scholarly journals Single-dose mRNA vaccine effectiveness against SARS-CoV-2, including P.1 and B.1.1.7 variants: a test-negative design in adults 70 years and older in British Columbia, Canada

2021 ◽  
Author(s):  
Danuta M Skowronski ◽  
Solmaz Setayeshgar ◽  
Macy Zou ◽  
Natalie Prystajecky ◽  
John R Tyson ◽  
...  
Keyword(s):  
British Columbia ◽  
Single Dose ◽  
Vaccine Effectiveness ◽  
Community Dwelling ◽  
Rt Pcr ◽  
Vaccine Protection ◽  
Post Vaccination ◽  
Randomized Controlled ◽  
Specimen Collection ◽  
Negative Controls

Introduction: Randomized-controlled trials of mRNA vaccine protection against SARS-CoV-2 included relatively few elderly participants. We assess singe-dose mRNA vaccine effectiveness (VE) in adults ≥70-years-old in British Columbia (BC), Canada where the second dose was deferred by up to 16 weeks and where a spring 2021 wave uniquely included co-dominant circulation of B.1.1.7 and P.1 variants of concern (VOC). Methods: Analyses included community-dwelling adults ≥70-years-old with specimen collection between April 4 (epidemiological week 14) and May 1 (week 17). Adjusted VE was estimated by test-negative design through provincial laboratory and immunization data linkage. Cases were RT-PCR test-positive for SARS-CoV-2 and controls were test-negative. Vaccine status was defined by receipt of a single-dose ≥21 days before specimen collection, but a range of intervals was assessed. In variant-specific analyses, test-positive cases were restricted to those genetically-characterized as B.1.1.7, P.1 or non-VOC. Results: VE analyses included 16,993 specimens: 1,226 (7.2%) test-positive cases and 15,767 test-negative controls. Of 1,131 (92%) viruses genetically categorized, 509 (45%), 314 (28%) and 276 (24%) were B.1.1.7, P.1 and non-VOC lineages, respectively. VE was negligible at 14% (95% CI 0-26) during the period 0-13 days post-vaccination but increased from 43% (95% CI 30-53) at 14-20 days to 75% (95% CI 63-83) at 35-41 days post-vaccination. VE at ≥21 days was 65% (95% CI 58-71) overall: 72% (95% CI 58-81), 67% (95% CI 57-75) and 61% (95% CI 45-72) for non-VOC, B.1.1.7 and P.1, respectively. Conclusions: A single dose of mRNA vaccine reduced the risk of SARS-CoV-2 in adults ≥70-years-old by about two-thirds, with protection only minimally reduced against B.1.1.7 and P.1 variants. Substantial single-dose protection in older adults reinforces the option to defer the second dose when vaccine supply is scarce and broader first-dose coverage is needed.

scholarly journals Comparative single-dose mRNA and ChAdOx1 vaccine effectiveness against SARS-CoV-2, including early variants of concern: a test-negative design, British Columbia, Canada

2021 ◽  
Author(s):  
Danuta M Skowronski ◽  
Solmaz Setayeshgar ◽  
Macy Zou ◽  
Natalie Prystajecky ◽  
John R Tyson ◽  
...  
Keyword(s):  
British Columbia ◽  
Single Dose ◽  
Genetic Characterization ◽  
Infection Risk ◽  
Vaccine Effectiveness ◽  
Rt Pcr ◽  
Randomized Controlled ◽  
Specimen Collection ◽  
Dose Vaccine

