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1.
N Engl J Med ; 386(19): 1804-1816, 2022 05 12.
Artículo en Inglés | MEDLINE | ID: mdl-35263534

RESUMEN

BACKGROUND: Waning of vaccine protection against coronavirus disease 2019 (Covid-19) and the emergence of the omicron (or B.1.1.529) variant of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have led to expedited efforts to scale up booster vaccination. Protection conferred by booster doses of the BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna) vaccines in Qatar, as compared with protection conferred by the two-dose primary series, is unclear. METHODS: We conducted two matched retrospective cohort studies to assess the effectiveness of booster vaccination, as compared with that of a two-dose primary series alone, against symptomatic SARS-CoV-2 infection and Covid-19-related hospitalization and death during a large wave of omicron infections from December 19, 2021, through January 26, 2022. The association of booster status with infection was estimated with the use of Cox proportional-hazards regression models. RESULTS: In a population of 2,239,193 persons who had received at least two doses of BNT162b2 or mRNA-1273 vaccine, those who had also received a booster were matched with persons who had not received a booster. Among the BNT162b2-vaccinated persons, the cumulative incidence of symptomatic omicron infection was 2.4% (95% confidence interval [CI], 2.3 to 2.5) in the booster cohort and 4.5% (95% CI, 4.3 to 4.6) in the nonbooster cohort after 35 days of follow-up. Booster effectiveness against symptomatic omicron infection, as compared with that of the primary series, was 49.4% (95% CI, 47.1 to 51.6). Booster effectiveness against Covid-19-related hospitalization and death due to omicron infection, as compared with the primary series, was 76.5% (95% CI, 55.9 to 87.5). BNT162b2 booster effectiveness against symptomatic infection with the delta (or B.1.617.2) variant, as compared with the primary series, was 86.1% (95% CI, 67.3 to 94.1). Among the mRNA-1273-vaccinated persons, the cumulative incidence of symptomatic omicron infection was 1.0% (95% CI, 0.9 to 1.2) in the booster cohort and 1.9% (95% CI, 1.8 to 2.1) in the nonbooster cohort after 35 days; booster effectiveness against symptomatic omicron infection, as compared with the primary series, was 47.3% (95% CI, 40.7 to 53.3). Few severe Covid-19 cases were noted in the mRNA-1273-vaccinated cohorts. CONCLUSIONS: The messenger RNA (mRNA) boosters were highly effective against symptomatic delta infection, but they were less effective against symptomatic omicron infection. However, with both variants, mRNA boosters led to strong protection against Covid-19-related hospitalization and death. (Funded by Weill Cornell Medicine-Qatar and others.).


Asunto(s)
Vacuna nCoV-2019 mRNA-1273/inmunología , Vacuna BNT162/inmunología , COVID-19 , COVID-19/epidemiología , COVID-19/inmunología , COVID-19/prevención & control , Vacunas contra la COVID-19 , Estudios de Cohortes , Humanos , Inmunización Secundaria , Inmunogenicidad Vacunal , Qatar/epidemiología , ARN Mensajero , Estudios Retrospectivos , SARS-CoV-2 , Eficacia de las Vacunas , Vacunas Sintéticas , Vacunas de ARNm
2.
N Engl J Med ; 387(1): 21-34, 2022 07 07.
Artículo en Inglés | MEDLINE | ID: mdl-35704396

