BACKGROUND: COVID-19 continues to spread throughout the world. Real-time reverse transcriptase polymerase chain reaction (RT-PCR) is used to diagnose COVID-19, with its cycle threshold (Ct) value inversely related to the viral load. The association between Ct values and COVID-19 related outcomes has been studied in the hospital setting but less so in the community. We aimed to estimate the association between Ct values and the severity of community-diagnosed COVID-19 to provide evidence on the utility of Ct testing in this setting.

METHODS: This was a retrospective cohort study based on data from Israel's largest health organization. The study population included 34,658 individuals who tested positive for COVID-19 by RT-PCR and had available Ct values between June 1st and December 21st, 2020. Outcomes included COVID-19 related symptoms, hospitalization, severe disease, and death. Ct values were modelled both as discrete and continuous exposures.

RESULTS: After adjusting for known risk factors for severe COVID-19, low Ct values were associated with symptomatic disease (odds ratio [OR]: 1.51; 95% confidence interval [CI]:1.21-1.84), hospitalization (OR: 1.27; 95%CI: 1.12-1.49), severe disease (OR: 1.80; 95%CI: 1.43-2.27), and death (OR: 1.64; 95%CI: 1.06-2.59). By modelling the exposure as continuous, we noticed a dose-response relationship, with the risk gradually rising with lower Ct values.

CONCLUSIONS: This study found a significant association between low Ct values and severe COVID-19 related outcomes, with a dose-response relationship. This suggests that Ct values could be helpful in identifying high-risk patients diagnosed in the community.

BACKGROUND: COVID-19 continues to spread throughout the world. Real-time reverse transcriptase polymerase chain reaction (RT-PCR) is used to diagnose COVID-19, with its cycle threshold (Ct) value inversely related to the viral load. The association between Ct values and COVID-19 related outcomes has been studied in the hospital setting but less so in the community. We aimed to estimate the association between Ct values and the severity of community-diagnosed COVID-19 to provide evidence on the utility of Ct testing in this setting.

METHODS: This was a retrospective cohort study based on data from Israel's largest health organization. The study population included 34,658 individuals who tested positive for COVID-19 by RT-PCR and had available Ct values between June 1st and December 21st, 2020. Outcomes included COVID-19 related symptoms, hospitalization, severe disease, and death. Ct values were modelled both as discrete and continuous exposures.

RESULTS: After adjusting for known risk factors for severe COVID-19, low Ct values were associated with symptomatic disease (odds ratio [OR]: 1.51; 95% confidence interval [CI]:1.21-1.84), hospitalization (OR: 1.27; 95%CI: 1.12-1.49), severe disease (OR: 1.80; 95%CI: 1.43-2.27), and death (OR: 1.64; 95%CI: 1.06-2.59). By modelling the exposure as continuous, we noticed a dose-response relationship, with the risk gradually rising with lower Ct values.

CONCLUSIONS: This study found a significant association between low Ct values and severe COVID-19 related outcomes, with a dose-response relationship. This suggests that Ct values could be helpful in identifying high-risk patients diagnosed in the community.

To evaluate the effectiveness of the BNT162b2 messenger RNA vaccine in pregnant women, we conducted an observational cohort study of pregnant women aged 16 years or older, with no history of SARS-CoV-2, who were vaccinated between 20 December 2020 and 3 June 2021. A total of 10,861 vaccinated pregnant women were matched to 10,861 unvaccinated pregnant controls using demographic and clinical characteristics. Study outcomes included documented infection with SARS-CoV-2, symptomatic COVID-19, COVID-19-related hospitalization, severe illness and death. Estimated vaccine effectiveness from 7 through to 56 d after the second dose was 96% (95% confidence interval 89-100%) for any documented infection, 97% (91-100%) for infections with documented symptoms and 89% (43-100%) for COVID-19-related hospitalization. Only one event of severe illness was observed in the unvaccinated group and no deaths were observed in either group. In summary, the BNT162b2 mRNA vaccine was estimated to have high vaccine effectiveness in pregnant women, which is similar to the effectiveness estimated in the general population.

To evaluate the effectiveness of the BNT162b2 messenger RNA vaccine in pregnant women, we conducted an observational cohort study of pregnant women aged 16 years or older, with no history of SARS-CoV-2, who were vaccinated between 20 December 2020 and 3 June 2021. A total of 10,861 vaccinated pregnant women were matched to 10,861 unvaccinated pregnant controls using demographic and clinical characteristics. Study outcomes included documented infection with SARS-CoV-2, symptomatic COVID-19, COVID-19-related hospitalization, severe illness and death. Estimated vaccine effectiveness from 7 through to 56 d after the second dose was 96% (95% confidence interval 89-100%) for any documented infection, 97% (91-100%) for infections with documented symptoms and 89% (43-100%) for COVID-19-related hospitalization. Only one event of severe illness was observed in the unvaccinated group and no deaths were observed in either group. In summary, the BNT162b2 mRNA vaccine was estimated to have high vaccine effectiveness in pregnant women, which is similar to the effectiveness estimated in the general population.