Introduction: In randomized controlled trials, single-dose efficacy against SARS-CoV-2 illness exceeded 90% for mRNA vaccines (BNT162b2 and mRNA-1273), and 75% for ChAdOx1. In British Columbia (BC), Canada second doses were deferred up to 16 weeks and ChAdOx1 was only initially recommended for adults 55 years of age and older. We compared single-dose vaccine effectiveness (VE) during the spring 2021 wave in BC when Alpha and Gamma variants of concern (VOC) predominated. Methods: VE was estimated against infection and hospitalization by test-negative design: cases were RT-PCR test-positive for SARS-CoV-2 and controls were test-negative. Adults 50-69 years old with specimen collection between April 4 and May 22 (weeks 14-20) were included. Variant-specific VE was estimated between weeks 17-20 when genetic characterization of all case viruses was performed, primarily through whole genome sequencing. Results: VE analyses included 7,116 (10%) cases and 60,958 controls. Three-quarters of vaccinated participants received mRNA vaccine (60% BNT162b2, 15% mRNA-1273) and 25% received ChAdOx1. Half of genetically characterized viruses were Alpha, with 38% Gamma, 4% Delta and 8% non-VOCs. Single-dose VE against any infection was 75% (95%CI: 72-78) for BNT162b2, 82% (95%CI: 76-87) for mRNA-1273 and 61% (95%CI: 54-66) for ChAdOx1. VE against hospitalization was 83% (95%CI: 76-89), 85% (95%CI: 63-94) and 96% (95%CI: 86-99), respectively. VE against Alpha vs. Gamma infections did not differ among mRNA (78%;95%CI: 73-82 and 80%;95%CI: 74-85) or ChAdOx1 (66%;95%CI: 57-74 and 60%;95%CI: 48-69) recipients. Conclusions: A single dose of mRNA vaccine reduced the SARS-CoV-2 infection risk by at least 75%, including infections due to early VOC. Although effectiveness of a single dose of ChAdOx1 was lower at 60% against infection, just one dose of any vaccine reduced the hospitalization risk by more than 80%. In the context of constrained vaccine supplies, these findings have implications for global vaccine deployment to reduce the overall burden of infections and hospitalizations due to SARS-CoV-2.

scholarly journals Single-dose mRNA vaccine effectiveness against SARS-CoV-2 in healthcare workers extending 16 weeks post-vaccination: a test-negative design from Quebec, Canada

2021 ◽  
Author(s):  
Sara Carazo ◽  
Denis Talbot ◽  
Nicole Boulianne ◽  
Marc Brisson ◽  
Rodica Gilca ◽  
...  
Keyword(s):  
Single Dose ◽  
Healthcare Workers ◽  
Conditional Logistic Regression ◽  
Vaccine Dose ◽  
Vaccine Effectiveness ◽  
Primary Analysis ◽  
Post Vaccination ◽  
Illness Onset ◽  
Outcome Severity ◽  
Specimen Collection

Abstract Introduction In Canada, first and second doses of mRNA vaccines against SARS-CoV-2 were uniquely spaced 16 weeks apart, but the duration of single-dose protection remains uncertain. We estimated one- and two-dose mRNA vaccine effectiveness (VE) among healthcare workers (HCWs) in Quebec, Canada including protection against varying outcome severity, variants of concern (VOC), and the stability of single-dose protection out to 16 weeks post-vaccination. Methods A test-negative design compared vaccination among SARS-CoV-2 test-positive and weekly-matched (10:1), randomly-sampled, test-negative HCWs using linked surveillance and immunization databases. Vaccine status was defined by one dose ≥14 days or two doses ≥7 days before illness onset or specimen collection. Adjusted VE was estimated by conditional logistic regression. Results Primary analysis included 5,316 cases and 53,160 controls. Single-dose VE was 70% (95%CI: 68-73) against SARS-CoV-2 infection, 73% (95%CI: 71-75) against COVID-19 illness and 97% (95%CI: 92-99) against associated hospitalization. Two-dose VE was 86% (95%CI: 81-90) and 93% (95%CI: 89-95), respectively, with no associated hospitalizations. VE was higher for non-VOC than VOC (73% Alpha) among single-dose (77%, 95%CI: 73-81 versus 63%, 95%CI: 57-67) but not two-dose recipients (87%, 95%CI: 57-96 versus 94%, 95%CI: 89-96). Across 16 weeks, no decline in single-dose VE was observed with appropriate stratification based upon prioritized vaccination determined by higher versus lower likelihood of direct patient contact. Conclusion One mRNA vaccine dose provided substantial and sustained protection to HCWs extending at least four months post-vaccination. In circumstances of vaccine shortage, delaying the second dose may be a pertinent public health strategy to consider.

