The risk of contracting coronavirus increases the longer you are exposed to it, even for people who have been vaccinated

Color scanning electron micrograph of the SARS-CoV-2 Omicron variant.

Viral particle (artificially colored) of the SARS-CoV-2 Omicron variant.Credit: Steve Gschmeisner/Science Image Library

A study revealed that prolonged exposure in close proximity to a person infected with Covid-19 puts people at a high risk of contracting the disease, even if they have obtained the disease and vaccinations against it.1 Offers.

The study was published this month in Nature CommunicationsIt reveals that the more a person is exposed to SARS-CoV-2, the more susceptible they become, regardless of their vaccination status. This relationship has long been questionable, but this study is the first of its kind to document it.

The results point to the importance of wearing a mask, improving ventilation and other measures that reduce exposure to the virus, says Akiko Iwasaki, an immunobiologist at Yale University in New Haven, Connecticut, who was not part of the study.

She says the result “makes intuitive sense.” “But there is now evidence that these (measures) may be important for helping vaccine-mediated immunity work in your favor.”

Close contacts

Scientists have speculated since the beginning of the pandemic that the likelihood of contracting SARS-CoV-2 is related to the amount of virus a person is exposed to. But verifying this relationship has been difficult due to challenges in determining the amount of time people spend in close contact with others, and in tracing infection after such contact.

To obtain such data, the study authors turned to 13 correctional facilities in Connecticut that regularly perform SARS-CoV-2 tests on asymptomatic residents. The researchers assigned a “close exposure” status to anyone who shared a cell with an infected person, and a “moderate” exposure status to those who shared a mass of cells but not a cell with an infected resident. Those who lived in cell blocks separate from anyone known to be infected were classified as having no documented exposure.

“The design is very powerful,” says Jose Luis Jimenez, an aerosol scientist at the University of Colorado at Boulder. ‚ÄúThis is the only situation where you can directly control how people move and where they are. This eliminates one of the things that makes this type of study difficult.

The authors’ analysis of more than 10,000 residents and hundreds of SARS-CoV-2 infections found that vaccination, prior infection, or both, protected populations with no documented exposure to the virus, or only moderate exposure. But neither vaccination, nor previous infection, nor both provide significant protection for those who have been exposed closely, says Margaret Lind, an epidemiologist at Yale University in New Haven, Connecticut, and a co-author of the study.

Jimenez says the new study is consistent with his work2 In “superspreading” events, which showed that the duration of exposure to someone with COVID-19 was one of a large number of factors that could predict the chances of contracting SARS-CoV-2. The spread of new viral variants, in addition to weakened immunity from vaccinations or previous infections, also plays a role in understanding a person’s risk of infection.

But many of these factors are beyond the control of people weighing infection risk, says Lind, while wearing a mask and avoiding crowded places is “the really modifiable thing, and it gives me some relief.” A logical next step from our findings is that reducing your exposure through these mitigation policies would be beneficial.

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