Smoking: meta-analysis of COVID-19 studies

All studies Mortality Serious outcomes Cases Peer-reviewed Long COVID All outcomes

Outcome (studies)

Improvement

Relative risk · 95% CI

All studies (6)−61%

Mortality (1)3%

Cases (4)−118%

Peer-reviewed (5)−86%

Prophylaxis (5)−49%

Early (1)−134%

00.511.5+

← Smoking
reduces riskIncreased
risk →

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c19early.org

October 2026

Smoking COVID-19 studies

StudyImprovementRR · 95% CIOutcomeTreatmentControlRelative Risk

Mockeliunas−134%2.34 · 1.54–3.52cases274 (n)726 (n)

Early treatment−134%2.34 · 1.55–3.53274 (n)726 (n)134% higher risk

Tau² = 0.00, I² = 0.0%, p < 0.0001

Razjouyan3%0.97 · 0.78–1.22death1,082 (n)3,352 (n) Paul37%0.63 · 0.32–1.16PASC1,811 (all patients)LONG COVID Montini−270%3.70 · 2.04–6.67casescase-control study Akbar−82%1.82 · 1.47–2.27cases1,866 (n)8,134 (n) Pavlidou−72%1.72 · 1.49–1.96cases3,345 (n)1,852 (n)

Prophylaxis−49%1.49 · 0.93–2.386,293 (n)13,338 (n)49% higher risk

Tau² = 0.24, I² = 89.2%, p = 0.098

All studies−61%1.61 · 1.06–2.446,567 (n)14,064 (n)61% higher risk

Tau² = 0.23, I² = 88.1%, p = 0.02600.511.52+

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← Smoking
reduces riskSmoking
increases risk →

c19early.org

October 2026

Smoking COVID-19 mortality results

StudyImprovementRR · 95% CITreatmentControlRelative Risk

Razjouyan3%0.97 · 0.78–1.221,082 (n)3,352 (n)

Prophylaxis3%0.97 · 0.78–1.211,082 (n)3,352 (n)3% lower risk

Tau² = 0.00, I² = 0.0%, p = 0.8

All studies3%0.97 · 0.78–1.211,082 (n)3,352 (n)3% lower risk

Tau² = 0.00, I² = 0.0%, p = 0.800.511.52+

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← Smoking
reduces riskSmoking
increases risk →

c19early.org

October 2026

Smoking COVID-19 serious outcomes

StudyImprovementRR · 95% CIOutcomeTreatmentControlRelative Risk

Razjouyan3%0.97 · 0.78–1.22death1,082 (n)3,352 (n) Paul37%0.63 · 0.32–1.16PASC1,811 (all patients)LONG COVID

Prophylaxis14%0.86 · 0.59–1.261,082 (n)3,352 (n)14% lower risk

Tau² = 0.04, I² = 40.4%, p = 0.45

All studies14%0.86 · 0.59–1.261,082 (n)3,352 (n)14% lower risk

Tau² = 0.04, I² = 40.4%, p = 0.4500.511.52+

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← Smoking
reduces riskSmoking
increases risk →

c19early.org

October 2026

Smoking COVID-19 case results

StudyImprovementRR · 95% CIOutcomeTreatmentControlRelative Risk

Mockeliunas−134%2.34 · 1.54–3.52cases274 (n)726 (n)

Early treatment−134%2.34 · 1.55–3.53274 (n)726 (n)134% higher risk

Tau² = 0.00, I² = 0.0%, p < 0.0001

Montini−270%3.70 · 2.04–6.67casescase-control study Akbar−82%1.82 · 1.47–2.27cases1,866 (n)8,134 (n) Pavlidou−72%1.72 · 1.49–1.96cases3,345 (n)1,852 (n)

Prophylaxis−118%2.18 · 1.44–3.285,211 (n)9,986 (n)118% higher risk

Tau² = 0.09, I² = 69.9%, p = 0.00024

All studies−118%2.18 · 1.62–2.945,485 (n)10,712 (n)118% higher risk

Tau² = 0.05, I² = 58.2%, p < 0.000100.511.52+

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← Smoking
reduces riskSmoking
increases risk →

c19early.org

October 2026

Smoking COVID-19 peer reviewed studies

StudyImprovementRR · 95% CIOutcomeTreatmentControlRelative Risk

Mockeliunas−134%2.34 · 1.54–3.52cases274 (n)726 (n)

Early treatment−134%2.34 · 1.55–3.53274 (n)726 (n)134% higher risk

Tau² = 0.00, I² = 0.0%, p < 0.0001

Razjouyan3%0.97 · 0.78–1.22death1,082 (n)3,352 (n) Montini−270%3.70 · 2.04–6.67casescase-control study Akbar−82%1.82 · 1.47–2.27cases1,866 (n)8,134 (n) Pavlidou−72%1.72 · 1.49–1.96cases3,345 (n)1,852 (n)

Prophylaxis−77%1.77 · 1.08–2.906,293 (n)13,338 (n)77% higher risk

Tau² = 0.22, I² = 89.9%, p = 0.024

All studies−86%1.86 · 1.22–2.856,567 (n)14,064 (n)86% higher risk

Tau² = 0.20, I² = 88.2%, p = 0.004400.511.52+

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← Smoking
reduces riskSmoking
increases risk →

c19early.org

October 2026

Smoking COVID-19 long COVID results

StudyImprovementRR · 95% CIOutcomeTreatmentControlRelative Risk

Paul37%0.63 · 0.32–1.16PASC1,811 (all patients)

Prophylaxis37%0.63 · 0.34–1.1637% lower risk

Tau² = 0.00, I² = 0.0%, p = 0.14

All studies37%0.63 · 0.34–1.1637% lower risk

Tau² = 0.00, I² = 0.0%, p = 0.1400.511.52+

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← Smoking
reduces riskSmoking
increases risk →

c19early.org

October 2026

Smoking COVID-19 outcomes

StudyImprovementRR · 95% CIOutcomeTreatmentControlRelative Risk

Mockeliunas−134%2.34 · 1.54–3.52cases274 (n)726 (n) Razjouyan3%0.97 · 0.78–1.22death1,082 (n)3,352 (n) Razjouyan−16%1.16 · 1.01–1.32death4,494 (n)3,352 (n) Paul37%0.63 · 0.32–1.16PASC1,811 (all patients)LONG COVID Montini−270%3.70 · 2.04–6.67casescase-control study Akbar−82%1.82 · 1.47–2.27cases1,866 (n)8,134 (n) Pavlidou−72%1.72 · 1.49–1.96cases3,345 (n)1,852 (n)

00.511.52+

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← Smoking
reduces riskSmoking
increases risk →