All-cause and COVID-19 mortality in Qatar during the COVID-19 pandemic

BNT162b2 Versus mRNA-1273 Vaccines: Comparative Analysis of Long-Term Protection Against SARS-CoV-2 Infection and Severe COVID-19 in Qatar

BACKGROUND

This study provides a head-to-head comparison of the protection provided by the BNT162b2 and mRNA-1273 vaccines against SARS-CoV-2 infection and against severe COVID-19, covering primary series and third dose/booster vaccinations over up to 3 years of follow-up, both before and after the emergence of the omicron variant.

METHODS

Two national, matched, retrospective cohort studies were conducted on Qatar's vaccinated population from December 16, 2020, to February 18, 2024. Subgroup analyses by pre-vaccination SARS-CoV-2 infection history, as well as sensitivity analyses, were also conducted.

RESULTS

The adjusted hazard ratio (AHR) comparing infection incidence in those vaccinated with BNT162b2 versus mRNA-1273 was 1.03 (95% CI: 1.02-1.05) after the primary series and 1.11 (95% CI: 1.09-1.13) after the third (booster) dose. The corresponding AHRs for any severe, critical, or fatal COVID-19 were 1.31 (95% CI: 0.81-2.11) and 1.00 (95% CI: 0.20-4.94), respectively. Subgroup analyses by prior infection status hinted at a dose-dependent immune imprinting effect, where a combination of two types of immunity, pre-omicron and omicron, offered greater protection against infection than one type alone, with this effect being amplified by the higher antigen dose of mRNA-1273 compared to BNT162b2. Sensitivity analyses confirmed the study findings.

CONCLUSIONS

BNT162b2 provided slightly less protection against infection than mRNA-1273 following both primary series and booster vaccinations while offering comparable protection against severe COVID-19 outcomes. The findings suggested that the vaccine antigen dose in interaction with infection history may determine the extent of immune protection against infection.

COVID-19 epidemic investigation study of a follow-up cohort of patients with diabetic kidney disease

Introduction

The impact of coronavirus disease 2019 (COVID-19) on diabetic kidney disease (DKD) patients in China is not fully understood. This study aimed to investigate infection status in a DKD cohort post-renal biopsy and analyze vaccination and infection rates, as well as symptom severity, across various renal pathologies in DKD patients.

Methods

This epidemiological survey, centered on COVID-19, employed a Chinese DKD and renal puncture follow-up cohort. A customized questionnaire enabled standardized data gathering. It collected data on clinical characteristics, vaccination and infection statuses, and diverse pathological types. The study analyzed the relationship between vaccination and infection statuses across various pathological types, evaluating characteristics and treatment outcomes in patients with infections.

Results

In total, 437 patients with DKD from 26 Chinese provinces were followed up for a median of 44.6 ± 20 months. COVID-19 infection, vaccination, and novel coronavirus pneumonia (NCP) rates were 73.68%, 59.3%, and 6.63%, respectively. Ten patients with NCP had severe pneumonia or died of COVID-19. Renal pathology revealed that 167 (38.22%) patients had diabetic nephropathy (DN), 171 (39.13%) had non-diabetic renal disease (NDRD), and 99 had DN and NDRD (22.65%). The DN group had the lowest vaccination (54.5%), highest all-cause mortality (3.6%), and highest endpoint rates (34.10%). Compared to patients who were not vaccinated pre-infection (117 cases), vaccinated patients (198 cases) had reduced NCP (6.6% vs. 13.7%), severity (1.0% vs. 3.4%), and endpoint (9.10% vs. 31.60%) rates.

Conclusion

Vaccination can prevent infection and diminish COVID-19 severity in patients with DKD; therefore, increasing vaccination rates is particularly important.

Clinical Trial registration

ClinicalTrails.gov, NCT05888909.

Association between COVID-19 vaccination and stroke: a nationwide case-control study in Qatar

OBJECTIVE

This study investigated the association between Coronavirus Disease 2019 mRNA vaccination and stroke in Qatar.

