A growing body of evidence suggests that the Covid-19 vaccine may slow the spread of the coronavirus, said Dr. Anthony Fauci on Wednesday.
Whether vaccination can prevent transmission of the virus is “the imminent issue,” said Fauci, director of the National Institute of Allergy and Infectious Diseases, during a coronavirus response team briefing at the White House. “If a person is infected despite being vaccinated – we refer to it as a ‘breakthrough’ infection – does that person have the ability to pass it on to another person?”
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“Some studies point in a very favorable direction,” he said, adding that these studies will have to be supported by additional research.
Fauci highlighted two recent studies that looked at a person’s viral load – that is, the amount of virus they have in the body – and transmissibility.
A study from Spain, published on February 2 in The Lancet, found a direct correlation between viral load and transmissibility. The higher the viral load, the greater the transmissibility of the virus.
This is in line with what years of HIV research has shown: there is a direct link between the viral load in someone’s blood and the likelihood that the individual will transmit HIV to a sexual partner, said Fauci.
For SARS-CoV-2, the virus that causes Covid-19, the researchers are focused on how much virus is found in the nasopharynx, the upper part of the throat behind the nose, which is reached with a long, thin cotton swab.
The second study described by Fauci – an article that has not gone through peer review that was posted last week on the prepress server medRvix – looked at coronavirus infections in Israel, a country with very high vaccination rates.
That document found that individuals who became infected after receiving their first dose of the Pfizer-BioNTech vaccination had a “markedly decreased” viral load compared to unvaccinated people.
It is another example of “scientific data beginning to point to the fact that [the vaccine] … It has very important implications from the point of view of public health to interfere and reduce the dynamics of the outbreak, ”said Fauci.
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Dr. John Anthony Vanchiere, head of pediatric infectious diseases at Ochsner LSU Health Shreveport in Louisiana, said the two studies “go very well together”.
“We know that it is the case of influenza and other respiratory viruses that higher viral loads are associated with increased transmission,” he said. “The fact that the vaccine reduces viral load, even after receiving the first dose, is very important data to have. “
Both Pfizer-BioNTech and Moderna are currently studying how vaccination affects transmissibility, said Fauci.
“The final message,” he said, is “when it is your turn to be vaccinated, be vaccinated. It is not only good for you, your family and the community, but it will have a very important impact on the dynamics of the outbreak in our country.”
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Akshay Syal contributed.