RESUMEN

BACKGROUND: The protection conferred by natural immunity, vaccination, and both against symptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection with the BA.1 or BA.2 sublineages of the omicron (B.1.1.529) variant is unclear. METHODS: We conducted a national, matched, test-negative, case-control study in Qatar from December 23, 2021, through February 21, 2022, to evaluate the effectiveness of vaccination with BNT162b2 (Pfizer-BioNTech) or mRNA-1273 (Moderna), natural immunity due to previous infection with variants other than omicron, and hybrid immunity (previous infection and vaccination) against symptomatic omicron infection and against severe, critical, or fatal coronavirus disease 2019 (Covid-19). RESULTS: The effectiveness of previous infection alone against symptomatic BA.2 infection was 46.1% (95% confidence interval [CI], 39.5 to 51.9). The effectiveness of vaccination with two doses of BNT162b2 and no previous infection was negligible (-1.1%; 95% CI, -7.1 to 4.6), but nearly all persons had received their second dose more than 6 months earlier. The effectiveness of three doses of BNT162b2 and no previous infection was 52.2% (95% CI, 48.1 to 55.9). The effectiveness of previous infection and two doses of BNT162b2 was 55.1% (95% CI, 50.9 to 58.9), and the effectiveness of previous infection and three doses of BNT162b2 was 77.3% (95% CI, 72.4 to 81.4). Previous infection alone, BNT162b2 vaccination alone, and hybrid immunity all showed strong effectiveness (>70%) against severe, critical, or fatal Covid-19 due to BA.2 infection. Similar results were observed in analyses of effectiveness against BA.1 infection and of vaccination with mRNA-1273. CONCLUSIONS: No discernable differences in protection against symptomatic BA.1 and BA.2 infection were seen with previous infection, vaccination, and hybrid immunity. Vaccination enhanced protection among persons who had had a previous infection. Hybrid immunity resulting from previous infection and recent booster vaccination conferred the strongest protection. (Funded by Weill Cornell Medicine-Qatar and others.).


Asunto(s)
Vacuna nCoV-2019 mRNA-1273 , Vacuna BNT162 , COVID-19 , Inmunidad Innata , Inmunización , SARS-CoV-2 , Vacuna nCoV-2019 mRNA-1273/inmunología , Vacuna nCoV-2019 mRNA-1273/uso terapéutico , Vacuna BNT162/inmunología , Vacuna BNT162/uso terapéutico , COVID-19/inmunología , COVID-19/prevención & control , COVID-19/virología , Estudios de Casos y Controles , Humanos , Inmunidad Innata/inmunología , Inmunización Secundaria , Recurrencia , SARS-CoV-2/inmunología , Vacunación
3.
N Engl J Med ; 387(20): 1865-1876, 2022 11 17.
Artículo en Inglés | MEDLINE | ID: mdl-36322837

RESUMEN

BACKGROUND: The BNT162b2 vaccine against coronavirus disease 2019 (Covid-19) has been authorized for use in children 5 to 11 years of age and adolescents 12 to 17 years of age but in different antigen doses. METHODS: We assessed the real-world effectiveness of the BNT162b2 vaccine against infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among children and adolescents in Qatar. To compare the incidence of SARS-CoV-2 infection in the national cohort of vaccinated participants with the incidence in the national cohort of unvaccinated participants, we conducted three matched, retrospective, target-trial, cohort studies - one assessing data obtained from children 5 to 11 years of age after the B.1.1.529 (omicron) variant became prevalent and two assessing data from adolescents 12 to 17 years of age before the emergence of the omicron variant (pre-omicron study) and after the omicron variant became prevalent. Associations were estimated with the use of Cox proportional-hazards regression models. RESULTS: Among children, the overall effectiveness of the 10-µg primary vaccine series against infection with the omicron variant was 25.7% (95% confidence interval [CI], 10.0 to 38.6). Effectiveness was highest (49.6%; 95% CI, 28.5 to 64.5) right after receipt of the second dose but waned rapidly thereafter and was negligible after 3 months. Effectiveness was 46.3% (95% CI, 21.5 to 63.3) among children 5 to 7 years of age and 16.6% (95% CI, -4.2 to 33.2) among those 8 to 11 years of age. Among adolescents, the overall effectiveness of the 30-µg primary vaccine series against infection with the omicron variant was 30.6% (95% CI, 26.9 to 34.1), but many adolescents had been vaccinated months earlier. Effectiveness waned over time since receipt of the second dose. Effectiveness was 35.6% (95% CI, 31.2 to 39.6) among adolescents 12 to 14 years of age and 20.9% (95% CI, 13.8 to 27.4) among those 15 to 17 years of age. In the pre-omicron study, the overall effectiveness of the 30-µg primary vaccine series against SARS-CoV-2 infection among adolescents was 87.6% (95% CI, 84.0 to 90.4) and waned relatively slowly after receipt of the second dose. CONCLUSIONS: Vaccination in children was associated with modest, rapidly waning protection against omicron infection. Vaccination in adolescents was associated with stronger, more durable protection, perhaps because of the larger antigen dose. (Funded by Weill Cornell Medicine-Qatar and others.).


