Fauci: There’s evidence COVID-19 vaccines don’t just protect you — they may stop you from spreading the virus to others, too

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  • Dr. Fauci is touting some of the first evidence that vaccines can help stop the spread of COVID-19.
  • The hunch hinges on 2 new studies, which suggest vaccinated people don’t spread the coronavirus well, even if they do get sick.
  • Getting vaccinated, Fauci said, is “not only good for you,” it can protect others too.
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Dr. Anthony Fauci says there’s new evidence that a COVID-19 vaccine may not just protect the people who get it but also protect others whom they come in contact with.

“There have been some studies that are pointing into a very favourable direction,” Fauci, the director of the National Institute for Allergy and Infectious Diseases, said on Wednesday during a White House COVID-19 briefing.

While he said more conclusive research was still needed, the doctor pointed to two studies out this month.

Taken together, they are some of the earliest evidence we have that even if vaccinated people do get sick with COVID-19 — in what’s called a “breakthrough” infection — the chances that they would then transmit their illness onto others are far lower than if they had remained unvaccinated.

The No. 1 “looming question,” Fauci said, is: “Does vaccine prevent transmission?”

These two studies are early signs pointing toward a “yes.”

Not everyone who gets COVID-19 passes it on, whether they are vaccinated or not

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A health worker administers a dose of the Pfizer-BioNtech COVID-19 vaccine on January 23. Jack Guez/AFP via Getty Images

The first piece of evidence, a peer-reviewed study published in The Lancet earlier this month, suggests that people who are infected with COVID-19 but have lower viral loads in the back of their nose and throat are much less likely to infect others.

In the study, conducted in Spain during March and April, scientists measured how much virus 314 coronavirus patients had during their infections by swabbing way up inside their noses (nasopharynx) and measuring their viral loads.

Then they looked at which of those patients transmitted the coronavirus to someone else.

They found that the higher a patient’s viral load was, the more likely they were to pass their illness on to someone they came in contact with. Also, the higher the spreader’s viral load was, the faster the person they infected tended to get sick.

“In other words, higher viral load, good transmissibility, low viral load, very poor transmissibility,” Fauci said.

Until now, it wasn’t known whether viral load affected infectiousness, so there was some concern that even people with low levels of virus could spread their illnesses around well.

But it’s important to note that this study was performed nearly a year ago, when there wasn’t as much concern about fast-spreading variants, so it’s tough to interpret what it means for viral load and infectiousness now.

Vaccinated people seem to have less virus to spread around, even if they do get sick

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Dr. Anthony Fauci receives his first dose of a COVID-19 vaccine on December 22. Patrick Semansky-Pool/Getty Images

The second study, which came out last week and has not yet been peer-reviewed, suggested that people who were vaccinated in Israel had “significantly reduced” viral loads, when and if they got sick, starting at least 12 days after full vaccination.

Taken together, these two studies suggest that:

  • Vaccinated people tend to have lower viral loads.
  • Lower viral loads are linked to less viral spread.

It’s possible, then, that vaccinating large numbers of people could help to crush the coronavirus outbreak, by not only keeping vaccinated people healthy, alive, and out of the hospital but also preventing any of those vaccinated people who might get sick (even asymptomatically) from passing their sickness along to others.

“It is another example of the scientific data starting to point to the fact that vaccine is important, not only for the health of the individual, to protect them against infection and disease,” Fauci said, “but it also has very important implications from a public-health standpoint for interfering and diminishing the dynamics of the outbreak.”

More studies on viral loads in vaccinated people will need to be completed, and validated, from independent scientists in other countries around the world to see if this trend holds true globally. (Both Moderna and Pfizer already have such studies in the works, Fauci said.)

But in Israel, which has raced to the head of the global pack with nearly 30% of Israelis now fully vaccinated, there is positive evidence. Another new study from Israel’s largest healthcare provider this week suggests that among people who’ve been vaccinated with Pfizer’s messenger RNA shots, there’s been a 94% drop in symptomatic COVID-19 cases compared with their unvaccinated peers.

Getting vaccinated is “not only good for you and your family and your community,” Fauci said. “It will have a very important impact on the dynamics of the outbreak in our country.”