METHODS

Between December 1, 2020, and April 11, 2023, a matched case-control study was conducted to investigate the association between 3036 acute stroke cases and 3036 controls drawn from the entire population of Qatar.

RESULTS

The adjusted odds ratio (aOR) for vaccination among cases compared to controls was 0.87 (95% CI: 0.75-1.00). The aOR was 0.74 (95% CI: 0.45-1.23) for a single vaccine dose, 0.87 (95% CI: 0.73-1.04) for primary-series vaccination (two doses), and 0.91 (95% CI: 0.66-1.25) for booster vaccination (three or more doses). The aOR was 0.87 (95% CI: 0.72-1.04) for BNT162b2 and 0.86 (95% CI: 0.67-1.11) for mRNA-1273. Subgroup analyses, considering different durations since vaccination, also demonstrated no association. Subgroup analyses based on nationality, age, number of coexisting conditions, or prior infection status yielded similar results. Subgroup analysis, stratified by stroke type, suggested an association between vaccination and cerebral venous sinus thrombosis (aOR of 2.50 [95% CI: 0.97-6.44]), but it did not reach statistical significance.

CONCLUSION

There was no evidence of an increased risk of stroke following vaccination, both in the short term and in the long term, extending beyond a year after receiving the vaccine.

Prevalence of hepatitis A virus among migrant workers in Qatar: A national study

BACKGROUND

Hepatitis A virus (HAV) is the predominant cause of acute viral hepatitis worldwide; however, data on HAV antibody prevalence (seroprevalence) among migrant populations are limited. This study aimed to investigate HAV seroprevalence among Qatar's migrant craft and manual workers (CMWs), constituting approximately 60% of the country's population.

METHODS

HAV antibody testing was conducted on stored serum specimens obtained from CMWs during a nationwide severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) population-based cross-sectional survey between July 26 and September 9, 2020. Associations with HAV infection were investigated through regression analyses.

RESULTS

Of the 2,607 specimens with HAV antibody test results, 2,393 were positive, and 214 were negative. The estimated HAV seroprevalence among CMWs was 92.0% (95% CI: 90.9-93.1%). HAV seroprevalence was generally high but exhibited some variation, ranging from 70.9% (95% CI: 62.4-78.2%) among Sri Lankans to 99.8% (95% CI: 98.2-99.9%) among Pakistanis. The multivariable regression analysis identified age, nationality, and educational attainment as statistically significant factors associated with HAV infection. Relative to CMWs aged ≤29 years, the adjusted relative risk (ARR) was 1.06 (95% CI: 1.03-1.10) in CMWs aged 30-39 years and reached 1.15 (95% CI: 1.10-1.19) in those aged ≥50 years. In comparison to Indians, the ARR was lower among Sri Lankans, assessed at 0.81 (95% CI: 0.72-0.91), but higher among Nepalese at 1.07 (95% CI: 1.04-1.11), Bangladeshis at 1.10 (95% CI: 1.07-1.13), Pakistanis at 1.12 (95% CI: 1.09-1.15), and Egyptians at 1.15 (95% CI: 1.08-1.23). No evidence for differences was found by geographic location or occupation.

CONCLUSIONS

HAV seroprevalence among Qatar's CMW population is very high, with over nine out of every ten individuals having been exposed to this infection, likely during childhood.

COVID-19 testing, incidence, and positivity trends among school age children during the academic years 2020-2022 in the State of Qatar: special focus on using CDC indicators for community transmission to evaluate school attendance policies and public health response

BACKGROUND

There exists a gap in our understanding of the age-dependent epidemiological dynamics of SARS-CoV-2 among school-age children in comparison to adults within the State of Qatar. Additionally, there has been limited assessment of the timely implementation of physical distancing interventions, notably national school closures, and their impact on infection trends.

