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1.
PLoS One ; 17(7): e0271324, 2022.
Article in English | MEDLINE | ID: covidwho-1938448

ABSTRACT

We developed a Coronavirus Disease 2019 (COVID-19) risk score to guide targeted RT-PCR testing in Qatar. The Qatar national COVID-19 testing database, encompassing a total of 2,688,232 RT-PCR tests conducted between February 5, 2020-January 27, 2021, was analyzed. Logistic regression analyses were implemented to derive the COVID-19 risk score, as a tool to identify those at highest risk of having the infection. Score cut-off was determined using the ROC curve based on maximum sum of sensitivity and specificity. The score's performance diagnostics were assessed. Logistic regression analysis identified age, sex, and nationality as significant predictors of infection and were included in the risk score. The ROC curve was generated and the area under the curve was estimated at 0.63 (95% CI: 0.63-0.63). The score had a sensitivity of 59.4% (95% CI: 59.1%-59.7%), specificity of 61.1% (95% CI: 61.1%-61.2%), a positive predictive value of 10.9% (95% CI: 10.8%-10.9%), and a negative predictive value of 94.9% (94.9%-95.0%). The concept and utility of a COVID-19 risk score were demonstrated in Qatar. Such a public health tool can have considerable utility in optimizing testing and suppressing infection transmission, while maximizing efficiency and use of available resources.


Subject(s)
COVID-19 , COVID-19/diagnosis , COVID-19/epidemiology , COVID-19 Testing , Humans , Public Health , Qatar/epidemiology , ROC Curve , Retrospective Studies , Risk Factors , SARS-CoV-2/genetics , Sensitivity and Specificity
2.
J Glob Health ; 12: 05032, 2022 Jul 06.
Article in English | MEDLINE | ID: covidwho-1924590

ABSTRACT

Background: Understanding the disease severity associated with the Omicron variant of the SARS-CoV-2 virus is important in determining appropriate management strategies at the individual and population levels. We determined the severity of SARS-CoV-2 infection in persons infected with the Omicron vs the Delta variant. Methods: We identified individuals with SARS-CoV-2 infection with Delta and propensity-score matched controls with Omicron variant infection from the National COVID-19 Database in Qatar. We excluded temporary visitors to Qatar, those with a prior documented infection, those ≤18 years old, and those with <14 days of follow up after the index test positive date. We determined the rates of admission to the hospital, admission to intensive care unit, mechanical ventilation, or death among those infected with the Delta or Omicron variants. Results: Among 9763 cases infected with the Delta variant and 11 310 cases infected with the Omicron variant, we identified 3926 propensity-score matched pairs. Among 3926 Delta infected, 3259 (83.0%) had mild, 633 (16.1%) had moderate and 34 (0.9%) had severe/critical disease. Among 3926 Omicron infected, 3866 (98.5%) had mild, 59 (1.5%) had moderate, and only 1 had severe/critical disease (overall P < 0.001). Factors associated with less moderate or severe/critical disease included infection with Omicron variant (aOR = 0.06; confidence interval (CI) = 0.05-0.09) and vaccination including a booster (aOR = 0.30; 95% CI = 0.09-0.99). Conclusions: Omicron variant infection is associated with significantly lower severity of disease compared with the Delta variant. Vaccination continues to offer strong protection against severe/critical disease.


Subject(s)
COVID-19 , Adolescent , Humans , Qatar/epidemiology , SARS-CoV-2/genetics , Severity of Illness Index
3.
Lancet HIV ; 9(7): e506-e516, 2022 07.
Article in English | MEDLINE | ID: covidwho-1907940

ABSTRACT

The Middle East and north Africa is one of only two world regions where HIV incidence is on the rise, with most infections occurring among key populations: people who inject drugs, men who have sex with men, and female sex workers. In this Review, we show a trend of increasing HIV prevalence among the three key populations in the Middle East and north Africa. Although the epidemic continues at a low level in some countries or localities within a country, there is evidence for concentrated epidemics, with sustained transmission at considerable HIV prevalence among people who inject drugs and men who have sex with men in over half of countries in the region with data, and among female sex workers in several countries. Most epidemics emerged around 2003 or thereafter. The status of the epidemic among key populations remains unknown in several countries due to persistent data gaps. The HIV response in Middle East and north Africa remains far below global targets for prevention, testing, and treatment. It is hindered by underfunding, poor surveillance, and stigma, all of which are compounded by widespread conflict and humanitarian crises, and most recently, the advent of COVID-19. Investment is needed to put the region on track towards the target of eliminating HIV/AIDS as a global health threat by 2030. Reaching this target will not be possible without tailoring the response to the needs of key populations, while addressing, to the extent possible, the complex structural and operational barriers to success.


