Increasing ventilation reduces SARS-CoV-2 airborne transmission in schools: A retrospective cohort study in Italy's Marche region.
Level 3 - non-randomized controlled study
Retrospective non-randomized controlled cohort study
PubMed 36568748 · doi:10.3389/fpubh.2022.1087087
What was done
A retrospective cohort study analyzed SARS-CoV-2 transmission among students across more than 10,000 classrooms in Italy's Marche region, comparing 316 classrooms equipped with mechanical ventilation against those with natural ventilation alone. Ordinary and logistic regression models were used to estimate the relative risk of infection associated with classroom exposure and ventilation rates.
What was found
Classrooms equipped with mechanical ventilation systems showed at least a 74% reduction in the relative risk of student infection compared with natural ventilation alone, reaching at least an 80% reduction for ventilation rates exceeding 10 L s⁻¹ student⁻¹. Regression models indicated a 12% to 15% relative risk reduction for each additional unit of ventilation rate per person.
Why it matters
It provides real-world observational evidence that mechanical ventilation substantially lowers school-based airborne transmission of SARS-CoV-2, supporting specific ventilation targets above baseline indoor air standards.
Limits
The study is retrospective and observational, making it vulnerable to residual confounding (such as student masking compliance, socio-economic factors, or out-of-school exposures). Mechanical ventilation was present in only 316 of >10,000 classrooms, and the abstract lacks exact student participant counts and confidence intervals.
Cited by
- contradicts Viruses can only be transmitted between humans through physical touch and cannot survive outside the human body.