METHODS

We used the national database to capture all records of polymerase-chain-reaction (PCR) testing, and rapid antigen tests (RAT) conducted at all health care venues in Qatar and administered between August 26, 2020, and August 21, 2022, across all age groups (≥ 5 years old). Study participants under 18 years old were categorized into two age brackets: (5-11) and (12-17), aligning with the Primary and Preparatory/Secondary grade levels in Qatar, respectively. We assessed age group testing rates, incidence rates, and positivity rates in relation to adults. These epidemiological metrics were compared with the CDC's thresholds for COVID-19 community transmission.

RESULTS

Throughout the school years of 2020-2021 and 2021-2022, a total of 5,063,405 and 6,130,531 tests were respectively conducted. In the 2020-2021 school year, 89.6% of the tests were administered to adults, while 13.7% were conducted on children in the following year. The overall test positivity rates for the 2020-2021 and 2021-2022 school years were 5.8% and 8.1%, respectively. Adolescents underwent the fewest tests during the full study period compared to both adults and young children. Using the CDC indicators, we found that children and adolescents can significantly contribute to elevated infection rates, potentially driving community transmission upon relaxation of social restrictions.

CONCLUSION

It is crucial to acknowledge the potential for higher transmission among youth and adolescents when formulating transmission control strategies and making decisions regarding school closures. Employing data-driven indicators and thresholds to monitor COVID-19 community levels is important for informing decision-making. These approaches also enable the prompt implementation of infection control transmission mitigation measures in future pandemics.

Effectiveness of two and three doses of COVID-19 mRNA vaccines against infection, symptoms, and severity in the pre-omicron era: A time-dependent gradient

BACKGROUND

Vaccines were developed and deployed to combat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. This study aimed to characterize patterns in the protection provided by the BNT162b2 and mRNA-1273 mRNA vaccines against a spectrum of SARS-CoV-2 infection symptoms and severities.

METHODS

A national, matched, test-negative, case-control study was conducted in Qatar between January 1 and December 18, 2021, utilizing a sample of 238,896 PCR-positive tests and 6,533,739 PCR-negative tests. Vaccine effectiveness was estimated against asymptomatic, symptomatic, severe coronavirus disease 2019 (COVID-19), critical COVID-19, and fatal COVID-19 infections. Data sources included Qatar's national databases for COVID-19 laboratory testing, vaccination, hospitalization, and death.

RESULTS

Effectiveness of two-dose BNT162b2 vaccination was 75.6% (95% CI: 73.6-77.5) against asymptomatic infection and 76.5% (95% CI: 75.1-77.9) against symptomatic infection. Effectiveness against each of severe, critical, and fatal COVID-19 infections surpassed 90%. Immediately after the second dose, all categories-namely, asymptomatic, symptomatic, severe, critical, and fatal COVID-19-exhibited similarly high effectiveness. However, from 181 to 270 days post-second dose, effectiveness against asymptomatic and symptomatic infections declined to below 40%, while effectiveness against each of severe, critical, and fatal COVID-19 infections remained consistently high. However, estimates against fatal COVID-19 often had wide 95% confidence intervals. Analogous patterns were observed in three-dose BNT162b2 vaccination and two- and three-dose mRNA-1273 vaccination. Sensitivity analyses confirmed the results.

CONCLUSION

A gradient in vaccine effectiveness exists and is linked to the symptoms and severity of infection, providing higher protection against more symptomatic and severe cases. This gradient intensifies over time as vaccine immunity wanes after the last vaccine dose. These patterns appear consistent irrespective of the vaccine type or whether the vaccination involves the primary series or a booster.