Asunto(s)
Vacuna BNT162 , COVID-19 , Eficacia de las Vacunas , Adolescente , Niño , Humanos , Vacuna BNT162/administración & dosificación , Vacuna BNT162/uso terapéutico , COVID-19/epidemiología , COVID-19/prevención & control , Vacunas contra la COVID-19/administración & dosificación , Vacunas contra la COVID-19/uso terapéutico , Qatar/epidemiología , Estudios Retrospectivos , SARS-CoV-2 , Preescolar , Eficacia de las Vacunas/estadística & datos numéricos
4.
N Engl J Med ; 385(24): e83, 2021 12 09.
Artículo en Inglés | MEDLINE | ID: mdl-34614327

RESUMEN

BACKGROUND: Waning of vaccine protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or coronavirus disease 2019 (Covid-19) is a concern. The persistence of BNT162b2 (Pfizer-BioNTech) vaccine effectiveness against infection and disease in Qatar, where the B.1.351 (or beta) and B.1.617.2 (or delta) variants have dominated incidence and polymerase-chain-reaction testing is done on a mass scale, is unclear. METHODS: We used a matched test-negative, case-control study design to estimate vaccine effectiveness against any SARS-CoV-2 infection and against any severe, critical, or fatal case of Covid-19, from January 1 to September 5, 2021. RESULTS: Estimated BNT162b2 effectiveness against any SARS-CoV-2 infection was negligible in the first 2 weeks after the first dose. It increased to 36.8% (95% confidence interval [CI], 33.2 to 40.2) in the third week after the first dose and reached its peak at 77.5% (95% CI, 76.4 to 78.6) in the first month after the second dose. Effectiveness declined gradually thereafter, with the decline accelerating after the fourth month to reach approximately 20% in months 5 through 7 after the second dose. Effectiveness against symptomatic infection was higher than effectiveness against asymptomatic infection but waned similarly. Variant-specific effectiveness waned in the same pattern. Effectiveness against any severe, critical, or fatal case of Covid-19 increased rapidly to 66.1% (95% CI, 56.8 to 73.5) by the third week after the first dose and reached 96% or higher in the first 2 months after the second dose; effectiveness persisted at approximately this level for 6 months. CONCLUSIONS: BNT162b2-induced protection against SARS-CoV-2 infection appeared to wane rapidly following its peak after the second dose, but protection against hospitalization and death persisted at a robust level for 6 months after the second dose. (Funded by Weill Cornell Medicine-Qatar and others.).


Asunto(s)
Vacuna BNT162/inmunología , COVID-19/prevención & control , Inmunogenicidad Vacunal , Eficacia de las Vacunas , Vacuna nCoV-2019 mRNA-1273 , Adulto , Anciano , COVID-19/epidemiología , COVID-19/inmunología , COVID-19/mortalidad , Vacunas contra la COVID-19 , Estudios de Casos y Controles , Femenino , Humanos , Inmunización Secundaria , Masculino , Persona de Mediana Edad , Qatar/epidemiología , Factores de Tiempo , Adulto Joven
5.
Am J Epidemiol ; 2023 Dec 07.
Artículo en Inglés | MEDLINE | ID: mdl-38061757

