How easily vaccinated people can spread COVID-19? – Community News
Covid-19

How easily vaccinated people can spread COVID-19?

Fears of breakthrough COVID-19 infections ruined the summer. In the early days of vaccine happiness, many Americans would have thought the injections were a ticket to normalcy — and at least for a while, that’s exactly what public health experts told us: Sure, it was still possible for vaccinated people to get COVID-19, but you don’t have to worry about spreading it to someone else. Interim guidelines shared by the CDC in March stated that these cases “probably pose little risk of transmission,” and a few weeks later, CDC director Rochelle Walensky said “vaccinated people do not carry the virus.”

And then came Delta. The hyper-contagious variant caused cases to skyrocket and led to ICUs once again being overcrowded with COVID patients. And it also caused a complete panic that our understanding of who could be spreading the virus was all wrong. In early August, the CDC released its findings on a massive cluster of COVID cases in Provincetown, Massachusetts, concluding that 74 percent of cases had occurred in vaccinated people. The supposed implication of that finding was even more ominous: Vaccinated people were just as likely to spread the virus as unvaccinated people. The CDC quickly went back to recommending that vaccinated people wear masks indoors, while news outlets had headlines such as “Vaccinated people with breakthrough infections can spread the delta variant, CDC says.” The worst-case scenario — that vaccinated people could live their lives just seeding tons of new coronavirus cases — suddenly seemed possible.

Three months later, thankfully, we didn’t see this doomsday come true — the fears expressed by the Provincetown report were largely exaggerated. But that does not mean that the vaccinated are also free. Breakthrough infections still occur and can lead to transmission. But we still don’t know how widespread that spread actually is.

Vaccinated people generally spread the virus less, as they are significantly less likely to get infected. In early September, the CDC found that six unvaccinated people tested COVID positive for every vaccinated person. But otherwise there are plenty of reasons to be optimistic. Some recent studies show that even once infected, the vaccinated people are less likely to spread the coronavirus than the unvaccinated. “We are back in this category of Yes it can happen but it seems to be a very rare eventRoss Kedl, a professor of immunology at the University of Colorado School of Medicine, told me.

He pointed me to two studies, neither of which have been peer-reviewed, to make his point. One shows that although transmission has occurred among those vaccinated in Provincetown, these cases represent what Kedl calls a “very limited” portion of the total number of infections that occurred as part of that outbreak. In the other study, researchers in the United Kingdom found that the Pfizer and AstraZeneca vaccines consistently reduced downstream transmission of breakthrough cases. Much of the original Delta concern was based on something called “viral load” — the amount of virus a person carries while infected. But the researchers concluded that viral load is just one of many factors associated with transmission reduction. In other words, even if vaccinated and unvaccinated people have the same viral load, it doesn’t necessarily mean they are equally likely to spread the virus.

One reason for this may be that vaccinated people carry fewer infectious virus particles, as recent (not yet peer-reviewed) research from the Netherlands has shown. While it’s commonly believed that virus particles carried by vaccinated and unvaccinated are the same, the basics of immunology actually predict differently, Kedl told me. Virus particles shed by a vaccinated person are thought to be covered in antibodies — some of which are produced in the nose and mouth and considered part of “mucosal” immunity — so “we can expect less downstream transmission,” he said.

Other researchers have come to similar conclusions. “The data is very clear that vaccinated individuals are less likely to spread the virus to others than unvaccinated individuals,” Christopher Byron Brooke, an assistant professor at the University of Illinois at Urbana-Champaign, told me in an email. A recent paper Brooke co-authored found that vaccinated people shed less virus, stop spreading viruses faster than unvaccinated people and shed fewer infectious particles, supporting the idea that they are less likely to transmit disease. A study from the Netherlands found a 63 percent reduction in household transmission among the vaccinated. That’s a testament to our vaccines: Homes are an “environment where the deck is heavily stacked for transmission as household members are in extremely close contact for long periods of time,” Brooke said. (However, another recent study did not find a statistically significant difference in household transmission between vaccinated and unvaccinated people.) Ultimately, Brooke said, you can certainly say that the transmission risk for vaccinated people is lower, “but I know not really how you define ‘low’.”

The new research has so far not affected the CDC, which remains cautious. An agency spokesperson told me in an email that the data that has come out since the Provincetown study makes clear that fully vaccinated people with breakthrough infection can spread the virus to other people, including the vaccinated. While the science is still emerging, the spokesperson said that “it appears that fully vaccinated people with breakthrough infection may be equally contagious at least shortly after infection and probably slightly less contagious to others than unvaccinated people who are infected. “

Other public health experts are also wary. “I think the jury is still out on how much vaccination can reduce the risk of transmission, but we do know that transmission does occur,” Lisa Maragakis, senior director of infection prevention at the Johns Hopkins Health System, told me. . “I wouldn’t say it’s low” [risk].” She hinted at data showing similar viral loads in vaccinated and unvaccinated people.

All the researchers I spoke to agreed on one thing: vaccination is still the best way to protect against infection and transmission. The vaccines may not be perfect, but they are by far the best tool we have in the fight against COVID-19 – to protect both yourself and others. In addition, vaccinated people can prevent the spread of the virus by avoiding situations where it is more likely to happen. When it comes to breakthrough infections, “behavior hasn’t been discussed enough,” said Syra Madad, an epidemiologist at New York City Health and Hospitals. The Provincetown event, which had packed indoor parties during Delta’s rise, wasn’t exactly conducive to breakout prevention. Precautions such as masking and ventilation are still important. For those reasons, Maragakis will “look at the data with concern” as the holiday season approaches: More indoor gatherings could lead to more breakthrough infections — and more spread.

Another joker is how long it’s been since we got our vaccine. As the UK newspaper showed, transmission protections started to wear off after about three months, although most data indicates that overall protections are still quite strong. For people under the age of 60, a breakthrough infection can mean you feel miserable for a week, but it doesn’t often lead to hospitalization. This age group isn’t likely to spread the virus as quickly — especially to other vaccinated people — because of their stronger immunity, Kedl told me. But the same cannot be said of vaccinated people aged 65 and over, who have weaker immune systems making them more vulnerable to serious disease and transmission – hence the need for booster shots. The “million dollar question” now, Maragakis said, is how often we will need boosters in the coming months and years.

We may not reach a consensus on how contagious breakthrough infections are, and that’s okay. Uncertainty is part of life with the coronavirus, even some 20 months after the pandemic. Until we know for sure, caution is the best way to protect those around you. That means “Isolate anyone who has an infection,” Maragakis said. “I’d be very reluctant to tell them they’re not at risk of giving it to others.” Unfortunately, while getting the vaccine will safely let you do many activities, it doesn’t give you carte blanche to pretend it’s 2019.

At best, getting a breakthrough infection one day will be like getting the flu. “Eventually everyone will become infected with this virus at some point, regardless of vaccination status, as the virus becomes endemic,” Brooke said. If enough people get the shot — and if the immunity continues — the consequences of vaccinated people potentially spreading the virus will ultimately be nothing to panic about.