Prevalence of hepatitis B and C viruses among migrant workers in Qatar

Limited data exist on viral hepatitis among migrant populations. This study investigated the prevalence of current hepatitis B virus (HBV) infection and lifetime hepatitis C virus (HCV) infection among Qatar's migrant craft and manual workers (CMWs), constituting 60% of the country's population. Sera collected during a nationwide COVID-19 population-based cross-sectional survey on CMWs between July 26 and September 9, 2020, underwent testing for HBsAg and HCV antibodies. Reactive samples underwent confirmatory testing, and logistic regression analyses were employed to explore associations with HBV and HCV infections. Among 2528 specimens tested for HBV infection, 15 were reactive, with 8 subsequently confirmed positive. Three samples lacked sufficient sera for confirmatory testing but were included in the analysis through multiple imputations. Prevalence of current HBV infection was 0.4% (95% CI 0.2-0.7%). Educational attainment and occupation were significantly associated with current HBV infection. For HCV infection, out of 2607 specimens tested, 46 were reactive, and 23 were subsequently confirmed positive. Prevalence of lifetime HCV infection was 0.8% (95% CI 0.5-1.2%). Egyptians exhibited the highest prevalence at 6.5% (95% CI 3.1-13.1%), followed by Pakistanis at 3.1% (95% CI 1.1-8.0%). Nationality, geographic location, and occupation were significantly associated with lifetime HCV infection. HBV infection is relatively low among CMWs, while HCV infection falls within the intermediate range, both compared to global and regional levels.

Addressing bias in the definition of SARS-CoV-2 reinfection: implications for underestimation

Introduction

Reinfections are increasingly becoming a feature in the epidemiology of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. However, accurately defining reinfection poses methodological challenges. Conventionally, reinfection is defined as a positive test occurring at least 90 days after a previous infection diagnosis. Yet, this extended time window may lead to an underestimation of reinfection occurrences. This study investigated the prospect of adopting an alternative, shorter time window for defining reinfection.

Methods

A longitudinal study was conducted to assess the incidence of reinfections in the total population of Qatar, from February 28, 2020 to November 20, 2023. The assessment considered a range of time windows for defining reinfection, spanning from 1 day to 180 days. Subgroup analyses comparing first versus repeat reinfections and a sensitivity analysis, focusing exclusively on individuals who underwent frequent testing, were performed.

Results

The relationship between the number of reinfections in the population and the duration of the time window used to define reinfection revealed two distinct dynamical domains. Within the initial 15 days post-infection diagnosis, almost all positive tests for SARS-CoV-2 were attributed to the original infection. However, surpassing the 30-day post-infection threshold, nearly all positive tests were attributed to reinfections. A 40-day time window emerged as a sufficiently conservative definition for reinfection. By setting the time window at 40 days, the estimated number of reinfections in the population increased from 84,565 to 88,384, compared to the 90-day time window. The maximum observed reinfections were 6 and 4 for the 40-day and 90-day time windows, respectively. The 40-day time window was appropriate for defining reinfection, irrespective of whether it was the first, second, third, or fourth occurrence. The sensitivity analysis, confined to high testers exclusively, replicated similar patterns and results.

Discussion

A 40-day time window is optimal for defining reinfection, providing an informed alternative to the conventional 90-day time window. Reinfections are prevalent, with some individuals experiencing multiple instances since the onset of the pandemic.

Motorcycle-related crashes before and during the COVID-19 pandemic: A comparative retrospective observational study from the Middle East

BACKGROUND

During the COVID-19 pandemic, there was a boom in the delivery sector, with a significant increase in the demand and number of motorcycle delivery drivers in Qatar, which made them vulnerable to injury. We aimed to evaluate the incidence, pattern, and outcome of patients injured by motorcycle-related crashes (MCC) before and during the pandemic.

METHODS

A retrospective observational study included all adult patients admitted with motorcycle-related injuries before the pandemic (March 2018 to February 2020) and during the pandemic (March 2020 to March 2022). Comparative analyses were performed based on (work versus non-work related MCCs) and (pre- versus during the pandemic injuries).

