Protection of natural infection against reinfection with SARS-CoV-2 JN.1 variant

Overall effectiveness of infection in preventing reinfection with SARS-CoV-2 JN.1 variant was estimated at 1.8% (95% CI: -9.3-12.6%), and demonstrated rapid decline over time since the previous infection, decreasing from 82.4% (95% CI: 40.9 to 94.7%) within 3 to less than 6 months, to a negligible level after one year.

Bivalent mRNA-1273.214 vaccine effectiveness against SARS-CoV-2 omicron XBB* infections

Effectiveness of the 50-μg mRNA-1273.214 bivalent vaccine against SARS-CoV-2 infection was modest at 25% in a matched, retrospective, cohort study in Qatar comparing infection incidence in the bivalent cohort to that in the national no-recent-vaccination resident cohort. XBB* immune evasion, immune imprinting effects, or both, may explain findings.

Covid-19 Vaccine Protection among Children and Adolescents in Qatar

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.).

Effects of Previous Infection and Vaccination on Symptomatic Omicron Infections

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.).

COVID-19 disease severity in persons infected with the Omicron variant compared with the Delta variant in Qatar

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.

Duration of COVID-19 mRNA Vaccine Effectiveness against Severe Disease

Waning immunity following administration of mRNA-based COVID-19 vaccines remains a concern for many health systems. We undertook a study to determine if recent reports of waning for severe disease could have been attributed to design-related bias by conducting a study only among those detected with a first SARS-CoV-2 infection. We used a matched case-control study design with the study base being all individuals with first infection with SARS-CoV-2 reported in the State of Qatar between 1 January 2021 and 20 February 2022. Cases were those detected with first SARS-CoV-2 infection requiring intensive care (hard outcome), while controls were those detected with first SARS-CoV-2 infection who recovered without the need for intensive care. Cases and controls were matched in a 1:30 ratio for the calendar month of infection and the comorbidity category. Duration and magnitude of conditional vaccine effectiveness against requiring intensive care and the number needed to vaccinate (NNV) to prevent one more case of COVID-19 requiring intensive care was estimated for the mRNA (BNT162b2/mRNA-1273) vaccines. Conditional vaccine effectiveness against requiring intensive care was 59% (95% confidence interval (CI), 50 to 76) between the first and second dose, and strengthened to 89% (95% CI, 85 to 92) between the second dose and 4 months post the second dose in persons who received a primary course of the vaccine. There was no waning of vaccine effectiveness in the period from 4 to 6, 6 to 9, and 9 to 12 months after the second dose. This study demonstrates that, contrary to mainstream reports using hierarchical measures of effectiveness, conditional vaccine effectiveness against requiring intensive care remains robust till at least 12 months after the second dose of mRNA-based vaccines.

Effect of mRNA Vaccine Boosters against SARS-CoV-2 Omicron Infection in Qatar

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.).

COVID-19 Disease Severity in Children Infected with the Omicron Variant

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.

Severity of Illness in Persons Infected With the SARS-CoV-2 Delta Variant vs Beta Variant in Qatar

IMPORTANCE

The Delta variant is now the predominant circulating SARS-CoV-2 strain worldwide. Severity of illness in persons infected with the SARS-CoV-2 Delta variant compared with the Beta variant is not known.

OBJECTIVE

To directly compare clinical outcomes in persons infected with the SARS-CoV-2 Delta variant vs those infected with the Beta variant in Qatar.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study used data from the national COVID-19 database in Qatar, which includes information on all individuals who were ever tested for SARS-CoV-2 using a reverse transcriptase-polymerase chain reaction test and all individuals who received any SARS-CoV-2 vaccine in Qatar. Among persons with confirmed SARS-CoV-2 infection between March 22 and July 7, 2021, those infected with the Delta variant were identified and were propensity score matched with control individuals infected with the Beta variant. The variants were ascertained by variant genotyping of the positive samples.

EXPOSURES

SARS-CoV-2 infection with the Delta or Beta variant.

MAIN OUTCOMES AND MEASURES

The main outcomes were admission to the hospital, admission to the intensive care unit, use of supplemental oxygen, use of high-flow oxygen, receipt of mechanical ventilation, or death among those infected with the Delta or Beta variant overall and stratified by vaccination status.