RESUMEN

The COVID-19 pandemic has highlighted the need to use infection testing databases to rapidly estimate effectiveness of prior infection in preventing reinfection ($P{E}_S$) by novel SARS-CoV-2 variants. Mathematical modeling was used to demonstrate a theoretical foundation for applicability of the test-negative, case-control study design to derive $P{E}_S$. Apart from the very early phase of an epidemic, the difference between the test-negative estimate for $P{E}_S$ and true value of $P{E}_S$ was minimal and became negligible as the epidemic progressed. The test-negative design provided robust estimation of $P{E}_S$ and its waning. Assuming that only 25% of prior infections are documented, misclassification of prior infection status underestimated $P{E}_S$, but the underestimate was considerable only when >50% of the population was ever infected. Misclassification of latent infection, misclassification of current active infection, and scale-up of vaccination all resulted in negligible bias in estimated $P{E}_S$. The test-negative design was applied to national-level testing data in Qatar to estimate $P{E}_S$ for SARS-CoV-2. $P{E}_S$ against SARS-CoV-2 Alpha and Beta variants was estimated at 97.0% (95% CI: 93.6-98.6) and 85.5% (95% CI: 82.4-88.1), respectively. These estimates were validated using a cohort study design. The test-negative design offers a feasible, robust method to estimate protection from prior infection in preventing reinfection.

6.
Clin Infect Dis ; 75(1): e1188-e1191, 2022 08 24.
Artículo en Inglés | MEDLINE | ID: mdl-34657152

RESUMEN

Beta (B.1.351)-variant coronavirus disease 2019 (COVID-19) disease was investigated in Qatar. Compared with the Alpha (B.1.1.7) variant, odds (95% confidence interval) of progressing to severe disease, critical disease, and COVID-19-related death were 1.24-fold (1.11-1.39), 1.49-fold (1.13-1.97), and 1.57-fold (1.03-2.43) higher, respectively, for the Beta variant.


Asunto(s)
COVID-19 , SARS-CoV-2 , Humanos , SARS-CoV-2/genética
7.
Clin Infect Dis ; 73(7): e1830-e1840, 2021 10 05.
Artículo en Inglés | MEDLINE | ID: mdl-33315061

RESUMEN

BACKGROUND: Risk of reinfection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is unknown. We assessed the risk and incidence rate of documented SARS-CoV-2 reinfection in a cohort of laboratory-confirmed cases in Qatar. METHODS: All SARS-CoV-2 laboratory-confirmed cases with at least 1 polymerase chain reaction-positive swab that was ≥45 days after a first positive swab were individually investigated for evidence of reinfection. Viral genome sequencing of the paired first positive and reinfection viral specimens was conducted to confirm reinfection. RESULTS: Out of 133 266 laboratory-confirmed SARS-CoV-2 cases, 243 persons (0.18%) had at least 1 subsequent positive swab ≥45 days after the first positive swab. Of these, 54 cases (22.2%) had strong or good evidence for reinfection. Median time between the first swab and reinfection swab was 64.5 days (range, 45-129). Twenty-three of the 54 cases (42.6%) were diagnosed at a health facility, suggesting presence of symptoms, while 31 (57.4%) were identified incidentally through random testing campaigns/surveys or contact tracing. Only 1 person was hospitalized at the time of reinfection but was discharged the next day. No deaths were recorded. Viral genome sequencing confirmed 4 reinfections of 12 cases with available genetic evidence. Reinfection risk was estimated at 0.02% (95% confidence interval [CI], .01%-.02%), and reinfection incidence rate was 0.36 (95% CI, .28-.47) per 10 000 person-weeks. CONCLUSIONS: SARS-CoV-2 reinfection can occur but is a rare phenomenon suggestive of protective immunity against reinfection that lasts for at least a few months post primary infection.


Asunto(s)
COVID-19 , SARS-CoV-2 , Trazado de Contacto , Humanos , Incidencia , Reinfección
8.
Emerg Infect Dis ; 27(5): 1343-1352, 2021 05.
Artículo en Inglés | MEDLINE | ID: mdl-33900174

RESUMEN

We investigated what proportion of the population acquired severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and whether the herd immunity threshold has been reached in 10 communities in Qatar. The study included 4,970 participants during June 21-September 9, 2020. Antibodies against SARS-CoV-2 were detected by using an electrochemiluminescence immunoassay. Seropositivity ranged from 54.9% (95% CI 50.2%-59.4%) to 83.8% (95% CI 79.1%-87.7%) across communities and showed a pooled mean of 66.1% (95% CI 61.5%-70.6%). A range of other epidemiologic measures indicated that active infection is rare, with limited if any sustainable infection transmission for clusters to occur. Only 5 infections were ever severe and 1 was critical in these young communities; infection severity rate of 0.2% (95% CI 0.1%-0.4%). Specific communities in Qatar have or nearly reached herd immunity for SARS-CoV-2 infection: 65%-70% of the population has been infected.