scholarly journals Two-dose SARS-CoV-2 vaccine effectiveness with mixed schedules and extended dosing intervals: test-negative design studies from British Columbia and Quebec, Canada

2021 ◽  
Author(s):  
Danuta M Skowronski ◽  
Solmaz Setayeshgar ◽  
Yossi Febriani ◽  
Manale Ouakki ◽  
Macy Zou ◽  
...  
Keyword(s):  
British Columbia ◽  
Vaccine Effectiveness ◽  
Community Dwelling ◽  
Design Studies ◽  
Post Vaccination ◽  
Equity And Access ◽  
Vaccine Type ◽  
Dosing Intervals ◽  
Global Health Equity ◽  
Dose Vaccine

Background The Canadian COVID-19 immunization strategy deferred second doses and allowed mixed schedules. We compared two-dose vaccine effectiveness (VE) by vaccine type (mRNA and/or ChAdOx1), interval between doses, and time since second dose in two of Canada's larger provinces. Methods Two-dose VE against infections and hospitalizations due to SARS-CoV-2, including variants of concern, was assessed between May 30 and October 2, 2021 using test-negative designs separately conducted among community-dwelling adults ≥18-years-old in British Columbia (BC) and Quebec, Canada. Findings In both provinces, two doses of homologous or heterologous SARS-CoV-2 vaccines were associated with ~95% reduction in the risk of hospitalization. VE exceeded 90% against SARS-CoV-2 infection when at least one dose was an mRNA vaccine, but was lower at ~70% when both doses were ChAdOx1. Estimates were similar by age group (including adults ≥70-years-old) and for Delta-variant outcomes. VE was significantly higher against both infection and hospitalization with longer 7-8-week vs. manufacturer-specified 3-4-week interval between doses. Two-dose mRNA VE was maintained against hospitalization for the 5-7-month monitoring period and while showing some decline against infection, remained ≥80%. Interpretation Two doses of mRNA and/or ChAdOx1 vaccines gave excellent protection against hospitalization, with no sign of decline by 5-7 months post-vaccination. A 7-8-week interval between doses improved VE and may be optimal in most circumstances. Findings indicate prolonged two-dose protection and support the use of mixed schedules and longer intervals between doses, with global health, equity and access implications in the context of recent third-dose proposals.

scholarly journals Single-dose mRNA vaccine effectiveness against SARS-CoV-2 in healthcare workers extending 16 weeks post-vaccination: a test-negative design from Quebec, Canada

2021 ◽  
Author(s):  
Sara Carazo ◽  
Denis Talbot ◽  
Nicole Boulianne ◽  
Marc Brisson ◽  
Rodica Gilca ◽  
...  
Keyword(s):  
Single Dose ◽  
Healthcare Workers ◽  
Conditional Logistic Regression ◽  
Vaccine Dose ◽  
Vaccine Effectiveness ◽  
Primary Analysis ◽  
Post Vaccination ◽  
Illness Onset ◽  
Outcome Severity ◽  
Specimen Collection

