ABSTRACT
This study investigated the effectiveness of natural infection in preventing reinfection with the JN.1 variant during a large JN.1 wave in Qatar, using a test-negative case-control study design. The overall effectiveness of previous infection in preventing reinfection with JN.1 was estimated at only 1.8% (95% CI: -9.3-12.6%). This effectiveness demonstrated a rapid decline over time since the previous infection, decreasing from 82.4% (95% CI: 40.9-94.7%) within 3 to less than 6 months after the previous infection to 50.9% (95% CI: -11.8-78.7%) in the subsequent 3 months, and further dropping to 18.3% (95% CI: -34.6-56.3%) in the subsequent 3 months. Ultimately, it reached a negligible level after one year. The findings show that the protection of natural infection against reinfection with JN.1 is strong only among those who were infected within the last 6 months, with variants such as XBB*. However, this protection wanes rapidly and is entirely lost one year after the previous infection. The findings support considerable immune evasion by JN.1.
ABSTRACT
Background: This study assessed the evolution of COVID-19 severity and fatality by utilizing rigorous and standardized criteria that were consistently applied throughout the pandemic in Qatar. Methods: A national cohort study was conducted on Qataris, using data on COVID-19 acute-care and ICU hospitalizations, as well as severe, critical, and fatal COVID-19 cases classified according to the World Health Organization criteria. Results: The cumulative incidence of severe, critical, or fatal COVID-19 after 3.14 years of follow-up was 0.45% (95% CI: 0.43-0.47%). The incidence rate for severe, critical, or fatal COVID-19 throughout the pandemic was 1.43 (95% CI: 1.35-1.50) per 1,000 person-years. In the pre-omicron phase, first omicron wave, and combined phases, it was 2.01 (95% CI: 1.90-2.13), 3.70 (95% CI: 3.25-4.22), and 2.18 (95% CI: 2.07-2.30) per 1,000 person-years, respectively. The post-first omicron phase saw a drastic drop to 0.10 (95% CI: 0.08-0.14) per 1,000 person-years, a 95.4% reduction. Among all severe, critical, and fatal cases, 99.5% occurred during the primary infection. The cumulative incidence of fatal COVID-19 was 0.042% (95% CI: 0.036-0.050%), with an incidence rate of 0.13 (95% CI: 0.11-0.16) per 1,000 person-years. In the post-first omicron phase, the incidence rate of fatal COVID-19 decreased by 90.0% compared to earlier stages. Both severity and fatality exhibited an exponential increase with age and a linear increase with the number of coexisting conditions. Conclusions: The conclusion of the first omicron wave was a turning point in the severity of the pandemic. While vaccination and enhanced case management reduced severity gradually, the rapid accumulation of natural immunity during the initial omicron wave appears to have played the crucial role in driving this shift in severity.
Subject(s)
COVID-19ABSTRACT
Background: Epidemiological evidence for immune imprinting was investigated in immune histories related to vaccination in Qatar from onset of the omicron wave, on December 19, 2021, through September 15, 2022. Methods: Matched, retrospective, cohort studies were conducted to investigate differences in incidence of SARS-CoV-2 reinfection in the national cohort of persons who had a primary omicron infection, but different vaccination histories. History of primary-series (two-dose) vaccination was compared to that of no vaccination, history of booster (three-dose) vaccination was compared to that of two-dose vaccination, and history of booster vaccination was compared to that of no vaccination. Associations were estimated using Cox proportional-hazards regression models. Results: The adjusted hazard ratio comparing incidence of reinfection in the two-dose cohort to that in the unvaccinated cohort was 0.43 (95% CI: 0.38-0.48). The adjusted hazard ratio comparing incidence of reinfection in the three-dose cohort to that in the two-dose cohort was 1.38 (95% CI: 1.16-1.65). The adjusted hazard ratio comparing incidence of reinfection in the three-dose cohort to that in the unvaccinated cohort was 0.53 (95% CI: 0.44-0.63). All adjusted hazard ratios appeared stable over 6 months of follow-up. Divergence in cumulative incidence curves in all comparisons increased markedly when incidence was dominated by BA.4/BA.5 and BA.2.75*. No reinfection in any cohort progressed to severe, critical, or fatal COVID-19. Conclusions: History of primary-series vaccination enhanced immune protection against omicron reinfection, but history of booster vaccination compromised protection against omicron reinfection. These findings do not undermine the short-term public health utility of booster vaccination.
Subject(s)
COVID-19ABSTRACT
The BA.2.75* sublineage of SARS-CoV-2 B.1.1.529 (omicron) variant escapes neutralizing antibodies. We estimated effectiveness of prior infection in preventing reinfection with BA.2.75* using a test-negative, case-control study design. Effectiveness of prior pre-omicron infection against BA.2.75* reinfection, irrespective of symptoms, was 6.0% (95% CI: 1.5-10.4%). Effectiveness of prior BA.1/BA.2 infection was 49.9% (95% CI: 47.6-52.1%) and of prior BA.4/BA.5 infection was 80.6% (95% CI: 71.2-87.0). Effectiveness of prior pre-omicron infection followed by BA.1/BA.2 infection against BA.2.75* reinfection was 56.4% (95% CI: 50.5-61.6). Effectiveness of prior pre-omicron infection followed by BA.4/BA.5 infection was 91.6% (95% CI: 65.1-98.0). Analyses stratified by time since prior infection indicated waning of protection since prior infection. Analyses stratified by vaccination status indicated that protection from prior infection is higher among those vaccinated, particularly among those who combined index-virus-type vaccination with a prior omicron infection. A combination of pre-omicron and omicron immunity is most protective against BA.2.75* reinfection. Viral immune evasion may have accelerated recently to overcome high immunity in the global population, thereby also accelerating waning of natural immunity.