Asunto(s)
COVID-19 , SARS-CoV-2 , Humanos , Inmunidad Colectiva , Qatar/epidemiología
9.
PLoS Med ; 18(12): e1003879, 2021 12.
Artículo en Inglés | MEDLINE | ID: mdl-34914711

RESUMEN

BACKGROUND: The epidemiology of the SARS-CoV-2 B.1.1.7 (or Alpha) variant is insufficiently understood. This study's objective was to describe the introduction and expansion of this variant in Qatar and to estimate the efficacy of natural infection against reinfection with this variant. METHODS AND FINDINGS: Reinfections with the B.1.1.7 variant and variants of unknown status were investigated in a national cohort of 158,608 individuals with prior PCR-confirmed infections and a national cohort of 42,848 antibody-positive individuals. Infections with B.1.1.7 and variants of unknown status were also investigated in a national comparator cohort of 132,701 antibody-negative individuals. B.1.1.7 was first identified in Qatar on 25 December 2020. Sudden, large B.1.1.7 epidemic expansion was observed starting on 18 January 2021, triggering the onset of epidemic's second wave, 7 months after the first wave. B.1.1.7 was about 60% more infectious than the original (wild-type) circulating variants. Among persons with a prior PCR-confirmed infection, the efficacy of natural infection against reinfection was estimated to be 97.5% (95% CI: 95.7% to 98.6%) for B.1.1.7 and 92.2% (95% CI: 90.6% to 93.5%) for variants of unknown status. Among antibody-positive persons, the efficacy of natural infection against reinfection was estimated to be 97.0% (95% CI: 92.5% to 98.7%) for B.1.1.7 and 94.2% (95% CI: 91.8% to 96.0%) for variants of unknown status. A main limitation of this study is assessment of reinfections based on documented PCR-confirmed reinfections, but other reinfections could have occurred and gone undocumented. CONCLUSIONS: In this study, we observed that introduction of B.1.1.7 into a naïve population can create a major epidemic wave, but natural immunity in those previously infected was strongly associated with limited incidence of reinfection by B.1.1.7 or other variants.


Asunto(s)
COVID-19/epidemiología , COVID-19/virología , Reinfección/epidemiología , Reinfección/virología , SARS-CoV-2 , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Número Básico de Reproducción , Niño , Femenino , Humanos , Inmunidad Innata , Masculino , Persona de Mediana Edad , Modelos Teóricos , Reacción en Cadena de la Polimerasa , Qatar/epidemiología , Estudios Retrospectivos , Factores de Tiempo , Adulto Joven
11.
JAMA ; 326(19): 1930-1939, 2021 11 16.
Artículo en Inglés | MEDLINE | ID: mdl-34724027

