22 diciembre, 2021

Transmission Risk in SARS-CoV-2–Infected, Fully Vaccinated Individuals: Real-World Data

Those who develop COVID-19 despite being fully vaccinated are considerably less infectious for contact persons, who in turn are protected from infection if vaccinated.

It has become evident that some individuals may develop COVID-19 despite full vaccination, especially if they are older or immunocompromised and if longer intervals have elapsed since the second dose. Even though COVID-19 is then generally mild (or asymptomatic), transmission of the virus may occur — and the infectiousness of dually vaccinated individuals with COVID-19 remains unclear. Now, a population-based study in Cologne, Germany, provides some answers. Between December 27, 2020 (the date of the first vaccination in Cologne), and August 6, 2021, COVID-19 cases occurred in 357 and 27,457 fully vaccinated and unvaccinated residents, respectively. Each COVID-19–positive individual in the vaccinated group (VG) was matched 1:1 by age, sex, and virus type to a COVID-19–positive, unvaccinated individual (control group; CG). The two groups did not differ except for significantly higher proportions of asymptomatic infections and higher average cycle threshold (Ct) scores in the VG.

Among 979 contact persons (CP) in the VG and 802 in the CG, 99 (10%) and 303 (38%) became infected, respectively. The proportion of infected CPs to total CPs per index patient (IP) in the VG and CG was 0.13 and 0.37, respectively. Presence of symptoms and lower Ct scores in IPs were associated with transmission. Regression analysis showed that CPs had 79% lower infection risk if the IP was vaccinated (P<0.001). Among 1621 CPs with known vaccination status, the 439 who were fully vaccinated had significantly lower risk for developing COVID-19 (13% vs. 26%).

Créditos: Comité científico Covid

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