Subject(s)
COVID-19 , HIV Infections , Sex Workers , Sexual and Gender Minorities , Africa, Northern/epidemiology , Female , HIV Infections/epidemiology , HIV Infections/prevention & control , Homosexuality, Male , Humans , Male , Middle East/epidemiology
4.
N Engl J Med ; 387(1): 21-34, 2022 07 07.
Article in English | MEDLINE | ID: covidwho-1890356

ABSTRACT

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.).


Subject(s)
2019-nCoV Vaccine mRNA-1273 , BNT162 Vaccine , COVID-19 , Immunity, Innate , Immunization , SARS-CoV-2 , 2019-nCoV Vaccine mRNA-1273/immunology , 2019-nCoV Vaccine mRNA-1273/therapeutic use , BNT162 Vaccine/immunology , BNT162 Vaccine/therapeutic use , COVID-19/immunology , COVID-19/prevention & control , COVID-19/virology , Case-Control Studies , Humans , Immunity, Innate/immunology , Immunization, Secondary , Recurrence , SARS-CoV-2/immunology , Vaccination
5.
Clin Infect Dis ; 2022 Apr 11.
Article in English | MEDLINE | ID: covidwho-1886383

ABSTRACT

BACKGROUND: There are limited data assessing COVID-19 disease severity in children/adolescents infected with the Omicron variant. METHODS: We identified children and adolescents <18 years with SARS-CoV-2 infection with Delta and propensity-score matched controls with Omicron variant infection from the National COVID-19 Database in Qatar. Primary outcome was disease severity, determined by hospital admission, admission to ICU, or mechanical ventilation within 14 days of diagnosis, or death within 28 days. RESULTS: Among 1,735 cases with Delta variant infection between June 1 and November 6, 2021 and 32 635 cases with Omicron variant infection between January 1 and January 15, 2022 who did not have prior infection and were not vaccinated, we identified 985 propensity-score matched pairs. Among Delta infected, 84.2% had mild, 15.7% had moderate, and 0.1% had severe/critical disease. Among Omicron infected, 97.8% had mild, 2.2% had moderate, and none had severe/critical disease (P < .001). Omicron variant infection (vs. Delta) was associated with significantly lower odds of moderate or severe/critical disease (adjusted odds ratio, 0.12; 95% CI 0.07-0.18). Those aged 6-11, and 12-<18 years had lower odds of developing moderate or severe/critical disease compared with those younger than six years (aOR, 95% CI 0.47; 0.33-0.66 for 6-11 year old; aOR 0.45, 95% CI 0.21-0.94 for 12-<18 years old). CONCLUSIONS: Omicron variant infection in children/adolescents is associated with less severe disease than Delta variant infection as measured by hospitalization rates and need for ICU care or mechanical ventilation. Those 6 to <18 years also have less severe disease than those <6 years old.

6.
J Travel Med ; 2022 May 27.
Article in English | MEDLINE | ID: covidwho-1873966

ABSTRACT

Compared to BA.1, BA.2 was associated with lower RT-qPCR cycle threshold (Ct) value-3.53 fewer cycles (95% CI: 3.46-3.60), signifying higher infectiousness. This may reflect higher viral load and/or longer duration of infection for BA.2. Natural immunity from previous infection and booster vaccination were associated with less infectious breakthrough infections.

