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. 2023 Nov;17(11):e13224.
doi: 10.1111/irv.13224.

SARS-CoV-2 infection and effects of age, sex, comorbidity, and vaccination among older individuals: A national cohort study

Mai A Mahmoud  1 , Houssein H Ayoub  2 , Peter Coyle  3   4   5 , Patrick Tang  6 , Mohammad R Hasan  7 , Hadi M Yassine  8   9 , Asmaa A Al Thani  8   9 , Zaina Al-Kanaani  3 , Einas Al-Kuwari  3 , Andrew Jeremijenko  3 , Anvar Hassan Kaleeckal  3 , Ali Nizar Latif  3 , Riyazuddin Mohammad Shaik  3 , Hanan F Abdul-Rahim  9 , Gheyath K Nasrallah  8   9 , Mohamed Ghaith Al-Kuwari  10 , Adeel A Butt  3   11   12 , Hamad Eid Al-Romaihi  13 , Mohamed H Al-Thani  13 , Abdullatif Al-Khal  3 , Roberto Bertollini  13 , Laith J Abu-Raddad  9   12   14   15   16 , Hiam Chemaitelly  12   14   15
Affiliations

SARS-CoV-2 infection and effects of age, sex, comorbidity, and vaccination among older individuals: A national cohort study

Mai A Mahmoud et al. Influenza Other Respir Viruses. 2023 Nov.

Abstract

Background: We investigated the contribution of age, coexisting medical conditions, sex, and vaccination to incidence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and of severe, critical, or fatal COVID-19 in older adults since pandemic onset.

Methods: A national retrospective cohort study was conducted in the population of Qatar aged ≥50 years between February 5, 2020 and June 15, 2023. Adjusted hazard ratios (AHRs) for infection and for severe coronavirus disease 2019 (COVID-19) outcomes were estimated through Cox regression models.

Results: Cumulative incidence was 25.01% (95% confidence interval [CI]: 24.86-25.15%) for infection and 1.59% (95% CI: 1.55-1.64%) for severe, critical, or fatal COVID-19 after a follow-up duration of 40.9 months. Risk of infection varied minimally by age and sex but increased significantly with coexisting conditions. Risk of infection was reduced with primary-series vaccination (AHR: 0.91, 95% CI: 0.90-0.93) and further with first booster vaccination (AHR: 0.75, 95% CI: 0.74-0.77). Risk of severe, critical, or fatal COVID-19 increased exponentially with age and linearly with coexisting conditions. AHRs for severe, critical, or fatal COVID-19 were 0.86 (95% CI: 0.7-0.97) for one dose, 0.15 (95% CI: 0.13-0.17) for primary-series vaccination, and 0.11 (95% CI: 0.08-0.14) for first booster vaccination. Sensitivity analysis restricted to only Qataris yielded similar results.

Conclusion: Incidence of severe COVID-19 in older adults followed a dynamic pattern shaped by infection incidence, variant severity, and population immunity. Age, sex, and coexisting conditions were strong determinants of infection severity. Vaccine protection against severe outcomes showed a dose-response relationship, highlighting the importance of booster vaccination for older adults.

Keywords: COVID-19; Qatar; geriatrics; immunity; older adults; vaccination.

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Conflict of interest statement

Dr. Butt has received institutional grant funding from Gilead Sciences unrelated to the work presented in this paper. Otherwise, we declare no conflict of interest.

Figures

FIGURE 1
FIGURE 1
Flowchart illustrating the selection process of the study population.
FIGURE 2
FIGURE 2
Cumulative incidence of (A) SARS‐CoV‐2 infection and (B) severe, critical, or fatal COVID‐19 disease over the duration of the study.
FIGURE 3
FIGURE 3
Adjusted hazard ratios against SARS‐CoV‐2 infection across (A) age, (B) number of coexisting conditions, (C) sex, and (D) vaccination dose status.
FIGURE 4
FIGURE 4
Adjusted hazard ratios against severe, critical, or fatal COVID‐19 disease across (A) age, (B) number of coexisting conditions, (C) sex, and (D) vaccination dose status.
See this image and copyright information in PMC

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