SARS-CoV-2 Human Challenge Study Belies Presymptomatic Transmission

Introduction

On April 15, 2020, a study was published in Nature Medicine that was widely cited to support the claim that people without symptoms accounted for nearly half of community transmission of SARS‑CoV‑2, the coronavirus that causes COVID‑19. That study, conducted by Xi He et al. and titled “Temporal dynamics in viral shedding and transmissibility of COVID‑19”, estimated that 44 percent of transmission occurred before the onset of symptoms, or the “presymptomatic” stage of infection.

It was that same team’s research that the New York Times had cited, for example, to support the claim that 20 to 40 percent of transmission occurs before symptoms, as reported on March 31, 2020, under the headline “Infected but Feeling Fine: The Unwitting Coronavirus Spreaders”. It was based upon this fear that the US Centers for Disease Control and Prevention (CDC) subsequently issued its recommendation for universal mask use by members of the public in the community setting.

It also was based upon this fear that transmission was largely driven by symptomless people that the New York Times published an opinion piece on April 26, 2020, advocating “widespread testing of people with no known symptoms”.

On June 9, 2020, after a World Health Organization (WHO) official publicly acknowledged that studies had shown asymptomatic transmission to be “very rare”, the New York Times published an article criticizing the statement and falsely reporting that, after an outcry from the scientific community, the WHO had “walked back” the statement.

The truth was that the media had simply misreported the WHO official’s statement as meaning that it was very rare for people without symptoms to spread the virus, when in fact the WHO official had distinguished between transmission from “asymptomatic” individuals, meaning those who never developed any symptoms, and “presymptomatic” individuals, meaning those who would go on to develop symptoms. Far from walking back the statement, the WHO had simply clarified the distinction once again for incompetent reporters.

In the context of its false claim that the WHO had “walked back” the truthful statement, the Times cited the “widely cited” study in Nature Medicine as finding that “people are most infectious up to two days before the onset of symptoms”—as though this finding belied the WHO official’s statement when in fact it did not (since it was a study estimating presymptomatic and not asymptomatic transmission).

The same day, the Washington Post ran an article acknowledging that “it remains an open question” whether truly asymptomatic individuals “are a large force driving transmission”, but the Post cited the “influential” Nature Medicine study as support for the claim that a very high proportion of people “can be very infectious roughly two days before symptoms appear.”

When the CDC published its “best estimate” in July 2020 that 50 percent of community transmission occurred “prior to symptom onset”, it cited “the upper 95% confidence interval” from the Nature Medicine study as its “upper bound”.

Of course, as advocated in the pages of the New York Times, mass testing of individuals regardless of any clinical presentations of disease is precisely what occurred. The result was that “up to 90 percent of people testing positive” with PCR tests were unlikely to be contagious, as the Times finally admitted in August 2020, despite it being well understood from the start within the scientific community that running these tests at high cycle threshold values resulted in a high rate of false positive tests, with people testing positive for the presence of non-viable viral RNA or “background noise”, rather than positive tests indicating the presence of infectious virus.

In fact, it was for precisely this reason that the World Health Organization (WHO) had issued guidance to test only those presenting with symptoms or who had had a clear exposure to someone with COVID‑19.

This misuse of PCR tests as a sole basis for diagnosis resulted in systematic scientific fraud in the counting of “COVID‑19 cases”—all based upon the idea that “silent spreaders” were major drivers of community transmission of the coronavirus.

On February 1, 2022, a preprint study by Ben Killingley et al. was published at Research Square that overturned the primary basis for the conclusion that 44 percent of transmission occurred during the presymptomatic phase of infection. Uniquely, it was a SARS‑CoV‑2 human challenge study that enabled researchers to overcome certain limitations inherent to other studies relevant for estimating how contagious people are before they develop symptoms.

The study’s authors include Neil Ferguson from Imperial College London, whose infamously flawed modeling study in March 2020, which advocated continued lockdown measures until a vaccine could be rapidly developed and mass administered, served as the basis for policymakers’ decision to inflict the devastating authoritarian lockdown measures on the population.

The human challenge study subsequently underwent peer review and was published in Nature Medicine on March 31, 2022, with the title “Safety, tolerability and viral kinetics during SARS‑CoV‑2 human challenge in young adults”.

Providing a useful illustration of how researchers’ conclusions are frequently contradicted by their own findings, the authors asserted that their findings are “consistent with modeling data indicating that up to 44% of transmissions occur before symptoms are noted”—a reference to the earlier study in the same journal by Xi He et al.

In fact, the findings of the human challenge study directly contradict the basis for that 44 percent estimate, showing that, rather than viral loads in the upper respiratory tract peaking about two days prior to symptom onset, viral loads peak at about the same time as symptoms.