau​2​ = 0.03, I​2​ = 41.5%, p = 0.87 Favors masks Favors control 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2+ DANMASK-19 Bundgaard (RCT) 18% 0.82 [0.54-1.23] cases 42/2,392 53/2,470 Improvement, RR [CI] Treatment Control Abaluck (RCT) 9% 0.91 [0.81-0.99] symp. case 178,322 (n) 163,861 (n) TRACE/STOPCOV Smith (SB RCT) -98% 1.98 [0.97-4.03] cases 137 (n) 108 (n) Solberg (RCT) -7% 1.07 [0.58-1.96] cases 21/1,834 21/1,967 Tau​2​ = 0.03, I​2​ = 41.5%, p = 0.87 Prophylaxis 2% 0.98 [0.76-1.25] 63/182,685 74/168,406 2% lower risk All studies 2% 0.98 [0.76-1.25] 63/182,685 74/168,406 2% lower risk 4 masks COVID-19 Randomized Controlled Trials c19early.org December 2025 Tau​2​ = 0.03, I​2​ = 41.5%, p = 0.87 Effect extraction pre-specified(most serious outcome) Favors masks Favors control 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2+ DANMASK-19 Bundgaard (RCT) 18% 0.82 [0.54-1.23] cases 42/2,392 53/2,470 Improvement, RR [CI] Treatment Control Abaluck (RCT) 9% 0.91 [0.81-0.99] symp. case 178,322 (n) 163,861 (n) TRACE/STOPCOV Smith (SB RCT) -98% 1.98 [0.97-4.03] cases 137 (n) 108 (n) Solberg (RCT) -7% 1.07 [0.58-1.96] cases 21/1,834 21/1,967 Tau​2​ = 0.03, I​2​ = 41.5%, p = 0.87 Prophylaxis 2% 0.98 [0.76-1.25] 63/182,685 74/168,406 2% lower risk All studies 2% 0.98 [0.76-1.25] 63/182,685 74/168,406 2% lower risk 4 masks COVID-19 peer reviewed studies c19early.org December 2025 Tau​2​ = 0.03, I​2​ = 41.5%, p = 0.87 Effect extraction pre-specified(most serious outcome) Favors masks Favors control 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2+ DANMASK-19 Bundgaard (RCT) 18% 0.82 [0.54-1.23] cases 42/2,392 53/2,470 Improvement, RR [CI] Treatment Control Abaluck (RCT) 9% 0.91 [0.81-0.99] symp. case 178,322 (n) 163,861 (n) TRACE/STOPCOV Smith (SB RCT) -98% 1.98 [0.97-4.03] cases 137 (n) 108 (n) TRACE/STOPCOV Smith (SB RCT) -58% 1.58 [0.29-8.45] cases 4/137 2/108 TRACE/STOPCOV Smith (SB RCT) -164% 2.64 [0.89-7.80] misc. 137 (n) 108 (n) TRACE/STOPCOV Smith (SB RCT) -373% 4.73 [0.58-38.7] misc. 6/137 1/108 TRACE/STOPCOV Smith (SB RCT) -176% 2.76 [0.58-13.0] misc. 7/137 2/108 TRACE/STOPCOV Smith (SB RCT) -358% 4.58 [0.22-94.3] misc. 2/137 0/108 TRACE/STOPCOV Smith (SB RCT) 69% 0.31 [0.01-7.44] misc. 0/137 1/108 Solberg (RCT) -7% 1.07 [0.58-1.96] cases 21/1,834 21/1,967 Masks COVID-19 outcomes c19early.org December 2025 Favors masks Favors control