ABSTRACT
Background: There is limited sero epidemiological evidence on the magnitude and long-term durability of antibody titers of mRNA and non-mRNA vaccines in the Qatari population. This study was conducted to generate evidence on long-term anti-S IgG antibodies titers and their dynamics in individuals who have completed a primary COVID-19 vaccination schedule. Methods: A total of 300 participants who received any of the following vaccines BNT162b2/Comirnaty or mRNA-1273 or ChAdOx1-S/Covishield or COVID-19 Vaccine Janssen/Johnson or BBIBP-CorV or Covaxin were enrolled in our study. All sera samples were tested by chemiluminescent microparticle immunoassay (CMIA) for the quantitative determination of IgG antibodies to SARS-CoV-2, receptor-binding domain (RBD) of the S1 subunit of the spike protein of SARS-CoV-2. Antibodies against SARS-CoV-2 nucleocapsid (SARS-CoV-2 N-protein IgG) were also determined. Kaplan-Meier survival curves were used to compare the time from the last dose of the primary vaccination schedule to the time by which anti-S IgG antibodies titers fell into the lowest quartile (range of values collected) for the mRNA and non-mRNA vaccines. Results: Participants vaccinated with mRNA vaccines had higher median anti-S IgG antibody titers. Participants vaccinated with the mRNA-1273 vaccine had the highest median anti-S-antibody level of 13720.9 AU/mL (IQR 6426.5 to 30185.6 AU/mL) followed by BNT162b2 (median, 7570.9 AU/ml; IQR, 3757.9 to 16577.4 AU/mL); while the median anti-S antibody titer for non-mRNA vaccinated participants was 3759.7 AU/mL (IQR, 2059.7-5693.5 AU/mL). The median time to reach the lowest quartile was 3.53 months (IQR, 2.2-4.5 months) and 7.63 months (IQR, 6.3-8.4 months) for the non-mRNA vaccine recipients and Pfizer vaccine recipients, respectively. However, more than 50% of the Moderna vaccine recipients did not reach the lowest quartile by the end of the follow-up period. Conclusions: This evidence on anti-S IgG antibody titers, their durability and decay over time should be considered for the utility of these assays in transmission dynamics after the full course of primary vaccination.
Subject(s)
COVID-19ABSTRACT
Background: The BNT162b2 COVID-19 vaccine is authorized for children 5-11 years of age and adolescents 12-17 years of age, but in different dose sizes. We assessed BNT162b2 real-world effectiveness against SARS-CoV-2 infection among children and adolescents in Qatar. Methods: Three matched, retrospective, target-trial, cohort studies were conducted to compare incidence of SARS-CoV-2 infection in the national cohort of vaccinated individuals to incidence in the national cohort of unvaccinated individuals. Associations were estimated using Cox proportional-hazards regression models. Results: Effectiveness of the 10 micrograms dose for children against Omicron infection was 25.7% (95% CI: 10.0-38.6%). It was highest at 49.6% (95% CI: 28.5-64.5%) right after the second dose, but waned rapidly thereafter and was negligible after 3 months. Effectiveness was 46.3% (95% CI: 21.5-63.3%) among those aged 5-7 years and 16.6% (-4.2-33.2%) among those aged 8-11 years. Effectiveness of the 30 micrograms dose for adolescents against Omicron infection was 30.6% (95% CI: 26.9-34.1%), but many adolescents were vaccinated months earlier. Effectiveness waned with time after the second dose. Effectiveness was 35.6% (95% CI: 31.2-39.6%) among those aged 12-14 years and 20.9% (13.8-27.4%) among those aged 15-17 years. Effectiveness of the 30 micrograms dose for adolescents against pre-Omicron infection was 87.6% (95% CI: 84.0-90.4%) and waned relatively slowly after the second dose. Conclusions: Pediatric vaccination is associated with modest and rapidly waning protection against Omicron infection. Adolescent vaccination is associated with stronger and more durable protection, perhaps because of the larger dose size. Age at such young age appears to play a role in determining vaccine protection, with greater protection observed in younger than older children or adolescents.
Subject(s)
COVID-19ABSTRACT
BackgroundThere is inconclusive evidence whether pregnancy exacerbates COVID-19 symptoms or not, and scarce data from the Middle East and North Africa region. The aim of this study was to investigate the association between pregnancy and COVID-19 symptoms in Qatar. MethodsThis cross-sectional study was carried out using data of all women with confirmed COVID-19, comparing pregnant and non-pregnant women of child-bearing age (18-49 years). Data of all COVID-19 cases were collected by the Ministry of Public Health (MoPH) in Qatar, between March and September 2020. Symptoms were compared by pregnancy status and classified into moderate and severe. Multivariable logistic and poisson regression was carried out to investigate the association between pregnancy and severity of COVID-19 symptoms. ResultsDuring the study period, 105744 individuals were diagnosed with COVID-19, 16908 were women of childbearing age. From that sample, 799 women who were pregnant (mean age 29.9 years (SD 5.2)) and 16109 women who were not pregnant (mean age 33.1 years (SD 7.8)). After multivariable logistic regression, pregnancy was associated with a 1.4-fold higher odds of reporting any symptoms of COVID-19 (OR 1.41, 95% CI 1.18-1.68), and 1.3-fold higher odds of reporting shortness of breath (OR 1.29, 95% CI 1.02-1.63). After multivariable poisson regression, pregnancy was also associated with a higher number of symptoms (IRR 1.03, 95%CI 0.98-1.08). ConclusionOur findings suggest that, in this setting, pregnant women are more likely to have symptomatic COVID-19, and shortness of breath, compared to non-pregnant women of childbearing age.