Nurses care for a Covid-19 patient inside the intensive care unit at Adventist Health in Sonora, California on August 27, 2021 ( AFP / Nic Coury)

Study did not say vaccinated Covid-19 patients carry higher viral load

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Online articles and social media posts claim a University of Oxford study found that vaccinated Covid-19 patients carry 251 times the viral load of those who have not received the shots. But the study's authors said the claim is a misrepresentation of their findings, as did a public health expert.

"A preprint paper by the prestigious Oxford University Clinical Research Group, published Aug. 10 in The Lancet, found vaccinated individuals carry 251 times the load of Covid-19 viruses in their nostrils compared to the unvaccinated," says an August 23, 2021 article published by Robert F Kennedy Jr’s anti-vaccine advocacy organization Children’s Health Defense.

Screenshot of an online article taken on September 8, 2021

The article was written by Peter McCullough, a doctor who made a series of inaccurate claims about Covid-19 vaccines in testimony to the Senate of the US state of Texas.

The viral load claim also appeared on Instagram here and here, and in another online article here.

But the study authors, who analyzed breakthrough infections among health care workers at a hospital in Vietnam, issued a statement addressing the claim, calling it "false" and a "misrepresentation of the data."

They compared viral loads from patients infected with the original SARS-CoV-2 strain with those from fully vaccinated health care workers infected with the highly contagious Delta variant.

Their preliminary results showed that "viral loads of breakthrough Delta variant infection cases were 251 times higher than those of cases infected with old strains detected between March-April 2020."

The authors said in the statement that "the differences in viral load were driven by the ability of the Delta variant to cause higher viral loads; they had nothing to do with the vaccination status of the infected individual.

"Thus the claim that vaccinated individuals carry 251 times the loads of SARS-CoV-2 in their respiratory tract compared to the unvaccinated people is a misrepresentation of the data," they said.

Public health researcher Devon Greyson, a professor at the University of British Columbia's School of Population and Public Health, called the claim "an egregious misinterpretation of the findings."

"What this study actually does is compare Delta infections to earlier variants... but it says little about vaccinated vs unvaccinated people," Greyson said.

Additionally, the medical journal The Lancet, which published the study, included a notice that it was preliminary.

"These preprints are early stage research papers that have not been peer-reviewed," the disclaimer says.

"The findings should not be used for clinical or public health decision making and should not be presented to a lay audience without highlighting that they are preliminary and have not been peer-reviewed."

AFP has fact-checked other inaccurate claims about Covid-19 here.

September 9, 2021 This article was updated to remove an extraneous word.