In a blow to the COVID-19 “silent spreader” narrative that has been used to push for universal masking, including controversially among schoolchildren, a recent study published in The Lancet suggests that people who are non-symptomatic rarely have the ability to infect others.
Silent transmission is the idea that those who are infected with COVID-19 but show no symptoms can still spread the virus to other people.
While all relevant studies show that presymptomatic and asymptomatic “silent spreaders” account for some proportion of infections in other people, the degree of silent transmission is less clear.
A number of early studies—in some cases affected by limitations that may have led to their proportion of presymptomatic transmission to be “artifactually inflated”—suggested that silent transmission accounted for around half of secondary infections, or even more.
The early studies led public health authorities to argue that everyone should wear a mask at all times when out in public or crowded places. This, in turn, helped drive draconian universal masking policies, including in schools, in a bid to reduce the spread of COVID-19.
For instance, Dr. Anthony Fauci, former director of the National Institute of Allergy and Infectious Diseases (NIAID), initially discouraged universal mask-wearing early in the pandemic but later did a U-turn.
Initially, “we didn’t realize the extent of asymptotic spread,” Dr. Fauci said in July 2020, adding that later, “we fully realized that there are a lot of people who are asymptomatic who are spreading infection.”
“So it became clear that we absolutely should be wearing masks consistently,” Dr. Fauci said at the time.
But new research calls into question the significance of the threat of silent transmission, which comes as COVID-19 cases are on the rise in America, driving what some are calling a renewed pandemic “hysteria” and calls for a fresh round of restrictions, including mask mandates.
‘Very Few Emissions’ Before Symptom Onset
The new study, published in the August issue of The Lancet’s Microbe journal, shows that people who are sick with COVID-19 but don’t show any symptoms have a limited ability to spread the virus to other people.
Participants in the British study, which was carried out by researchers at Imperial College London, were unvaccinated healthy adults aged 18-30 who were intentionally infected with COVID-19.
The subjects were monitored under controlled circumstances while self-reporting symptoms three times per day, and researchers collected nose and throat swabs from them daily, checking for the presence of the virus.
The researchers also tested the inside of masks worn by the participants, checked their hands, and examined the air and surfaces of rooms that the subjects were kept in for a minimum of 14 days.
Ultimately, the researchers found that less than 10 percent of the viral emissions from infected participants took place before the first symptoms emerged.
“Very few emissions occurred before the first reported symptom (7%) and hardly any before the first positive lateral flow antigen test (2%),” the authors of the study wrote.
The new study—which takes the form of a rigorous, controlled “challenge study” rather than the earlier modeling studies that relied on subjective inputs and assumptions of researchers—contradicts earlier research that set the tone for much of the prevailing narrative. That early research appears to have inflated the perceived threat of presymptomatic spread.
The latest study, suggesting that silent transmission is far less significant, comes amid a growing drumbeat of alarm as COVID-19 cases, hospitalizations, and deaths are on the rise—along with calls in some circles for renewed restrictions.
By contrast, many are calling for cool heads to prevail—or are urging civil disobedience if lockdowns or other mandates are reimposed.
Some early studies, such as one published in August 2020 called “Temporal Dynamics In Viral Shedding and Transmissibility of COVID-19,” suggested that people who were presymptomatic or asymptomatic accounted for a large proportion of secondary infections.
This particular study estimated that 44 percent of secondary cases were infected during the presymptomatic stage, while concluding that “disease control measures should be adjusted to account for probably substantial presymptomatic transmission.”
The authors of the study admitted that it had several limitations, however, including potential “recall bias” that may have tended towards a delay in recognizing first symptoms.
“The incubation period would have been overestimated, and thus the proportion of presymptomatic transmission artifactually inflated,” meaning that the study may have exaggerated the proportion of people who spread the virus before showing symptoms, they said.
Another study from July 2020 called “The Implications of Silent Transmission for the Control of COVID-19 Outbreaks” went even further, suggesting that people were most infectious during the presymptomatic phase and concluding that silent transmission was the “primary driver of COVID-19 outbreaks and underscore the need for mitigation strategies, such as contact tracing, that detect and isolate infectious individuals prior to the onset of symptoms.”
That study relied on a range of assumptions and models, with different presymptomatic, asymptomatic, and symptomatic transmission rates calculated based on a complex mathematical model from another study.
Findings from earlier studies like the ones cited above led public health officials to argue that silent spreaders were a big factor in COVID-19 transmission and so to recommend that everyone should mask up.