Is it safe to fly now? Upstream PCR testing could be the answer


A study conducted earlier this year shows that there may be a way to reduce the number of Covid infections on board commercial planes to virtually zero.

The results of the study were published in a peer reviewed article published September 1 in the medical journal Mayo Clinic Proceedings. The article – a joint effort of the Mayo Clinic, Georgia Department of Public Health and Delta Air Lines – showed that a polymerase chain reaction (PCR) test performed within 72 hours of the flight reduced the rate of travelers infected on board at 0.05%. That’s five people for 10,000 passengers.

At the time of the study, the infection rate in the United States was 1.1%, or about 1 in 100 people.

“A damn low number”

The results analyzed data from Delta’s pre-testing program which ran from December 2020 to May 2021.

Here’s how Delta’s testing program worked: Passengers on select flights from New York and Atlanta could travel to Italy, without having to quarantine themselves upon arrival, if they tested negative for Covid-19. via PCR test within 72 hours before flight, antigen test before departure and rapid antigen test on landing.

Data from Delta’s upstream testing program provides new insight into test feasibility, test accuracy and passenger infection rates on commercial flights.

Mario Tama | Getty Images News | Getty Images

Of the 9,853 people who tested negative via the PCR test, four tested positive at the airport via rapid antigen testing. The diagnoses were confirmed via a rapid molecular test, and these people were not allowed to fly.

Among the passengers who flew to Italy, one tested positive on landing.

This translates to one case detection per 1,970 travelers “during a period of high prevalence of active infection in the United States,” according to the article.

“That’s a pretty darn low number,” said lead author Dr. Aaron J. Tande of the article and infectious disease specialist at the Mayo Clinic in Rochester, Minnesota.

The study suggests that a PCR test within three days of the flight makes subsequent testing at the airport largely unnecessary, especially when combined with onboard masking requirements and increasing vaccination rates among travelers .

‘Limitations of the study

The newspaper article mentions several “limitations” that may have affected the study results, including the role of preflight testing on traveler behavior. Participants suspected of being infected with Covid may have chosen not to travel. Others may have been more diligent in wearing masks and self-isolating knowing they had to test negative in order to fly, Tande said.

“I can’t say that’s what made the number of positive tests so low – or was it really that the 72-hour test was so good,” he told CNBC. “But… the end result is it’s a safer flight for people, and that’s what we want.”

If you repeated the study now … I think you will see a significant decrease in the infection rate on board.

Dr Aaron J. Tande

Mayo Clinic

Tande said the results are based on the strains of Covid-19 that were circulating in the United States during the first half of 2021, not the more contagious delta variant that currently dominates.

“I don’t think you can say that if you repeated the study now – with a different community infection rate and a different virus – you would get the exact same result,” he told CNBC. “I think you would see a significant decrease in the infection rate on board.”

Safer but less feasible options

The pilot program considered five testing strategies, two of which may have detected even more infected leaflets.

For example, a single rapid molecular test at the airport may have found more infections because it minimizes the time between testing and flight, and thus could detect infections that occur during that time. Adding a 72-hour PCR preflight test would likely find even more, according to the study.

While airports weren’t designed for large-scale medical testing, many set up makeshift facilities last year, like Rome’s Fiumicino International Airport pictured here.

Alessia Pierdomenico | Bloomberg | Getty Images

However, an upstream PCR test is the “best approach” because it is more feasible, Tande said. PCR tests are widely available, more “sensitive” – ​​which means they detect positive cases better – and they remove the logistics of testing at airports, he said. Advanced testing also gives infected travelers time to rearrange their plans, rather than surprising them right before their flights depart.

Test or vaccinated flights?

Upstream PCR testing can make the flight safer, but most passengers now fly without. And the airlines are discreet about their obligation going forward.

However, testing could become a de facto rule on international flights if arriving countries require it for passenger entry. A spokesperson for Delta Air Lines declined to say whether it would require testing for its passengers, but said “each country’s government is responsible for setting its own requirements.”

Tande said he would feel safer taking a flight that would require passengers to take PCR tests up front. Still, if given a choice, he said he preferred a vaccination-only flight more.

“I would definitely go for the vaccinated flight – and (I) would mask myself,” he said.

Qantas CEO Alan Joyce said last week that passengers will need to be vaccinated on its international flights, according to news.com.au. U.S. officials are currently debating whether to require vaccinations to fly both domestically and internationally, as reported this week. The Washington Post.

“Unfortunately, because of vaccine attitudes, Covid is going to be with us for a long time,” Tande said. “With the masking and continuous testing before we fly… we can improve safety so that we can continue to function sort of like a normal society.”

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