7.
Nat Commun ; 13(1): 3082, 2022 06 02.
Article in English | MEDLINE | ID: covidwho-1873502

ABSTRACT

SARS-CoV-2 Omicron BA.1 and BA.2 subvariants are genetically divergent. We conducted a matched, test-negative, case-control study to estimate duration of protection of the second and third/booster doses of mRNA COVID-19 vaccines against BA.1 and BA.2 infections in Qatar. BNT162b2 effectiveness was highest at 46.6% (95% CI: 33.4-57.2%) against symptomatic BA.1 and at 51.7% (95% CI: 43.2-58.9%) against symptomatic BA.2 infections in the first three months after the second dose, but declined to ~10% or below thereafter. Effectiveness rebounded to 59.9% (95% CI: 51.2-67.0%) and 43.7% (95% CI: 36.5-50.0%), respectively, in the first month after the booster dose, before declining again. Effectiveness against COVID-19 hospitalization and death was 70-80% after the second dose and >90% after the booster dose. mRNA-1273 vaccine protection showed similar patterns. mRNA vaccines provide comparable, moderate, and short-lived protection against symptomatic BA.1 and BA.2 Omicron infections, but strong and durable protection against COVID-19 hospitalization and death.


Subject(s)
COVID-19 , SARS-CoV-2 , 2019-nCoV Vaccine mRNA-1273 , BNT162 Vaccine , COVID-19/epidemiology , COVID-19/prevention & control , COVID-19 Vaccines , Case-Control Studies , Humans , Qatar/epidemiology , SARS-CoV-2/genetics , Vaccines, Synthetic , mRNA Vaccines
8.
BMC Infect Dis ; 22(1): 458, 2022 May 13.
Article in English | MEDLINE | ID: covidwho-1846800

ABSTRACT

BACKGROUND: Prospective observational data show that infected persons with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remain polymerase chain reaction (PCR) positive for a prolonged duration, and that detectable antibodies develop slowly with time. We aimed to analyze how these effects can bias key epidemiological metrics used to track and monitor SARS-CoV-2 epidemics. METHODS: An age-structured mathematical model was constructed to simulate progression of SARS-CoV-2 epidemics in populations. PCR testing to diagnose infection and cross-sectional surveys to measure seroprevalence were also simulated. Analyses were conducted on simulated outcomes assuming a natural epidemic time course and an epidemic in presence of interventions. RESULTS: The prolonged PCR positivity biased the epidemiological measures. There was a lag of 10 days between the true epidemic peak and the actually-observed peak. Prior to epidemic peak, PCR positivity rate was twofold higher than that based only on current active infection, and half of those tested positive by PCR were in the prolonged PCR positivity stage after infection clearance. Post epidemic peak, PCR positivity rate poorly predicted true trend in active infection. Meanwhile, the prolonged PCR positivity did not appreciably bias estimation of the basic reproduction number R0. The time delay in development of detectable antibodies biased measured seroprevalence. The actually-observed seroprevalence substantially underestimated true prevalence of ever infection, with the underestimation being most pronounced around epidemic peak. CONCLUSIONS: Caution is warranted in interpreting PCR and serological testing data, and any drawn inferences need to factor the effects of the investigated biases for an accurate assessment of epidemic dynamics.


Subject(s)
COVID-19 , SARS-CoV-2 , Antibodies, Viral , Benchmarking , Bias , COVID-19/diagnosis , COVID-19/epidemiology , Cross-Sectional Studies , Humans , Polymerase Chain Reaction , SARS-CoV-2/genetics , Seroepidemiologic Studies
9.
EuropePMC; 2022.
Preprint in English | EuropePMC | ID: ppcovidwho-336237

ABSTRACT

Effectiveness of sotrovimab against severe, critical, or fatal COVID-19 was investigated in Qatar using a case-control study design at a time when BA.2 Omicron subvariant dominated incidence. Adjusted odds ratio of progression to severe, critical, or fatal COVID-19, comparing those sotrovimab-treated to those untreated, was 2.67-fold higher (95% CI: 0.60-11.91).

