A meta-analysis of 54 different studies has raised new questions about the prevalence of COVID-19 spread from asymptomatic carriers within households.
The new analysis, led by researchers from the Department of Biostatistics at the University of Florida, aggregates the findings of 54 studies with 77,758 participants on the spread of COVID-19 within households. The analysis concluded that the estimated secondary attack rate for symptomatic cases within households was 18%, while the estimated secondary attack rate in cases without symptoms was only 0.7%.
The secondary attack rate is defined as the portion of contacts an infected person has that go on to test positive for the same virus later. While the numbers from the University of Florida analysis may suggest that asymptomatic spread is quite rare, the results aren’t necessarily conclusive. (RELATED: Novavax COVID-19 Vaccine Proceeds To The Final Stage Of Testing)
Dr. William Schaffner, a professor and infectious disease expert at the Vanderbilt University Medical Center, told the Daily Caller there are some key methodological issues with the analysis. “Their review indicates that much more rigorous studies need to be done,” he said in a phone interview Monday.
Schaffner said there was a “great deal of variability among the studies,” pointing out the range of different sample sizes, methodologies and results. Possibly the biggest flaw was that many of the studies of asymptomatic spread only looked for symptoms to arise in contacts, and didn’t actually test all close contacts of the asymptomatic carriers. This means the studies using that methodology could have easily missed asymptomatic-to-asymptomatic transfers.
He also pointed out that the analysis, published Dec. 14, would not have been able to account for how new strains of the virus spread. “These new strains, particularly from the U.K. seem to be much more contagious… these [researchers] didn’t know about that.” (RELATED: House Passes Bill To Increase COVID-19 Relief Checks From $600 To $2,000)
The analysis states that 16 of the 54 studies examined were at “high risk of bias.” Nearly two-thirds of the studies had an average of fewer than one test per contact. In other words, not every contact of the infected individual was tested. 31 of the studies were deemed to have small sample sizes by the researchers.
This meta-analysis of 54 studies shows that symptomatic cases of #COVID19 spread 18% of the time whereas asymptomatic cases spread 0.7% of the time. Not impossible, but asymptomatic spread is just very inefficient https://t.co/gTz3NdKgnW via @JAMANetworkOpen part of @JAMANetwork
— Dr. Mark Slifka (@MarkSlifka) December 29, 2020
Previous research has indicated that asymptomatic spread is much more prevalent. The CDC has published findings that asymptomatic children can spread the virus, and another study estimated that up to 44% of COVID-19 cases are spread by pre-symptomatic individuals.
Still, the theory that asymptomatic spread is very rare has some support as well. In addition to the University of Florida analysis, a massive study out of Wuhan, China, found no evidence of asymptomatic spread. In June, the World Health Organization’s Dr. Maria Van Kerkhove described instances of asymptomatic carriers spreading the virus as “very rare.” (RELATED: REPORT: Wuhan Likely Had 10 Times More COVID-19 Cases Than China Reported)
Public uncertainty and mistrust of health officials and scientific research has been a major impediment to pandemic response. A recent poll found that two-thirds of Americans had at least some level concern about getting a COVID-19 vaccine. Dr. Anthony Fauci also recently admitted he had been changing his public statements to hide his real feelings about the virus because the public “wasn’t ready” to hear the truth.