Introduction: In Canada, first and second doses of mRNA vaccines against SARS-CoV-2 were uniquely spaced 16 weeks apart, but the duration of single-dose protection remains uncertain. We estimated one- and two-dose mRNA vaccine effectiveness (VE) among healthcare workers (HCWs) in Quebec, Canada including protection against varying outcome severity, variants of concern (VOC), and the stability of single-dose protection out to 16 weeks post-vaccination. Methods: A test-negative design compared vaccination among SARS-CoV-2 test-positive and weekly-matched (10:1), randomly-sampled, test-negative HCWs using linked surveillance and immunization databases. Vaccine status was defined by one dose ≥14 days or two doses ≥7 days before illness onset or specimen collection. Adjusted VE was estimated by conditional logistic regression. Results: Primary analysis included 5,316 cases and 53,160 controls. Single-dose VE was 70% (95%CI: 68-73) against SARS-CoV-2 infection, 73% (95%CI: 71-75) against COVID-19 illness and 97% (95%CI: 92-99) against associated hospitalization. Two-dose VE was 86% (95%CI: 81-90) and 93% (95%CI: 89-95), respectively, with no associated hospitalizations. VE was higher for non-VOC than VOC (73% Alpha) among single-dose (77%, 95%CI: 73-81 versus 63%, 95%CI: 57-67) but not two-dose recipients (87%, 95%CI: 57-96 versus 94%, 95%CI: 89-96). Across 16 weeks, no decline in single-dose VE was observed with appropriate stratification based upon prioritized vaccination determined by higher versus lower likelihood of direct patient contact. Conclusion: One mRNA vaccine dose provided substantial and sustained protection to HCWs extending at least four months post-vaccination. In circumstances of vaccine shortage, delaying the second dose may be a pertinent public health strategy to consider.

scholarly journals Outbreak of SARS-CoV-2 in a prison: Low effectiveness of a single dose of the adenovirus vector ChAdOx1 vaccine in recently vaccinated inmates

2021 ◽  
Author(s):  
A Marco ◽  
N Teixidó ◽  
RA Guerrero ◽  
L Puig ◽  
X Rué ◽  
...  
Keyword(s):  
Single Dose ◽  
Observational Study ◽  
Preventive Measures ◽  
Adenovirus Vector ◽  
Vaccine Effectiveness ◽  
Infection Rates ◽  
Rt Pcr ◽  
Post Vaccination

AbstractIntroductionTo analyse the effectiveness of a dose of adenovirus vector ChAdOx1 vaccine (AVChOx1) in an outbreak of SARS-CoV-2 detected in a prison.MethodsObservational study carried out at Brians-1 Prison, Barcelona. After detecting a case of infection, rt-PCR was administered to all prisoners (some of whom had been vaccinated 21-23 days previously with a dose of AVChOx1) and to staff. Infection rates in vaccinated and unvaccinated populations were calculated, as was vaccine effectiveness.ResultsOne hundred and eighty-four asymptomatic prisoners (50.3% vaccinated) and 33 staff were screened. Forty-eight (25.9%) infections by the SCV-B.1.17 variant were recorded in prisoners and none in staff. Infection rates were higher in younger prisoners, immigrants, and those admitted ≥7 days previously. In all, 22.6% of vaccinated subjects were infected vs. 29.3% of unvaccinated. Vaccine effectiveness was 23%. Only 6.2 cases would have been prevented by vaccinating the unvaccinated individuals. At seven days, the rt-PCR was negative in 46.2% of vaccinated subjects vs. 13.6% of unvaccinated (p = 0.02).DiscussionIn a prison outbreak, a dose of AVChAdOx1 administered 21-23 days earlier did not significantly prevent the occurrence of infections, but did reduce the duration of rt-PCR positivity. Maintaining post-vaccination preventive measures is essential.

scholarly journals Effectiveness of BNT162b2 and mRNA-1273 covid-19 vaccines against symptomatic SARS-CoV-2 infection and severe covid-19 outcomes in Ontario, Canada: test negative design study

BMJ ◽  
2021 ◽  
pp. n1943 ◽  
Author(s):  
Hannah Chung ◽  
Siyi He ◽  
Sharifa Nasreen ◽  
Maria E Sundaram ◽  
Sarah A Buchan ◽  
...  
Keyword(s):  
Hospital Admission ◽  
Clinical Characteristics ◽  
Hospital Admissions ◽  
Vaccine Effectiveness ◽  
Community Dwelling ◽  
Rt Pcr ◽  
Chain Reaction ◽  
Design Study ◽  
Symptomatic Infection ◽  
Polymerase Chain