RESUMEN

Importance: The effect of prior SARS-CoV-2 infection on vaccine protection remains poorly understood. Objective: To assess protection from SARS-CoV-2 breakthrough infection after mRNA vaccination among persons with vs without prior SARS-CoV-2 infection. Design, Setting, and Participants: Matched-cohort studies in Qatar for the BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna) vaccines. A total of 1 531 736 individuals vaccinated with either vaccine between December 21, 2020, and September 19, 2021, were followed up beginning 14 days after receiving the second dose until September 19, 2021. Exposures: Prior SARS-CoV-2 infection and COVID-19 vaccination. Main Outcomes and Measures: Incident SARS-CoV-2 infection, defined as a polymerase chain reaction (PCR)-positive nasopharyngeal swab regardless of reason for PCR testing or presence of symptoms. Cumulative incidence was calculated using the Kaplan-Meier estimator method. Results: The BNT162b2-vaccinated cohort comprised 99 226 individuals with and 290 432 matched individuals without prior PCR-confirmed infection (median age, 37 years; 68% male). The mRNA-1273-vaccinated cohort comprised 58 096 individuals with and 169 514 matched individuals without prior PCR-confirmed infection (median age, 36 years; 73% male). Among BNT162b2-vaccinated persons, 159 reinfections occurred in those with and 2509 in those without prior infection 14 days or more after dose 2. Among mRNA-1273-vaccinated persons, 43 reinfections occurred in those with and 368 infections in those without prior infection. Cumulative infection incidence among BNT162b2-vaccinated individuals was an estimated 0.15% (95% CI, 0.12%-0.18%) in those with and 0.83% (95% CI, 0.79%-0.87%) in those without prior infection at 120 days of follow-up (adjusted hazard ratio for breakthrough infection with prior infection, 0.18 [95% CI, 0.15-0.21]; P < .001). Cumulative infection incidence among mRNA-1273-vaccinated individuals was an estimated 0.11% (95% CI, 0.08%-0.15%) in those with and 0.35% (95% CI, 0.32%-0.40%) in those without prior infection at 120 days of follow-up (adjusted hazard ratio, 0.35 [95% CI, 0.25-0.48]; P < .001). Vaccinated individuals with prior infection 6 months or more before dose 1 had statistically significantly lower risk for breakthrough infection than those vaccinated less than 6 months before dose 1 (adjusted hazard ratio, 0.62 [95% CI, 0.42-0.92]; P = .02 for BNT162b2 and 0.40 [95% CI, 0.18-0.91]; P = .03 for mRNA-1273 vaccination). Conclusions and Relevance: Prior SARS-CoV-2 infection was associated with a statistically significantly lower risk for breakthrough infection among individuals receiving the BNT162b2 or mRNA-1273 vaccines in Qatar between December 21, 2020, and September 19, 2021. The observational study design precludes direct comparisons of infection risk between the 2 vaccines.


Asunto(s)
Vacunas contra la COVID-19 , COVID-19/complicaciones , Vacuna nCoV-2019 mRNA-1273 , Adulto , Anciano , Vacuna BNT162 , COVID-19/diagnóstico , COVID-19/prevención & control , Prueba de Ácido Nucleico para COVID-19 , Estudios de Cohortes , Femenino , Humanos , Masculino , Persona de Mediana Edad , Qatar
15.
J Med Virol ; 92(3): 386-393, 2020 03.
Artículo en Inglés | MEDLINE | ID: mdl-31663611

RESUMEN

This study aimed to investigate the epidemiology of hepatitis C virus (HCV) genotypes in the Middle East and North Africa (MENA) through an analytical and quantitative meta-regression methodology. For the most common genotypes 1, 3, and 4, country/subregion explained more than 77% of the variation in the distribution of each genotype. Genotype 1 was common across MENA, and was more present in high-risk clinical populations than in the general population. Genotype 3 was much more present in Afghanistan, Iran, and Pakistan than the rest of countries, and was associated with transmission through injecting drug use. Genotype 4 was broadly disseminated in Egypt in all populations, with overall limited presence elsewhere. While genotype 2 was more present in high-risk clinical populations and people who inject drugs, most of the variation in its distribution remained unexplained. Genotypes 5, 6, and 7 had low or no presence in MENA, limiting the epidemiological inferences that could be drawn. To sum up, geography is the principal determinant of HCV genotype distribution. Genotype 1 is associated with transmission through high-risk clinical procedures, while genotype 3 is associated with injecting drug use. These findings demonstrate the power of such analytical approach, which if extended to other regions and globally, can yield relevant epidemiological inferences.


