NEW YORK - As more people pack their bags to travel, a new study found that the risk of exposure to COVID-19 while on a Delta flight decreased significantly due the airline’s pre-flight testing for the virus.
According to the peer-reviewed study published in "Mayo Clinic Proceedings," the risk of infection after all passengers tested negative 72 hours in advance of the flight was less than 0.1 percent.
Researchers examined data on Delta’s COVID-19-tested flight corridors between New York’s JFK, Atlanta and Italy’s Fiumicino International Airport.
The 15-page study showed a single COVID-19 molecular test performed within 72 hours of departure could decrease the rate of people actively infected onboard a commercial aircraft to a level that is significantly below active community infection rates.
Among 9,853 passengers with a negative SARS-CoV-2 PCR performed within 72 hours of departure from December 2020 through May 2021, five (0.05%) passengers with active SARS-CoV-2 infection were identified with rapid antigen tests and confirmed with rapid molecular test performed before and after an international flight from the United States to Italy.
This translates to a case detection rate of one per 1970 travelers during a time of high prevalence of active infection in the United States, according to the study.
"These data suggest that even at this higher level of active community infection, a single molecular test performed within 72 hours of departure can decrease the rate of active infection on board a commercial aircraft to a level that is several orders of magnitude below active community infection rates," the study authors wrote.
While there have been several case reports and simulation models of SARS-CoV-2 transmission associated with air travel, there are still limited data to guide testing strategy to minimize the risk of exposure onboard commercial aircraft, the study noted.
In a separate study released in June, Qatar implemented a pilot program between Feb. 18 and April 26 to ease travel restrictions by waiving the quarantine requirement for vaccinated residents who received their second vaccine dose at least 14 days before arrival. The program still required a PCR test to be performed on each passenger on arrival at Hamad International Airport.
Researchers in the study found vaccination and prior infection were associated with reduced risk for SARS-CoV-2 PCR test positivity in residents of Qatar returning on international flights. Nevertheless, both vaccine immunity and natural immunity were imperfect, with breakthrough infections recorded, which highlighted the need to maintain PCR testing for arriving travelers.
Earlier this month, United Airlines announced it would require employees in the U.S. to be vaccinated against COVID-19 by late October. Frontier announced a similar policy this month, requiring employees to be vaccinated or provide "regular" proof of a negative COVID-19 test.
The two major airlines join a growing number of companies that are responding to a surge in COVID-19 cases by requiring the shots.
"When you couple the extremely low infection rate on board a COVID-19-tested flight with the layers of protection on board including mandatory masking and hospital-grade air filtration, the risk of transmission is less than one in one million between the United States and the United Kingdom, for example," Dr. Henry Ting, Delta’s chief health officer, said in a statement. "These numbers will improve further as vaccination rates increase and new cases decrease worldwide."
This story was reported from Los Angeles.