AbstractObjectiveTo estimate the effectiveness of mRNA covid-19 vaccines against symptomatic infection and severe outcomes (hospital admission or death).DesignTest negative design study.SettingOntario, Canada between 14 December 2020 and 19 April 2021.Participants324 033 community dwelling people aged ≥16 years who had symptoms of covid-19 and were tested for SARS-CoV-2.InterventionsBNT162b2 (Pfizer-BioNTech) or mRNA-1273 (Moderna) vaccine.Main outcome measuresLaboratory confirmed SARS-CoV-2 by reverse transcription polymerase chain reaction (RT-PCR) and hospital admissions and deaths associated with SARS-CoV-2 infection. Multivariable logistic regression was adjusted for personal and clinical characteristics associated with SARS-CoV-2 and vaccine receipt to estimate vaccine effectiveness against symptomatic infection and severe outcomes.ResultsOf 324 033 people with symptoms, 53 270 (16.4%) were positive for SARS-CoV-2 and 21 272 (6.6%) received at least one dose of vaccine. Among participants who tested positive, 2479 (4.7%) were admitted to hospital or died. Vaccine effectiveness against symptomatic infection observed ≥14 days after one dose was 60% (95% confidence interval 57% to 64%), increasing from 48% (41% to 54%) at 14-20 days after one dose to 71% (63% to 78%) at 35-41 days. Vaccine effectiveness observed ≥7 days after two doses was 91% (89% to 93%). Vaccine effectiveness against hospital admission or death observed ≥14 days after one dose was 70% (60% to 77%), increasing from 62% (44% to 75%) at 14-20 days to 91% (73% to 97%) at ≥35 days, whereas vaccine effectiveness observed ≥7 days after two doses was 98% (88% to 100%). For adults aged ≥70 years, vaccine effectiveness estimates were observed to be lower for intervals shortly after one dose but were comparable to those for younger people for all intervals after 28 days. After two doses, high vaccine effectiveness was observed against variants with the E484K mutation.ConclusionsTwo doses of mRNA covid-19 vaccines were observed to be highly effective against symptomatic infection and severe outcomes. Vaccine effectiveness of one dose was observed to be lower, particularly for older adults shortly after the first dose.

scholarly journals Vaccine effectiveness of Ad26.COV2.S against symptomatic COVID-19 and clinical outcomes in Brazil: a test-negative study design

2021 ◽  
Author(s):  
Otavio T Ranzani ◽  
Rogério dos Santos Leite ◽  
Larissa Domingues Castilho ◽  
Crhistinne Cavalheiro Maymone Gonçalves ◽  
Geraldo Resende ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Single Dose ◽  
Clinical Outcomes ◽  
Study Design ◽  
Vaccine Effectiveness ◽  
Rt Pcr ◽  
Mato Grosso ◽  
Negative Study ◽  
The Mean ◽  
Mato Grosso Do Sul

We used a test-negative design to estimate the vaccine effectiveness of Ad26.COV2.S (Janssen) against symptomatic COVID-19 and clinical outcomes in Mato-Grosso do Sul, Brazil. We analyzed 11,817 RT-PCR tests. The mean age was 37 (SD=17) years, 2,308 (20%) of individuals more or equal than 50 years and almost two-thirds of the population was Brown/Pardo. Adjusted effectiveness against symptomatic COVID-19 after 28 days of the single dose was 50.9% (95% CI, 35.5-63.0). Adjusted effectiveness against clinical outcomes was 72.9% (95% CI, 35.1-91.1) for hospitalization, 92.5% (95% CI, 54.9-99.6) for ICU admission, 88.7% (95% CI, 17.9-99.5) for mechanical ventilation and 90.5% (95% CI, 31.5-99.6) for death. Despite lacking precision on some estimates, a single dose of Ad26.COV2.S vaccine continues to protect specially for severe forms of COVID-19 in the context of new variants.

