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    Effects of SARS-CoV-2 Alpha, Beta, and Delta variants, age, vaccination, and prior infection on infectiousness of SARS-CoV-2 infections

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    Date
    2022-09-13
    Author
    Qassim, Suelen H.
    Hasan, Mohammad R.
    Tang, Patrick
    Chemaitelly, Hiam
    Ayoub, Houssein H.
    Yassine, Hadi M.
    Al-Khatib, Hebah A.
    Smatti, Maria K.
    Abdul-Rahim, Hanan F.
    Nasrallah, Gheyath K.
    Al-Kuwari, Mohamed Ghaith
    Al-Khal, Abdullatif
    Coyle, Peter
    Gillani, Imtiaz
    Kaleeckal, Anvar Hassan
    Shaik, Riyazuddin Mohammad
    Latif, Ali Nizar
    Al-Kuwari, Einas
    Jeremijenko, Andrew
    Butt, Adeel A.
    Bertollini, Roberto
    Al-Romaihi, Hamad Eid
    Al-Thani, Mohamed H.
    Abu-Raddad, Laith J.
    ...show more authors ...show less authors
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    Abstract
    In 2021, Qatar experienced considerable incidence of SARS-CoV-2 infection that was dominated sequentially by the Alpha, Beta, and Delta variants. Using the cycle threshold (Ct) value of an RT-qPCR-positive test to proxy the inverse of infectiousness, we investigated infectiousness of SARS-CoV-2 infections by variant, age, sex, vaccination status, prior infection status, and reason for testing in a random sample of 18,355 RT-qPCR-genotyped infections. Regression analyses were conducted to estimate associations with the Ct value of RT-qPCR-positive tests. Compared to Beta infections, Alpha and Delta infections demonstrated 2.56 higher Ct cycles (95% CI: 2.35-2.78), and 4.92 fewer cycles (95% CI: 4.67- 5.16), respectively. The Ct value declined gradually with age and was especially high for children <10 years of age, signifying lower infectiousness in small children. Children <10 years of age had 2.18 higher Ct cycles (95% CI: 1.88-2.48) than those 10-19 years of age. Compared to unvaccinated individuals, the Ct value was higher among individuals who had received one or two vaccine doses, but the Ct value decreased gradually with time since the second-dose vaccination. Ct value was 2.07 cycles higher (95% CI: 1.42-2.72) for those with a prior infection than those without prior infection. The Ct value was lowest among individuals tested because of symptoms and was highest among individuals tested as a travel requirement. Delta was substantially more infectious than Beta. Prior immunity, whether due to vaccination or prior infection, is associated with lower infectiousness of breakthrough infections, but infectiousness increases gradually with time since the second-dose vaccination.
    URI
    https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85138859572&origin=inward
    DOI/handle
    http://dx.doi.org/10.3389/fimmu.2022.984784
    http://hdl.handle.net/10576/35599
    Collections
    • Biomedical Research Center Research [‎786‎ items ]
    • Biomedical Sciences [‎802‎ items ]
    • COVID-19 Research [‎848‎ items ]
    • Mathematics, Statistics & Physics [‎786‎ items ]
    • Public Health [‎484‎ items ]

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