Asunto(s)
Genotipo , Hepacivirus/genética , Hepatitis C/epidemiología , África del Norte/epidemiología , Consumidores de Drogas/estadística & datos numéricos , Métodos Epidemiológicos , Geografía , Hepatitis C/virología , Humanos , Medio Oriente/epidemiología , Prevalencia , Factores de Riesgo
16.
BMC Infect Dis ; 19(1): 809, 2019 Sep 14.
Artículo en Inglés | MEDLINE | ID: mdl-31521121

RESUMEN

BACKGROUND: With one in every 20 Pakistanis already infected, Pakistan has the second largest number of hepatitis C virus (HCV) infections globally. The aim of this study was to present a quantitative and analytical characterization of the HCV epidemic in Pakistan. METHODS: A standardized database of HCV antibody incidence and prevalence and HCV genotypes in all subpopulations was systematically assembled. Random-effects meta-analyses and random-effects meta-regressions were performed. Shannon Diversity Index was calculated to determine genotype diversity. RESULTS: The database included two incidence, 309 prevalence, and 48 genotype measures. Pooled mean HCV prevalence ranged between 7.0% (95% confidence interval (CI): 5.8-8.3%) in Sindh and 0.9% (95% CI: 0.1-2.4%) in Federally Administered Tribal Areas (F.A.T.A). Estimated number of chronically-infected persons ranged between 4.2 million in Punjab and 0.03 million in F.A.T.A. HCV prevalence was stable over time [adjusted odds ratio (AOR) of 1.0 (95% CI: 1.0-1.0)]. Population classification was the strongest predictor of HCV prevalence, explaining 51.8% of prevalence variation. Relative to the general population, HCV prevalence was higher in people who inject drugs [AOR of 23.8 (95% CI: 13.0-43.6)], populations with liver-related conditions [AOR of 22.3 (95% CI: 15.7-31.6)], and high-risk clinical populations [AOR of 7.8 (95% CI: 4.8-12.7)]. Low genotype diversity was observed (Shannon diversity index of 0.67 out of 1.95; 34.5%). There were only minor differences in genotype diversity by province, with genotype 3 being most common in all provinces. CONCLUSION: Pakistan's HCV epidemic shows homogeneity across the provinces, and over time. HCV prevalence is strikingly persistent at high level, with no evidence for a decline over the last three decades. Scale up of HCV treatment and prevention is urgently needed.


Asunto(s)
Epidemias/estadística & datos numéricos , Hepacivirus/genética , Hepatitis C/epidemiología , Antivirales/uso terapéutico , Variación Genética , Genotipo , Hepatitis C/tratamiento farmacológico , Anticuerpos contra la Hepatitis C/análisis , Humanos , Incidencia , Análisis Multivariante , Oportunidad Relativa , Pakistán/epidemiología , Prevalencia , Factores de Riesgo , Pruebas Serológicas
17.
J Med Virol ; 90(1): 131-141, 2018 01.
Artículo en Inglés | MEDLINE | ID: mdl-28842995

RESUMEN

Our objective was to characterize the distribution, diversity and patterns of hepatitis C virus (HCV) genotypes in the Middle East and North Africa (MENA). Source of data was a database of HCV genotype studies in MENA populated using a series of systematic literature searches. Pooled mean proportions were estimated for each genotype and by country using DerSimonian-Laird random-effects meta-analyses. Genotype diversity within countries was assessed using Shannon Diversity Index. Number of chronic infections by genotype and country was calculated using the pooled proportions and country-specific numbers of chronic infection. Analyses were conducted on 338 genotype studies including 82 257 genotyped individuals. Genotype 1 was dominant (≥50%) in Algeria, Iran, Morocco, Oman, Tunisia, and UAE, and was overall ubiquitous across the region. Genotype 2 was common (10-50%) in Algeria, Bahrain, Libya, and Morocco. Genotype 3 was dominant in Afghanistan and Pakistan. Genotype 4 was dominant in Egypt, Iraq, Jordan, Palestine, Qatar, Saudi Arabia, and Syria. Genotypes 5, 6, and 7 had limited or no presence across countries. Genotype diversity varied immensely throughout MENA. Weighted by population size, MENA's chronic infections were highest among genotype 3, followed by genotype 4, genotype 1, genotype 2, genotype 5, and genotype 6. Despite ubiquitous presence of genotype 1, the vast majority of chronic infections were of genotypes 3 or 4, because of the sizable epidemics in Pakistan and Egypt. Three sub-regional patterns were identified: genotype 3 pattern centered in Pakistan, genotype 4 pattern centered in Egypt, and genotype 1 pattern ubiquitous in most MENA countries.


