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Research > Briefing - Vaccines, variants and ventilation

Research briefing: Vaccines, variants, and ventilation

16 December 2021

This final research briefing, prepared by researchers at Battelle, is intended to provide timely information about SARS-CoV-2 vaccines and variants to libraries, archives, museums (LAMs), and their stakeholders. This is a review of scientific literature published through 29 November 2021, and should be used in conjunction with other timely resources to ensure decision-making in LAMs reflects the latest scientific understanding. Continual re-evaluation of SARS-CoV-2 policies is highly recommended as new scientific discoveries are published. 

Research questions

  • What implications does SARS-CoV-2 vaccination in the United States have for public health interventions and policies, especially related to indoor environments?
  • What differences have been found for SARS-CoV-2 variants (compared to the original strain) in the United States in terms of spread, transmissibility, surface attenuation, and effectiveness of public health interventions?
  • What effects do ventilation and ventilation-based interventions (e.g., heating, ventilation, and air conditioning systems (HVAC)) have on the spread of SARS-CoV-2 in indoor environments?


  • Ventilation: Researchers in Portugal sought to estimate the percentages of aerosol infection risk reduction of COVID-19 using a modeling approach. In schools, they found that completely opened windows lowered risk of infection by 64% when compared to closed windows. In mechanically ventilated spaces, risk of infection dropped significantly when air flow rates were doubled. Lastly, risk of infection was reduced by 72% when HEPA filters were used in schools. 
  • Variants: A study of the effectiveness of the Pfizer-BioNTech and Moderna vaccines in Qatar showed that although the vaccines were modestly effective in preventing infection with the Delta variant (55.5% effectiveness for either vaccine ≥14 days after the 2nd dose), the vaccines were highly effective in preventing severe, critical, or fatal disease (93.6%).
  • Vaccines: In a case-control study of 4,513 adults hospitalized with COVID-19 in 18 US states, patients vaccinated with an mRNA COVID-19 vaccine were significantly less likely to have died or undergone mechanical ventilation. ​

Notes for the reader

As you read this briefing, keep in mind a few key points:

  1. The research and information captured in the findings include both peer-reviewed and non-peer-reviewed studies. In the interest of publishing emerging research related to the COVID-19 pandemic as quickly as possible, publication has been expedited rather than waiting for time-intensive peer review.
  2. The review includes findings for industries, such as health care, that operate under considerably different constraints and risk factors than do libraries, archives, and museums (LAMs). However, it was important to consider a broad range of available research to determine what may be applicable to LAM operations and identify what research gaps exist. The research captured in the review does not represent recommendations or guidance for LAMs.
  3. Additional literature reviews and research briefings are available from REALM.
  4. A helpful resource for those interested in tracking the "known unknowns" about this virus is the DHS Master Question List for COVID-19 (caused by SARS-CoV-2).

Download the research briefing