Increased disparity in routine infant vaccination during COVID-19

BackgroundCOVID-19 restrictions and its impact on healthcare resources have reduced routine infant vaccine uptake, although some report that this effect was short-lived. These prior studies mostly described entire populations, but disparities in uptake may have changed during the pandemic due to differential access to healthcare. ObjectivesWe aimed to examine disparities in the reduction in routine infant vaccine uptake during the COVID-19 pandemic in Manitoba, Canada. MethodsWe assessed vaccine uptake for routine infant vaccines for a pre-pandemic and pandemic subcohort. We assessed how the reduction in vaccine uptake differed by gender, neighborhood income quintile and region of residence. For each evaluation age, we limited the pandemic subcohort to children reaching this milestone age on/before November 30, 2021. ResultsVaccine uptake was about 5-10% lower during the pandemic. The groups most vulnerable to COVID-19 saw the largest reductions in vaccine uptake, with an ongoing downward trend throughout the pandemic. Children in the lowest income neighborhoods saw a 17% reduction in diphtheria, tetanus, and acellular pertussis dose 4 uptake at 24 months, 4.4-fold that of high-income neighborhoods, and an 11% reduction in measles, mumps, rubella (MMR) vaccine uptake at 24 months, 5.6-fold that of high-income neighborhoods. The largest reductions were for low-income Northern residents and smallest for high-income Winnipeg residents, e.g. 16-fold larger for MMR at 24 months (79:94 pre-pandemic to 65:93 during the pandemic). ConclusionsWhile privileged children have similar high vaccine uptake as before the pandemic, children in populations hardest hit by COVID-19 continue seeing concerning reductions in routine infant vaccination. It is imperative that infant vaccination rates are increased, especially in communities with lower socioeconomic status, as a failure to do so could lead to persistent rebound epidemics in the most vulnerable populations. SynopsisO_ST_ABSStudy questionC_ST_ABSHow did COVID-19 and its restrictions affect routine infant vaccine uptake? Whats already knownWe know that vaccine uptake in infants decreased during the pandemic. We do not know whether this affected everyone equally or whether the pandemic worsened existing disparities in vaccine uptake. What this study addsAlthough vaccine uptake was not affected in wealthy urban neighborhoods, the reduction in uptake was largest, and continued on a downward trend, for groups with the lowest baseline vaccine uptake. Only two-thirds of children, instead of the 4/5th before the pandemic, in the remote, predominantly Indigenous Northern region received a measles vaccine by their second birthday.

Effectiveness of COVID-19 vaccines against hospitalization and death in Canada: A multiprovincial test-negative design study

BackgroundA major goal of COVID-19 vaccination is to prevent severe outcomes (hospitalizations and deaths). We estimated the effectiveness of mRNA and ChAdOx1 COVID-19 vaccines against severe outcomes in four Canadian provinces between December 2020 and September 2021. MethodsWe conducted this multiprovincial retrospective test-negative study among community-dwelling adults aged [≥]18 years in Ontario, Quebec, British Columbia, and Manitoba using linked provincial databases and a common study protocol. Multivariable logistic regression was used to estimate province-specific vaccine effectiveness against COVID-19 hospitalization and/or death. Estimates were pooled using random effects models. ResultsWe included 2,508,296 tested subjects, with 31,776 COVID-19 hospitalizations and 5,842 deaths. Vaccine effectiveness was 83% after a first dose, and 98% after a second dose, against both hospitalization and death (separately). Against severe outcomes (hospitalization or death), effectiveness was 87% (95%CI: 71%-94%) [≥]84 days after a first dose of mRNA vaccine, increasing to 98% (95%CI: 96%-99%) [≥]112 days after a second dose. Vaccine effectiveness against severe outcomes for ChAdOx1 was 88% (95%CI: 75%-94%) [≥]56 days after a first dose, increasing to 97% (95%CI: 91%-99%) [≥]56 days after a second dose. Lower one-dose effectiveness was observed for adults aged [≥]80 years and those with comorbidities, but effectiveness became comparable after a second dose. Two doses of vaccines provided very high protection for both homologous and heterologous schedules, and against Alpha, Gamma, and Delta variants. ConclusionsTwo doses of mRNA or ChAdOx1 vaccines provide excellent protection against severe outcomes of hospitalization and death.