scholarly journals Effectiveness of BNT162b2 and mRNA-1273 COVID-19 vaccines against symptomatic SARS-CoV-2 infection and severe COVID-19 outcomes in Ontario, Canada

2021 ◽  
Author(s):  
Hannah Chung ◽  
Siyi He ◽  
Sharifa Nasreen ◽  
Maria Sundaram ◽  
Sarah A Buchan ◽  
...  
Keyword(s):  
Older Adults ◽  
Logistic Regression ◽  
Single Dose ◽  
Outcome Measures ◽  
Vaccine Dose ◽  
Community Dwelling ◽  
Administrative Databases ◽  
Rt Pcr ◽  
Symptomatic Infection ◽  
Younger Adults

Objectives: To estimate the effectiveness of one and two doses of mRNA COVID-19 vaccines against symptomatic infection and severe outcomes. Design: Using a test-negative design study and linked laboratory, vaccination, and health administrative databases, we estimated adjusted vaccine effectiveness (aVE) against symptomatic infection and severe outcomes (hospitalization or death) using multivariable logistic regression. Setting: Ontario, Canada between 14 December 2020 and 19 April 2021. Participants: Community-dwelling adults aged ≥16 years who were tested for SARS-CoV-2 and had COVID-19 symptoms. Interventions: Pfizer-BioNTech's BNT162b2 or Moderna's mRNA-1273 vaccine. Main outcome measures: Laboratory-confirmed SARS-CoV-2 identified by RT-PCR; hospitalization or death associated with SARS-CoV-2 infection. Results: Among 324,033 symptomatic individuals, 53,270 (16.4%) were positive for SARS-CoV-2 and 21,272 (6.6%) received 1 or more vaccine dose. Among test-positive cases, 2,479 (4.7%) had a severe outcome. aVE against symptomatic infection 14 days or more after receiving only 1 dose was 60% (95%CI, 57 to 64%), increasing from 48% (95%CI, 41 to 54%) at 14-20 days after the first dose to 71% (95%CI, 63 to 78%) at 35-41 days. aVE 7 days or more after receiving 2 doses was 91% (95%CI, 89 to 93%). Against severe outcomes, aVE 14 days or more after receiving 1 dose was 70% (95%CI, 60 to 77%), increasing from 62% (95%CI, 44 to 75%) at 14-20 days to 91% (95%CI, 73 to 97%) at 35 days or more, whereas aVE 7 days or more after receiving 2 doses was 98% (95%CI, 88 to 100%). For adults aged 70 years and older, aVE estimates were lower after receiving 1 dose, but were comparable to younger adults after 28 days. After 2 doses, we observed high aVE against E484K-positive variants. Conclusions: Two doses of BNT162b2 and mRNA-1273 vaccines are highly effective against both symptomatic infection and severe outcomes. Effectiveness is lower after only a single dose, particularly for older adults shortly after the first dose.

scholarly journals Comparison of influenza vaccine effectiveness in preventing outpatient and inpatient influenza cases in older adults, northern Spain, 2010/11 to 2015/16

2018 ◽  
Vol 23 (2) ◽  
Author(s):  
Jesús Castilla ◽  
Iván Martínez-Baz ◽  
Ana Navascués ◽  
Itziar Casado ◽  
Aitziber Aguinaga ◽  
...  
Keyword(s):  
Older Adults ◽  
Influenza Vaccine ◽  
Influenza A ◽  
Healthcare Setting ◽  
Vaccine Effectiveness ◽  
Community Dwelling ◽  
Influenza B ◽  
Northern Spain ◽  
Vaccine Failure ◽  
Negative Controls