RESULTS

510 patients with MCC were identified, of which 172 (33.7 %) were admitted in the pre-pandemic and 338 (66.3 %) during the pandemic. The mean age of patients was 29.2±7.8 years; 56 % were aged 20-29 years, and 99.4 % were males. Work-related MCCs were more frequent among the younger age group (60.9 % vs. 52.1 %; p=0.001) during the early evening, i.e., 6:00 to 9:00 p.m. (21.9 % vs. 13.9 %; p=0.004). However, non-work related MCC occurred more frequently between midnight and 3:00 am (20.2 % vs. 10.9 %; p=0.004), and such patients were more likely non-compliant for protective devices use (19.3 % vs. 6.1 %; p=0.001) and ride under the influence of alcohol (13.2 % vs. 7.4 %; p=0.03). During the pandemic, the proportion of alcohol consumers (13 % vs. 5.8 %; p=0.01) and work-related MCC (50.9 % vs. 22.7 %; p=0.001) increased significantly compared to the pre-pandemic period.

CONCLUSION

The overall burden of MCC increased during the pandemic, and the frequency of MCC involving commercial drivers surged significantly during the pandemic period as opposed to the non-work MCC, which predominated in the pre-pandemic period. Work-related MCCs were more frequent among younger age groups, mainly involving South Asians with frequent accidents in the evening time. However, recreation-related MCCs occurred more frequently at midnight, and victims were non-compliant with the protective gear. Furthermore, there is a need for prospective studies to examine the broader scope of risk factors that are associated with the work-related MCC, especially involving food deliveries, and for focused safety programs for motorcycle delivery drivers and recreational motorcyclists.

Short- and longer-term all-cause mortality among SARS-CoV-2- infected individuals and the pull-forward phenomenon in Qatar: a national cohort study

OBJECTIVES

We assessed short-, medium-, and long-term all-cause mortality risks after a primary SARS-CoV-2 infection.

METHODS

A national, matched, retrospective cohort study was conducted in Qatar to assess risk of all-cause mortality in the national SARS-CoV-2 primary infection cohort compared with the national infection-naïve cohort. Associations were estimated using Cox proportional-hazards regression models. Analyses were stratified by vaccination status and clinical vulnerability status.

RESULTS

Among unvaccinated persons, within 90 days after primary infection, the adjusted hazard ratio (aHR) comparing mortality incidence in the primary-infection cohort with the infection-naïve cohort was 1.19 (95% confidence interval 1.02-1.39). aHR was 1.34 (1.11-1.63) in persons more clinically vulnerable to severe COVID-19 and 0.94 (0.72-1.24) in those less clinically vulnerable. Beyond 90 days after primary infection, aHR was 0.50 (0.37-0.68); aHR was 0.41 (0.28-0.58) at 3-7 months and 0.76 (0.46-1.26) at ≥8 months. The aHR was 0.37 (0.25-0.54) in more clinically vulnerable persons and 0.77 (0.48-1.24) in less clinically vulnerable persons. Among vaccinated persons, mortality incidence was comparable in the primary-infection versus infection-naïve cohorts, regardless of clinical vulnerability status.

CONCLUSIONS

COVID-19 mortality was primarily driven by an accelerated onset of death among individuals who were already vulnerable to all-cause mortality, but vaccination prevented these accelerated deaths.

History of primary-series and booster vaccination and protection against Omicron reinfection

Laboratory evidence suggests a possibility of immune imprinting for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We investigated the differences in the incidence of SARS-CoV-2 reinfection in a cohort of persons who had a primary Omicron infection, but different vaccination histories using matched, national, retrospective, cohort studies. Adjusted hazard ratio for reinfection incidence, factoring adjustment for differences in testing rate, was 0.43 [95% confidence interval (CI): 0.39 to 0.49] comparing history of two-dose vaccination to no vaccination, 1.47 (95% CI: 1.23 to 1.76) comparing history of three-dose vaccination to two-dose vaccination, and 0.57 (95% CI: 0.48 to 0.68) comparing history of three-dose vaccination to no vaccination. Divergence in cumulative incidence curves increased markedly when the incidence was dominated by BA.4/BA.5 and BA.2.75* Omicron subvariants. The 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 public health utility of booster vaccination.