10.
EuropePMC; 2022.
Preprint in English | EuropePMC | ID: ppcovidwho-336165

ABSTRACT

A number of studies reported that influenza vaccination is associated with lower risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and/or coronavirus disease 2019 (COVID-19) morbidity and mortality. We conducted a matched, test-negative, case-control study to estimate effectiveness of influenza vaccination, using Abbott’s quadrivalent Influvac Tetra vaccine, against SARS-CoV-2 infection and against severe COVID-19. The study was implemented on a population of 30,774 healthcare workers (HCWs) in Qatar during the 2020 annual influenza vaccination campaign, between September 17, 2020 and December 31, 2020, before introduction of COVID-19 vaccination. The median age in the matched samples was 36 years (interquartile range (IQR), 32-44) for cases and 35 years (IQR, 32-42) for controls. The median duration between influenza vaccination and the PCR test was 43 days (IQR, 29-62). The estimated effectiveness of influenza vaccination against SARS-CoV-2 infection >14 days after receiving the vaccine was 29.7% (95% CI: 5.5-47.7%). The estimated effectiveness of influenza vaccination against any severe, critical, or fatal COVID-19 was 88.9% (95% CI: 4.1-98.7%). Sensitivity analyses confirmed main analysis results. Recent influenza vaccination is associated with an appreciable reduction in the risk of SARS-CoV-2 infection and COVID-19 severity.

11.
Epidemics ; 39: 100567, 2022 06.
Article in English | MEDLINE | ID: covidwho-1796867

ABSTRACT

Different COVID-19 treatment candidates are under development, and some are becoming available including two promising drugs from Merck and Pfizer. This study provides conceptual frameworks for the effects of three types of treatments, both therapeutic and prophylactic, and to investigate their population-level impact, to inform drug development, licensure, decision-making, and implementation. Different drug efficacies were assessed using an age-structured mathematical model describing SARS-CoV-2 transmission and disease progression, with application to the United States as an illustrative example. Severe and critical infection treatment reduces progression to COVID-19 severe and critical disease and death with small number of treatments needed to avert one disease or death. Post-exposure prophylaxis treatment had a large impact on flattening the epidemic curve, with large reductions in infection, disease, and death, but the impact was strongly age dependent. Pre-exposure prophylaxis treatment had the best impact and effectiveness, with immense reductions in infection, disease, and death, driven by the robust control of infection transmission. Effectiveness of both pre-exposure and post-exposure prophylaxis treatments was disproportionally larger when a larger segment of the population was targeted than a specific age group. Additional downstream potential effects of treatment, beyond the primary outcome, enhance the population-level impact of both treatments. COVID-19 treatments are an important modality in controlling SARS-CoV-2 disease burden. Different types of treatment act synergistically for a larger impact, for these treatments and vaccination.


Subject(s)
COVID-19 , Pre-Exposure Prophylaxis , COVID-19/drug therapy , COVID-19/epidemiology , Humans , SARS-CoV-2 , United States/epidemiology
12.
EuropePMC; 2022.
Preprint in English | EuropePMC | ID: ppcovidwho-330779

ABSTRACT

BACKGROUND Protection conferred by natural SARS-CoV-2 infection versus COVID-19 vaccination has not been investigated in rigorously controlled studies. We compared head-to-head protection conferred by natural infection to that from the BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna) vaccines in Qatar, between February 28, 2020 and March 6, 2022. METHODS Two national matched retrospective target-trial cohort studies were conducted to compare incidence of SARS-CoV-2 infection and COVID-19 hospitalization and death among those with a documented primary infection to incidence among those with a two-dose primary-series vaccination. Associations were estimated using Cox proportional-hazards regression models. RESULTS The overall adjusted hazard ratio (AHR) for infection was 0.46 (95% CI: 0.45-0.48) comparing those with a prior infection to those vaccinated with BNT162b2, and 0.51 (95% CI: 0.48-0.53) comparing those with a prior infection to those vaccinated with mRNA-1273. For BNT162b2, the AHR decreased gradually from 0.55 (95% CI: 0.46-0.65) in the fourth month after primary infection/vaccination to 0.31 (95% CI: 0.27-0.37) in the eighth month, while for mRNA-1273, it decreased from 0.80 (95% CI: 0.59-1.07) to 0.35 (95% CI: 0.29-0.41) over the same time period. During the Omicron wave, the AHR was ∼0.50 for BNT162b2 and ∼0.60 for mRNA-1273. The overall AHR for any severe, critical, or fatal COVID-19 (against all variants) was 0.32 (95% CI: 0.10-1.00) for BNT162b2, and 0.58 (95% CI: 0.14-2.43) for mRNA-1273. CONCLUSIONS Natural infection was associated with stronger and more durable protection against infection, regardless of the variant, than mRNA primary-series vaccination. Nonetheless, vaccination remains the safest and optimal tool of protection against infection and COVID-19 hospitalization and death.

