The researchers, including those from U.S. Centers for Disease Control and Prevention (CDC), noted that aircraft can hold large number of people in close proximity for long periods, which are conditions that can increase the risk for transmitting infectious diseases.
Based on laboratory modelling of exposure to SARS-CoV-2 on single-aisle and twin-aisle aircraft, exposures in scenarios in which the middle seat was vacant were reduced by 23 per cent to 57 per cent, compared with full aircraft occupancy, the researchers noted.
Lately, airlines have abandoned the pandemic practice of blocking seats to maintain physical distancing between the travellers
"Physical distancing of airplane passengers, including through policies such as middle seat vacancy, could provide additional reductions in risk for exposure to SARS-CoV-2 on aircraft," the researchers concluded.
The team of researchers from CDC and Kansas State University (KSU) in the US used a bacteriophage – a virus that infects bacteria -- as a surrogate for airborne SARS-CoV-2.
They modelled the relationship between SARS-CoV-2 exposure and aircraft seating proximity, including full occupancy and vacant middle seat occupancy scenarios.
"Compared with exposures in full occupancy scenarios, relative exposure in vacant middle seat scenarios was reduced by 23 per cent to 57 per cent depending upon the modelling approach,” the researchers said.
A 23 per cent exposure reduction was observed for a single passenger who was in the same row and two seats away from the SARS-COV-2 source, rather than in an adjacent middle seat, they said.
When quantifying exposure reduction to a full 120-passenger cabin rather than to a single person, the study predicted exposure reductions ranging from 35 per cent to 39.4 per cent.
A 57 per cent exposure reduction was observed under the vacant middle seat condition in a scenario involving a three-row section that contained a mix of SARS-CoV-2 sources and other passengers, according to the researchers.
Based on this laboratory model, a vacant middle seat reduces risk for exposure to SARS-CoV-2 from nearby passengers, they said.
Last year, a Harvard study, paid for in part by the US airline industry, claimed that the ventilation on planes, together with other measures, reduces the possibility of greater exposure to COVID-19.
The researchers acknowledge some limitations in the CDC study, including the fact that data were collected under higher relative humidity conditions in the laboratory than would be present during flight.
Droplet evaporation into aerosol is more rapid under lower relative humidity, they said.
Because aerosols travel farther than droplets, the current study might underpredict the aerosol spread in an actual cabin environment, according to the researchers