Vaccination and disease transmission

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Quantity of SARS-CoV-2 RNA copies exhaled per minute during natural breathing over the course of COVID-19 infection

Vaccinated and unvaccinated individuals exhaled similar levels of SARS-CoV-2 RNA

We found that vaccinated and unvaccinated participants exhaled similar numbers of SARS-CoV-2 RNA copies

Viral RNA levels in vaccinated individuals on days 1 to 16

Ranged from 0 to 549 exhaled copies per minute

Viral RNA levels in unvaccinated individuals on days 1 to 16

0 to 876 exhaled copies per minute

P = 0.31

Levels of viral shedding on breath did not differ between these variant groups;

Early variants April 2020 and March 2021

0 to 876 RNA copies exhaled per minute

Delta (July 2021 to October 2021)

0 to 549 RNA copies exhaled per minute


0 to 264 RNA copies exhaled per minute Peak levels of viral shedding on breath were similar across variants

It is not yet known what an infectious dose of viral airborne particles is.


SARS-CoV-2 is spread through exhaled breath of infected individuals.

How much virus an individual is exhaling during normal breathing, over the course of their infection.

Previous studies focused on viral loads inside the respiratory tract, but not on breath.

COVID-19 patients used RTq-PCR Do not decrease significantly until day 8 from symptom-onset.

COVID-19-positive participants

Exhaled an average of 80 SARS-CoV-2 viral RNA copies per minute during the first 8 days of infection,

Significant variability between and within individuals, including spikes over 800 copies a minute in some patients.

After day 8, a steep drop to levels nearing the limit of detection, persisting for up to 20 days.

Levels of exhaled viral RNA increased with self-rated symptom-severity, though individual variation was high.

Levels of exhaled viral RNA did not differ

Across age, sex, time of day, vaccination status or viral variant.

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