When researcher Monica Gandhi began digging deeper into outbreaks of the novel coronavirus, she was struck by the extraordinarily high number of infected people who had no symptoms.

A Tyson Foods poultry plant in Springdale, Ark., had 481 infections, and 95 percent were asymptomatic.

Prisons in Arkansas, North Carolina, Ohio and Virginia counted 3,277 infected people, but 96 percent were asymptomatic.

Efforts to understand the diversity in the illness are finally beginning to yield results, raising hope the knowledge will help accelerate development of vaccines and therapies — or possibly even create new pathways toward herd immunity in which enough of the population develops a mild version of the virus that they block further spread and the pandemic ends.

“A high rate of asymptomatic infection is a good thing,” said Gandhi, an infectious-disease specialist at the University of California at San Francisco.

31, 2019, public health officials deemed it a “novel” virus because it was the first time it had been seen in humans who presumably had no immunity from it whatsoever.

Hans-Gustaf Ljunggren, a researcher at Sweden’s Karolinska Institute, and others have suggested that public immunity to the coronavirus could be significantly higher than what has been suggested by serology studies.

But if others had partial protection from T cells, that would raise a community’s immunity level much higher.

Asked and answered: What readers want to know about coronavirus.

Some experts have gone so far as to speculate whether some surprising recent trends in the epidemiology of the coronavirus — the drop in infection rates in Sweden where there have been no widespread lockdowns or mask requirements, or the high rates of infection in Mumbai’s poor areas but little serious disease — might be due to preexisting immunity.

But scientists believe another part of our immune system — T cells, a type of white blood cell that orchestrates the entire immune system — could be even more important in fighting against the coronavirus.

While work on T cells and the coronavirus is only getting started — testing T cells is much more laborious than antibody testing — previous research has shown that, in general, T cells tend to last years longer.

In a study from the Netherlands, T cells reacted to the virus in 20 percent of the samples.

Interestingly, the researchers noted in their paper, the strongest reaction they saw was against the spike proteins that the virus uses to gain access to cells — suggesting that fewer viral copies get past these defenses.

“But if some people have some level of preexisting immunity, that may suggest it’s not a switch but more continuous.”.

Teaming up with data experts from nference, a company that manages their clinical data, he and other scientists looked at records from 137,037 patients treated at the health system to look for relationships between vaccinations and coronavirus infection.

The results were intriguing: Seven types of vaccines given one, two or five years in the past were associated with having a lower rate of infection with the new coronavirus.

Two vaccines in particular seemed to show stronger links: People who got a pneumonia vaccine in the recent past appeared to have a 28 percent reduction in coronavirus risk.

In the Diamond Princess, where masks weren’t used and the virus was likely to have roamed free, 47 percent of those tested were asymptomatic.

Similarly high rates of asymptomatic infection were documented at a pediatric dialysis unit in Indiana, a seafood plant in Oregon and a hair salon in Missouri, all of which used masks?

While we don’t know what that level might be for the coronavirus (it would be unethical to expose humans in this way), previous work on other nonlethal viruses showed that people tend to get less sick with lower doses and more sick with higher doses?

In an article published this month in the Journal of General Internal Medicine, Gandhi noted that in some outbreaks early in the pandemic in which most people did not wear masks, 15 percent of the infected were asymptomatic.

But later on, when people began wearing masks, the rate of asymptomatic people was 40 to 45 percent.

Gandhi makes the controversial argument that while we’ve mostly talked about asymptomatic infections as terrifying due to how people can spread the virus unwittingly, it could end up being a good thing

“It is an intriguing hypothesis that asymptomatic infection triggering immunity may lead us to get more population-level immunity,” Gandhi said

‘Superspreading’ events, triggered by people who may not even know they are infected, propel coronavirus pandemic

Asked and answered: What readers want to know about coronavirus