From past to present: Exploring COVID-19 in Qatar's hemodialysis population across Omicron dominant and pre-Omicron periods

COVID-19 carries a high risk of morbidity and mortality in dialysis patients. Multiple SARS-CoV-2 variants have been identified since the start of the COVID-19 pandemic. The current study aimed to compare the incidence and outcomes of the COVID-19 Omicron dominant period versus other pre-Omicron period in hemodialysis patients. In this observational, analytical, retrospective, nationwide study, we reviewed adult chronic hemodialysis patients between March 1, 2020, and January 31, 2022. Four hundred twenty-one patients had COVID-19 during the study period. The incidence of COVID-19 due to the Omicron dominant period was significantly higher than other pre-Omicron period (30.3% vs. 18.7%, P<0.001). In contrast, the admission rate to ICU was significantly lower in the Omicron dominant period than in the pre-Omicron period (2.8% vs. 25%, P<0001) but with no significant difference in ICU length of stay. The mortality rate was lower in the Omicron dominant period compared to the pre-Omicron period (2.4% vs. 15.5%, P<0.001). Using multivariate analysis, older age [OR 1.093 (95% CI 1.044-1.145); P<0.0001] and need for mechanical ventilation [OR 70.4 (95% CI 20.39-243.1); P<0.0001] were identified as two independent risk factors for death in hemodialysis patients with COVID-19. In Conclusion, the COVID-19 Omicron variant had a higher incidence and lower morbidity and mortality than pre-Omicron period in our hemodialysis population.

Population immunity of natural infection, primary-series vaccination, and booster vaccination in Qatar during the COVID-19 pandemic: an observational study

Background

Waning of natural infection protection and vaccine protection highlight the need to evaluate changes in population immunity over time. Population immunity of previous SARS-CoV-2 infection or of COVID-19 vaccination are defined, respectively, as the overall protection against reinfection or against breakthrough infection at a given point in time in a given population.

Methods

We estimated these population immunities in Qatar's population between July 1, 2020 and November 30, 2022, to discern generic features of the epidemiology of SARS-CoV-2. Effectiveness of previous infection, mRNA primary-series vaccination, and mRNA booster (third-dose) vaccination in preventing infection were estimated, month by month, using matched, test-negative, case-control studies.

Findings

Previous-infection effectiveness against reinfection was strong before emergence of Omicron, but declined with time after a wave and rebounded after a new wave. Effectiveness dropped after Omicron emergence from 88.3% (95% CI: 84.8-91.0%) in November 2021 to 51.0% (95% CI: 48.3-53.6%) in December 2021. Primary-series effectiveness against infection was 84.0% (95% CI: 83.0-85.0%) in April 2021, soon after introduction of vaccination, before waning gradually to 52.7% (95% CI: 46.5-58.2%) by November 2021. Effectiveness declined linearly by ∼1 percentage point every 5 days. After Omicron emergence, effectiveness dropped from 52.7% (95% CI: 46.5-58.2%) in November 2021 to negligible levels in December 2021. Booster effectiveness dropped after Omicron emergence from 83.0% (95% CI: 65.6-91.6%) in November 2021 to 32.9% (95% CI: 26.7-38.5%) in December 2021, and continued to decline thereafter. Effectiveness of previous infection and vaccination against severe, critical, or fatal COVID-19 were generally >80% throughout the study duration.

Interpretation

High population immunity against infection may not be sustained beyond a year, but population immunity against severe COVID-19 is durable with slow waning even after Omicron emergence.

Funding

The Biomedical Research Program and the Biostatistics, Epidemiology, and the Biomathematics Research Core, both at Weill Cornell Medicine-Qatar, Ministry of Public Health, Hamad Medical Corporation, Sidra Medicine, Qatar Genome Programme, Qatar University Biomedical Research Center, and Qatar University Internal Grant ID QUCG-CAS-23/24-114.