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

ObjectivesTo estimate the effectiveness of mRNA COVID-19 vaccines against symptomatic infection and severe outcomes. DesignWe applied a test-negative design study to linked laboratory, vaccination, and health administrative databases, and used multivariable logistic regression adjusting for demographic and clinical characteristics associated with SARS-CoV-2 and vaccine receipt to estimate vaccine effectiveness (VE) against symptomatic infection and severe outcomes. SettingOntario, Canada between 14 December 2020 and 19 April 2021. ParticipantsCommunity-dwelling adults aged [≥]16 years who had COVID-19 symptoms and were tested for SARS-CoV-2. InterventionsPfizer-BioNTechs BNT162b2 or Modernas mRNA-1273 vaccine. Main outcome measuresLaboratory-confirmed SARS-CoV-2 by RT-PCR; hospitalization/death associated with SARS-CoV-2 infection. ResultsAmong 324,033 symptomatic individuals, 53,270 (16.4%) were positive for SARS-CoV-2 and 21,272 (6.6%) received [≥]1 vaccine dose. Among test-positive cases, 2,479 (4.7%) had a severe outcome. VE against symptomatic infection [≥]14 days 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. VE [≥]7 days after 2 doses was 91% (95%CI, 89 to 93%). Against severe outcomes, VE [≥]14 days after 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, whereas VE [≥]7 days after 2 doses was 98% (95%CI, 88 to 100%). For adults aged [≥]70 years, VE estimates were lower for intervals shortly after receiving 1 dose, but were comparable to younger adults for all intervals after 28 days. After 2 doses, we observed high VE against E484K-positive variants. ConclusionsTwo doses of mRNA COVID-19 vaccines are highly effective against symptomatic infection and severe outcomes. Single-dose effectiveness is lower, particularly for older adults shortly after the first dose.

Background rates of hospitalizations and emergency department visits for selected thromboembolic and coagulation disorders in Ontario, Canada, 2015 to 2020, to inform COVID-19 vaccine safety surveillance

ObjectiveThe objective of this study was to estimate background rates of selected thromboembolic and coagulation disorders in Ontario, Canada. DesignPopulation-based retrospective observational study using linked health administrative databases. Records of hospitalizations and emergency department visits were searched to identify cases using diagnostic codes from the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, Canada (ICD-10-CA). ParticipantsAll Ontario residents. Primary outcome measuresIncidence rates of stroke, deep vein thrombosis, pulmonary embolism, idiopathic thrombocytopenia, disseminated intravascular coagulation, and cerebral venous thrombosis during five pre-pandemic years (2015-2019, annually, averaged, and monthly average) and 2020. ResultsThe average annual population was 14 million with 51% female. The mean annual rates during 2015-2019 were 127.1/100,000 population (95% confidence interval [CI], 126.2, 127.9) for ischemic stroke, 22.0/100,000 (95%CI, 21.6, 22.3) for intracerebral haemorrhage, 9.4 (95%CI, 9.2, 9.7) for subarachnoid haemorrhage, 86.8/100,000 (95%CI, 86.1, 87.5) for deep vein thrombosis, 63.7/100,000 (95%CI, 63.1, 64.3) for pulmonary embolism, 6.1/100,000 (95%CI, 5.9, 6.3) for idiopathic thrombocytopenia, 1.6/100,000 (95%CI, 1.5, 1.7) for disseminated intravascular coagulation, and 1.5/100,000 (95%CI, 1.4, 1.6) for cerebral venous thrombosis. Rates were lower in 2020 than during the pre-pandemic years for ischemic stroke, deep vein thrombosis, and idiopathic thrombocytopenia. Rates were generally consistent over time, except for pulmonary embolism, which increased from 57.1 to 68.5 per 100,000 between 2015 and 2019. Rates were higher for females than males for subarachnoid haemorrhage, pulmonary embolism, and cerebral venous thrombosis, and vice versa for ischemic stroke and intracerebral haemorrhage. Rates increased with age for most of these conditions, but idiopathic thrombocytopenia demonstrated a bimodal distribution with incidence peaks at 0-19 years and [≥]60 years. ConclusionsOur estimated background rates help to contextualize observed events of these potential adverse events of special interest and to detect potential safety signals related to COVID-19 vaccines. Strengths and limitations of this study[tpltrtarr] Recent background rates of selected thromboembolic and coagulation disorders that are potential adverse events special interest related to COVID-19 vaccine are estimated. [tpltrtarr]Background rates during five pre-pandemic (2015-2019) years and 2020 will provide context for these events to identify vaccine safety signals. [tpltrtarr]We used recorded diagnostic codes in administrative data without information on clinical and/or diagnostic confirmation, and the validity of these data are imperfect, which may result in under or overestimation.