Impact of COVID-19 vaccination on transmission risk of breakthrough infections: Lessons from adapted N95 mask...

This study used an adapted N95 mask sampling to understand the effect of COVID-19 vaccination in the context of circulating variants on infected individuals to emit the virus into the air, a key risk factor of transmission. Mask, swab, and blood samples were collected from 92 COVID-19 patients vaccinated (Covishield/COVAXIN-partial/fully) or unvaccinated between July and September 2021 during the Delta-dominated period in Mumbai. Mask/swab samples were analyzed by reverse transcription polymerase chain reaction for viral RNA. Blood was evaluated for SARS-CoV-2 anti-spike and nucleocapsid antibody responses. At <48 h of diagnosis, 93% of the patients emitted detectable viral RNA, with 40% emitting >1000 copies in 30 min (high emitters). About 8% continued to be high emitters even after 8 days of symptom onset. No significant difference was observed in emission patterns between partial, full, and unvaccinated patients. However, when vaccinated patients were stratified based on spike protein neutralization and nucleocapsid immunoglobulin G (IgG), the group with moderate/high neutralization showed a significantly lower proportion of high emitters and viral RNA copies than the group with no/low neutralization, which further reduced in the group having antinucleocapsid IgG. In conclusion, mask sampling showed that Delta infections were associated with greater virus emission in patients, which was significantly reduced only in vaccinated patients with moderate/high SARS-CoV-2 neutralization, especially with evidence of past infection. The study demonstrated that mask sampling could be useful for understanding the transmission risk of emerging variants, screening vaccine/booster candidates, and guiding control interventions.