RESULTS

Among 1427 persons infected with the Delta variant (252 [55.9%] male; median age, 34 years [IQR, 17-43 years]) and 5353 persons infected with the Beta variant (233 [51.7%] male; median age, 34 years [IQR, 17-45 years]), 451 propensity score-matched pairs were identified. Persons infected with the Delta variant were more likely to be hospitalized (27.3% [95% CI, 23.2%-31.6%] vs 20.0% [95% CI, 16.4-24.0]; P = .01) or to have mild-moderate or severe-critical disease outcomes (27.9% [95% CI, 23.8%-32.3%] vs 20.2% [95% CI, 16.6%-24.2%]; P = .01) compared with persons infected with the Beta variant. Infection with the Delta variant was independently associated with higher odds of experiencing any adverse outcome (adjusted odds ratio [aOR], 2.53; 95% CI, 1.72-3.72). Compared with being unvaccinated, being vaccinated with a second dose more than 3 months before infection was associated with lower odds of any adverse outcome among persons infected with the Delta variant (aOR, 0.11; 95% CI, 0.04-0.26) and among those infected with the Beta variant (aOR, 0.22; 95% CI, 0.05-0.98). Protection was similar among those who received a second vaccine dose less than 3 months before infection, but having received only a single dose was not associated with a lower odds of any severe outcome among those infected with the Delta variant (aOR, 1.12; 95% CI, 0.41-3.06) or those infected with the Beta variant (aOR, 0.74; 95% CI, 0.20-2.72).

CONCLUSIONS AND RELEVANCE

In this cohort study of persons with COVID-19 in Qatar, infection with the SARS-CoV-2 Delta variant was associated with more severe disease than was infection with the Beta variant. Being unvaccinated was associated with greater odds of severe-critical disease.

Waning of BNT162b2 Vaccine Protection against SARS-CoV-2 Infection in Qatar

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.).

SARS-CoV-2 vaccine effectiveness in preventing confirmed infection in pregnant women

BackgroundSARS-CoV-2 infection in pregnancy is associated with a higher risk of pregnancy-related complications and neonatal respiratory distress and hospitalization. Effectiveness of SARS-CoV-2 vaccines in pregnant women is not known.MethodsAll women with confirmed pregnancy who presented to the national referral hospital in Qatar between December 20, 2020, and May 30, 2021, with at least 1 SARS-CoV-2 test and not testing prior to pregnancy were included. We determined the vaccine effectiveness of mRNA vaccines in preventing confirmed SARS-CoV-2 infection during pregnancy using both cohort and test-negative case-control designs. Analyses were adjusted for age group, nationality, and gestational age.ResultsAmong 4534 pregnant women, there were 407 vaccinated and 407 unvaccinated women in the matched cohort analysis. Vaccine effectiveness was 87.6% (95%CI 44.1%-97.2%) at least 14 days after the second dose. There were 386 test-positive and 834 matched women in the test-negative case control analysis. Vaccine effectiveness was 86.8% (95%CI 47.5%-98.5%) at least 14 days after the second dose. Adjustment for age, nationality, and gestational age yielded similar results for both designs. In the test-negative analysis, vaccine effectiveness at least 14 days after the first dose but before the second dose was 40.8% (95% CI 0.0%-80.4%). Of the 386 test-positive pregnant women, 74 cases were Alpha variant, 163 cases were Beta variant, and 156 cases were variants of unknown status. There were 9 severe or critical disease cases and no deaths in the test-positive pregnant women, all of whom were unvaccinated.ConclusionThe mRNA vaccines provide a high level of protection against documented SARS-CoV-2 infection, which supports the inclusion of pregnant women in vaccination campaigns.FUNDINGHamad Medical Corporation, Weill Cornell Medicine Qatar, and the Ministry of Public Health Qatar.

Risk factors for breakthrough SARS-CoV-2 infection in vaccinated healthcare workers

Background and objective

The risk factors for breakthrough infections among healthcare workers (HCW) after completion of a full course of vaccination are poorly understood. Our objective was to determine the risk factors for breakthrough SARS-CoV-2 infection among HCWs at a national healthcare system in Qatar.

Methods

We identified all HCWs at Hamad Medical Corporation in Qatar between December 20, 2020 and May 18, 2021 with confirmed SARS-CoV-2 RT-PCR infection >14 days after the second vaccine dose. For each case thus identified, we identified one control with a negative test after December 20, 2020, matched on age, sex, nationality, job family and date of SARS-CoV-2 testing. We excluded those with a prior positive test and temporary workers. We used Cox regression analysis to determine factors associated with breakthrough infection.

Results

Among 22,247 fully vaccinated HCW, we identified 164 HCW who had breakthrough infection and matched them to 164 controls to determine the factors associated with SARS-CoV-2 breakthrough infection. In the breakthrough infection group the nursing and midwifery job family constituted the largest group, spouse was identified as the most common positive contact followed by a patient. Exposure to a confirmed case, presence of symptoms and all other job families except Allied Health Professionals when compared with nursing and Midwifery staff independently predicted infection.

Conclusion

Presence of symptoms and contact with a confirmed case are major risk factors for breakthrough SARS-CoV-2 infection after vaccination, and these groups should be prioritized for screening even after full vaccination.