13.
EuropePMC; 2022.
Preprint in English | EuropePMC | ID: ppcovidwho-330725

ABSTRACT

BACKGROUND: Protection offered by five different forms of immunity, combining natural and vaccine immunity, was investigated against SARS-CoV-2 Omicron symptomatic BA.1 infection, symptomatic BA.2 infection, BA.1 hospitalization and death, and BA.2 hospitalization and death, in Qatar, between December 23, 2021 and February 21, 2022. METHODS: Six national, matched, test-negative case-control studies were conducted to estimate effectiveness of BNT162b2 (Pfizer-BioNTech) vaccine, mRNA-1273 (Moderna) vaccine, natural immunity due to prior infection with pre-Omicron variants, and hybrid immunity from prior infection and vaccination. RESULTS: Effectiveness of only prior infection against symptomatic BA.2 infection was 46.1% (95% CI: 39.5-51.9%). Effectiveness of only two-dose BNT162b2 vaccination was negligible at -1.1% (95% CI: -7.1-4.6), but nearly all individuals had received their second dose several months earlier. Effectiveness of only three-dose BNT162b2 vaccination was 52.2% (95% CI: 48.1-55.9%). Effectiveness of hybrid immunity of prior infection and two-dose BNT162b2 vaccination was 55.1% (95% CI: 50.9-58.9%). Effectiveness of hybrid immunity of prior infection and three-dose BNT162b2 vaccination was 77.3% (95% CI: 72.4-81.4%). Meanwhile, prior infection, BNT162b2 vaccination, and hybrid immunity all showed strong effectiveness >70% against any severe, critical, or fatal COVID-19 due to BA.2 infection. Similar levels and patterns of effectiveness were observed for BA.1 and for the mRNA-1273 vaccine. CONCLUSIONS: There are no discernable differences in the effects of prior infection, vaccination, and hybrid immunity against BA.1 versus BA.2. Hybrid immunity resulting from prior infection and recent booster vaccination confers the strongest protection against either subvariant. Vaccination enhances protection of those with a prior infection.

14.
EuropePMC; 2022.
Preprint in English | EuropePMC | ID: ppcovidwho-330103

ABSTRACT

The SARS-CoV-2 Omicron (B.1.1.529) variant has two subvariants, BA.1 and BA.2, that are genetically quite divergent. We conducted a matched, test-negative, case-control study to estimate duration of protection of mRNA COVID-19 vaccines, after the second dose and after a third/booster dose, against BA.1 and BA.2 infections in Qatar’s population. BNT162b2 effectiveness against symptomatic BA.1 infection was highest at 46.6% (95% CI: 33.4-57.2%) in the first three months after the second dose, but then declined to ∼10% or below thereafter. Effectiveness rapidly rebounded to 59.9% (95% CI: 51.2-67.0%) in the first month after the booster dose, but then started to decline again. BNT162b2 effectiveness against symptomatic BA.2 infection was highest at 51.7% (95% CI: 43.2-58.9%) in the first three months after the second dose, but then declined to ∼10% or below thereafter. Effectiveness rapidly rebounded to 43.7% (95% CI: 36.5-50.0%) in the first month after the booster dose, but then declined again. Effectiveness against COVID-19 hospitalization and death was in the range of 70-80% any time after the second dose, and was greater than 90% after the booster dose. Similar patterns of protection were observed for the mRNA-1273 vaccine. mRNA vaccines provide only moderate and short-lived protection against symptomatic Omicron infections, with no discernable differences in protection against either the BA.1 or BA.2 subvariants. Vaccine protection against COVID-19 hospitalization and death is strong and durable after the second dose, but is more robust after a booster dose.