Asunto(s)
Variación Genética , Hepacivirus/genética , Hepatitis C Crónica/epidemiología , Hepatitis C/epidemiología , Hepatitis C/virología , África del Norte/epidemiología , Femenino , Genotipo , Hepacivirus/clasificación , Hepatitis C/transmisión , Hepatitis C Crónica/transmisión , Hepatitis C Crónica/virología , Humanos , Masculino , Medio Oriente/epidemiología , Embarazo
18.
Thorax ; 69(11): 1005-14, 2014 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-25112730

RESUMEN

BACKGROUND: This study aimed to assess associations of outdoor air pollution on prevalence of chronic bronchitis symptoms in adults in five cohort studies (Asthma-E3N, ECRHS, NSHD, SALIA, SAPALDIA) participating in the European Study of Cohorts for Air Pollution Effects (ESCAPE) project. METHODS: Annual average particulate matter (PM(10), PM(2.5), PM(absorbance), PM(coarse)), NO(2), nitrogen oxides (NO(x)) and road traffic measures modelled from ESCAPE measurement campaigns 2008-2011 were assigned to home address at most recent assessments (1998-2011). Symptoms examined were chronic bronchitis (cough and phlegm for ≥3 months of the year for ≥2 years), chronic cough (with/without phlegm) and chronic phlegm (with/without cough). Cohort-specific cross-sectional multivariable logistic regression analyses were conducted using common confounder sets (age, sex, smoking, interview season, education), followed by meta-analysis. RESULTS: 15 279 and 10 537 participants respectively were included in the main NO(2) and PM analyses at assessments in 1998-2011. Overall, there were no statistically significant associations with any air pollutant or traffic exposure. Sensitivity analyses including in asthmatics only, females only or using back-extrapolated NO(2) and PM10 for assessments in 1985-2002 (ECRHS, NSHD, SALIA, SAPALDIA) did not alter conclusions. In never-smokers, all associations were positive, but reached statistical significance only for chronic phlegm with PM(coarse) OR 1.31 (1.05 to 1.64) per 5 µg/m(3) increase and PM(10) with similar effect size. Sensitivity analyses of older cohorts showed increased risk of chronic cough with PM(2.5abs) (black carbon) exposures. CONCLUSIONS: Results do not show consistent associations between chronic bronchitis symptoms and current traffic-related air pollution in adult European populations.


Asunto(s)
Bronquitis Crónica , Contaminación del Aire/efectos adversos , Bronquitis Crónica/epidemiología , Bronquitis Crónica/etiología , Bronquitis Crónica/prevención & control , Estudios de Cohortes , Estudios Transversales , Monitoreo del Ambiente , Salud Global , Humanos , Incidencia , Factores de Riesgo
19.
Front Med (Lausanne) ; 11: 1363045, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38529118

RESUMEN

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.

20.
Vaccine ; 42(14): 3307-3320, 2024 May 22.
Artículo en Inglés | MEDLINE | ID: mdl-38616439

RESUMEN

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.


Asunto(s)
Vacuna nCoV-2019 mRNA-1273 , Vacuna BNT162 , Vacunas contra la COVID-19 , COVID-19 , SARS-CoV-2 , Eficacia de las Vacunas , Humanos , COVID-19/prevención & control , COVID-19/inmunología , Vacuna BNT162/inmunología , Vacuna BNT162/administración & dosificación , Qatar/epidemiología , SARS-CoV-2/inmunología , Masculino , Vacuna nCoV-2019 mRNA-1273/inmunología , Persona de Mediana Edad , Vacunas contra la COVID-19/inmunología , Vacunas contra la COVID-19/administración & dosificación , Femenino , Adulto , Estudios de Casos y Controles , Adulto Joven , Adolescente , Anciano , Índice de Severidad de la Enfermedad , Vacunación/métodos
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