SARS-CoV-2 breakthrough infections in vaccinated individuals and in those who had a prior infection have been observed globally, but the transmission potential of these infections is unknown. The RT-qPCR cycle threshold (Ct) value is inversely correlated with viral load and culturable virus. Here, we investigate differences in RT-qPCR Ct values across Qatar’s national cohorts of primary infections, reinfections, BNT162b2 (Pfizer-BioNTech) breakthrough infections, and mRNA-1273 (Moderna) breakthrough infections. Our matched-cohort analyses of the randomly diagnosed infections show higher mean Ct value in all cohorts of breakthrough infections compared to the cohort of primary infections in unvaccinated individuals. The Ct value is 1.3 (95% CI: 0.9–1.8) cycles higher for BNT162b2 breakthrough infections, 3.2 (95% CI: 1.9–4.5) cycles higher for mRNA-1273 breakthrough infections, and 4.0 (95% CI: 3.5–4.5) cycles higher for reinfections in unvaccinated individuals. Since Ct value correlates inversely with SARS-CoV-2 infectiousness, these differences imply that vaccine breakthrough infections and reinfections are less infectious than primary infections in unvaccinated individuals. Public health benefits of vaccination may have been underestimated, as COVID-19 vaccines not only protect against acquisition of infection, but also appear to protect against transmission of infection. SARS-CoV-2 breakthrough infections in vaccinated individuals and reinfections in those with prior infection are a public health concern. Here, the authors show that viral loads of vaccine breakthrough infections and reinfections are generally lower than primary infections of unvaccinated individuals, potentially indicating lower infectiousness.
【저자키워드】 viral infection, Epidemiology, 【초록키워드】 public health, SARS-CoV-2, COVID-19 vaccine, vaccination, mRNA-1273, Infection, Transmission, virus, BNT162b2, RT-qPCR, Reinfection, Cohort, Health, infections, Viral load, cycle threshold, transmission potential, breakthrough infections, Breakthrough infection, Pfizer-BioNTech, Moderna, Primary infection, Analysis, National, vaccinated individual, acquisition, Public, benefit, vaccine breakthrough infection, Randomly, PROTECT, diagnosed, less, correlated, individuals, 【제목키워드】 SARS-CoV-2 vaccine, breakthrough infections, Primary infection, relative,