15.
EuropePMC; 2022.
Preprint in English | EuropePMC | ID: ppcovidwho-329824

ABSTRACT

BACKGROUND Qatar experienced a large SARS-CoV-2 Omicron (B.1.1.529) wave that started on December 19, 2021 and peaked in mid-January, 2022. We investigated effects of Omicron subvariant (BA.1 and BA.2), previous vaccination, and prior infection on infectiousness of Omicron infections, between December 23, 2021 and February 20, 2022. METHODS Univariable and multivariable regression analyses were conducted to estimate the association between the RT-qPCR cycle threshold (Ct) value of PCR tests (a proxy for SARS-CoV-2 infectiousness) and each of the Omicron subvariants, mRNA vaccination, prior infection, reason for RT-qPCR testing, calendar week of RT-qPCR testing (to account for phases of the rapidly evolving Omicron wave), and demographic factors. RESULTS Compared to BA.1, BA.2 was associated with 3.53 fewer cycles (95% CI: 3.46-3.60), signifying higher infectiousness. Ct value decreased with time since second and third vaccinations. Ct values were highest for those who received their boosters in the month preceding the RT-qPCR test—0.86 cycles (95% CI: 0.72-1.00) higher than for unvaccinated persons. Ct value was 1.30 (95% CI: 1.20-1.39) cycles higher for those with a prior infection compared to those without prior infection, signifying lower infectiousness. Ct value declined gradually with age. Ct value was lowest for those who were tested because of symptoms and was highest for those who were tested for travel-related purposes. Ct value was lowest during the exponential-growth phase of the Omicron wave and was highest after the wave peaked and was declining. CONCLUSIONS The BA.2 subvariant appears substantially more infectious than the BA.1 subvariant. This may reflect higher viral load and/or longer duration of infection, thereby explaining the rapid expansion of this subvariant in Qatar.

16.
N Engl J Med ; 386(19): 1804-1816, 2022 05 12.
Article in English | MEDLINE | ID: covidwho-1735349

ABSTRACT

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.).


Subject(s)
/immunology , COVID-19 , COVID-19/epidemiology , COVID-19/immunology , COVID-19/prevention & control , COVID-19 Vaccines , Cohort Studies , Humans , Immunization, Secondary , Immunogenicity, Vaccine , Qatar/epidemiology , RNA, Messenger , Retrospective Studies , SARS-CoV-2 , Vaccines, Synthetic
17.
Glob Epidemiol ; 3: 100068, 2021 Nov.
Article in English | MEDLINE | ID: covidwho-1729789

ABSTRACT

We aimed to estimate, albeit crudely and provisionally, national, regional, and global proportions of respective populations that have been infected with SARS-CoV-2 in the first year after the introduction of this virus into human circulation, and to assess infection morbidity and mortality rates, factoring both documented and undocumented infections. The estimates were generated by applying mathematical models to 159 countries and territories. The percentage of the world's population that has been infected as of 31 December 2020 was estimated at 12.56% (95% CI: 11.17-14.05%). It was lowest in the Western Pacific Region at 0.66% (95% CI: 0.59-0.75%) and highest in the Americas at 41.92% (95% CI: 37.95-46.09%). The global infection fatality rate was 10.73 (95% CI: 10.21-11.29) per 10,000 infections. Globally per 1000 infections, the infection acute-care bed hospitalization rate was 19.22 (95% CI: 18.73-19.51), the infection ICU bed hospitalization rate was 4.14 (95% CI: 4.10-4.18). If left unchecked with no vaccination and no other public health interventions, and assuming circulation of only wild-type variants and no variants of concern, the pandemic would eventually cause 8.18 million deaths (95% CI: 7.30-9.18), 163.67 million acute-care hospitalizations (95% CI: 148.12-179.51), and 33.01 million ICU hospitalizations (95% CI: 30.52-35.70), by the time the herd immunity threshold is reached at 60-70% infection exposure. The global population remained far below the herd immunity threshold by end of 2020. Global epidemiology reveals immense regional variation in infection exposure and morbidity and mortality rates.