Introduction We compared trivalent inactivated influenza vaccine effectiveness (VE) in preventing outpatient and inpatient influenza cases in Navarre, Spain. Methods: During seasons 2010/11 to 2015/16, community-dwelling patients with influenza-like illness aged 50 years or older were tested for influenza when attended by sentinel general practitioners or admitted to hospitals. The test–negative design was used to estimate and compare the VE by healthcare setting. Results: We compared 1,242 laboratory-confirmed influenza cases (557 outpatient and 685 inpatient cases) and 1,641 test-negative controls. Influenza VE was 34% (95% confidence interval (CI): 6 to 54) in outpatients and 32% (95% CI: 15 to 45) in inpatients. VE in outpatients and inpatients was, respectively, 41% (95% CI: –1 to 65) and 36% (95% CI: 12 to 53) against A(H1N1)pdm09, 5% (95% CI: –58 to 43) and 22% (95% CI: –9 to 44) against A(H3N2), and 49% (95% CI, 6 to 73) and 37% (95% CI: 2 to 59) against influenza B. Trivalent inactivated influenza vaccine was not associated with a different probability of hospitalisation among influenza cases, apart from a 54% (95% CI: 10 to 76) reduction in hospitalisation of influenza A(H3N2) cases. Conclusions: On average, influenza VE was moderate and similar in preventing outpatient and inpatient influenza cases over six influenza seasons in patients above 50 years of age. In some instances of low VE, vaccination may still reduce the risk of hospitalisation in older adults with vaccine failure.

scholarly journals Using routinely collected laboratory and health administrative data to assess influenza vaccine effectiveness: introducing the Flu and Other Respiratory Viruses Research (FOREVER) Cohort

2018 ◽  
Vol 3 (4) ◽  
Author(s):  
Jeff Kwong ◽  
Sarah Buchan ◽  
Hannah Chung ◽  
Michael Campitelli ◽  
Kevin Schwartz ◽  
...  
Keyword(s):  
Older Adults ◽  
Influenza Vaccine ◽  
Respiratory Viruses ◽  
Vaccine Effectiveness ◽  
Community Dwelling ◽  
Administrative Databases ◽  
Test Results ◽  
Illness Onset ◽  
Specimen Collection ◽  
Respiratory Specimens

IntroductionAnnual evaluation of influenza vaccine effectiveness (VE) is required because of frequent changes to circulating and vaccine strains. Traditionally, VE studies enroll patients who fulfill case definitions for respiratory infections and are tested for influenza. VE estimates generated from convenience samples of routinely collected specimens might be biased. Objectives and ApproachWe assessed the validity of using data from respiratory specimens collected during clinical encounters to estimate VE. We created the Flu and Other Respiratory Viruses Research (FOREVER) Cohort by linking respiratory virus laboratory test results from 2009-2014 from 11 public health and 8 hospital laboratories across Ontario to health administrative databases, including databases with billing claims for physician- and pharmacist-administered influenza vaccines. We evaluated the presence of information and selection biases when using these data and estimated VE in community-dwelling older adults (>65) using the test-negative design under conditions that emulated the inclusion criteria in traditional VE studies. ResultsThe FOREVER Cohort included test results from 283,711 respiratory specimens obtained from 216,730 individuals. The overall linkage proportion to health administrative databases using deterministic and probabilistic linkage methods was 97.5%. Influenza positivity for older adults with unknown lag between illness onset and specimen collection was similar to those for whom illness onset date was documented to be ≤7 days before specimen collection, suggesting minimal outcome misclassification associated with information bias. The likelihood of influenza testing was similar between vaccinated and unvaccinated individuals, suggesting an absence of selection bias that could arise when a case definition for influenza testing is not employed. Lastly, VE estimates were similar under various conditions, demonstrating the robustness of using these data, and were comparable to published estimates. Conclusion/ImplicationsThe FOREVER Cohort can be used to estimate VE with negligible bias. Compared to traditional VE studies that are limited to recruited patients, routinely collected specimens create a larger, more generalizable sample. Linkage to health administrative databases can identify those with comorbidities and permit evaluation of VE in high-risk groups.

Sign in / Sign up

Export Citation Format

Share Document