18.
EuropePMC; 2022.
Preprint in English | EuropePMC | ID: ppcovidwho-329470

ABSTRACT

BACKGROUND The SARS-CoV-2 Omicron (B.1.1.529) variant has two main sub-lineages, BA.1 and BA.2 with significant genetic distance between them. This study investigated protection of infection with one sub-lineage against reinfection with the other sub-lineage in Qatar during a large BA.1 and BA.2 Omicron wave, from December 19, 2021 to February 21, 2022. METHODS Two national matched, retrospective cohort studies were conducted to estimate effectiveness of BA.1 infection against reinfection with BA.2 (N=20,197;BA.1-against-BA.2 study), and effectiveness of BA.2 infection against reinfection with BA.1 (N=100,925;BA.2-against-BA.1 study). Associations were estimated using Cox proportional-hazards regression models. RESULTS In the BA.1-against-BA.2 study, cumulative incidence of infection was estimated at 0.03% (95% CI: 0.01-0.07%) for the BA.1-infected cohort and at 0.62% (95% CI: 0.51-0.75%) for the uninfected-control cohort, 15 days after the start of follow-up. Effectiveness of BA.1 infection against reinfection with BA.2 was estimated at 94.9% (95% CI: 88.4-97.8%). In the BA.2-against-BA.1 study, cumulative incidence of infection was estimated at 0.03% (95% CI: 0.02-0.04%) for the BA.2-infected cohort and at 0.17% (95% CI: 0.15-0.21%) for the uninfected-control cohort, 15 days after the start of follow-up. Effectiveness of BA.2 infection against reinfection with BA.1 was estimated at 85.6% (95% CI: 77.4-90.9%). CONCLUSIONS Infection with an Omicron sub-lineage appears to induce strong, but not full protection against reinfection with the other sub-lineage, for at least several weeks after the initial infection.

19.
Lancet ; 399(10327): 771-773, 2022 02 26.
Article in English | MEDLINE | ID: covidwho-1707951
20.
EuropePMC;
Preprint in English | EuropePMC | ID: ppcovidwho-327514

ABSTRACT

BACKGROUND Qatar has been experiencing a large SARS-CoV-2 Omicron (B.1.1.529) wave that started on December 19, 2021. We assessed duration of protection of BNT162b2 (Pfizer-BioNTech) and mRNA-1273 (Moderna) COVID-19 vaccines after second dose and after third/booster dose against symptomatic Omicron infection and against COVID-19 hospitalization and death, between December 23, 2021 and February 2, 2022. METHODS Vaccine effectiveness was estimated using the test-negative, case-control study design, applying the same methodology used earlier to assess waning of BNT162b2 and mRNA-1273 effectiveness in the same population during earlier infection waves. RESULTS BNT162b2 effectiveness against symptomatic Omicron infection was highest at 61.9% (95% CI: 49.9-71.1%) in the first month after the second dose, but then gradually declined and was at 10% or less starting from the 5 th month after the second dose. After the booster, effectiveness rapidly rebounded to peak at about 55% between 2-5 weeks after the booster, but then started to decline again thereafter. Effectiveness against severe, critical, or fatal COVID-19 was maintained at >70% after the second dose and at >90% after the booster with no evidence for declining effectiveness over time. mRNA-1273 effectiveness against symptomatic Omicron infection was highest at 44.8% (95% CI: 16.0-63.8%) in the first three months after the second dose, before gradually declining to negligible levels thereafter. After the booster, effectiveness rapidly rebounded to peak at about 55% between 2-5 weeks after the booster, but then declined again thereafter. Effectiveness against severe, critical, or fatal COVID-19 was high at >60% after the second dose and at >80% after the booster, but the confidence intervals were wide owing to the small number of cases. CONCLUSIONS BNT162b2 and mRNA-1273 vaccines show a similar level and pattern of protection against symptomatic Omicron infection. Protection against Omicron is lower than that against Alpha, Beta, and Delta variants, and wanes more rapidly than against earlier variants after the second and booster doses. Meanwhile, protection against hospitalization and death appears robust and durable after both the second and booster doses.

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