Query: effectiveness of covid 19 vaccines

title: Effectiveness of Covid 19 Vaccines against the B.1.617.2 (Delta) Variant
abstract: The B.1.617.2 (delta) variant of the severe acute respiratory syndrome coronavirus 2 (SARS CoV 2) the virus that causes coronavirus disease 2019 (Covid 19) has contributed to a surge in cases in India and has now been detected across the globe, including a notable increase in cases in the United Kingdom. The effectiveness of the BNT162b2 and ChAdOx1 nCoV 19 vaccines against this variant has been unclear.  We used a test negative case control design to estimate the effectiveness of vaccination against symptomatic disease caused by the delta variant or the predominant strain (B.1.1.7, or alpha variant) over the period that the delta variant began circulating. Variants were identified with the use of sequencing and on the basis of the spike (S) gene status. Data on all symptomatic sequenced cases of Covid 19 in England were used to estimate the proportion of cases with either variant according to the patients' vaccination status.  Effectiveness after one dose of vaccine (BNT162b2 or ChAdOx1 nCoV 19) was notably lower among persons with the delta variant (30.7% 95% confidence interval [CI] 25.2 to 35.7) than among those with the alpha variant (48.7% 95% CI, 45.5 to 51.7) the results were similar for both vaccines. With the BNT162b2 vaccine, the effectiveness of two doses was 93.7% (95% CI, 91.6 to 95.3) among persons with the alpha variant and 88.0% (95% CI, 85.3 to 90.1) among those with the delta variant. With the ChAdOx1 nCoV 19 vaccine, the effectiveness of two doses was 74.5% (95% CI, 68.4 to 79.4) among persons with the alpha variant and 67.0% (95% CI, 61.3 to 71.8) among those with the delta variant.  Only modest differences in vaccine effectiveness were noted with the delta variant as compared with the alpha variant after the receipt of two vaccine doses. Absolute differences in vaccine effectiveness were more marked after the receipt of the first dose. This finding would support efforts to maximize vaccine uptake with two doses among vulnerable populations.

title: Effectiveness of COVID 19 vaccines against the B.1.617.2 variant
abstract: The B.1.617.2 COVID 19 variant has contributed to the surge in cases in India and has now been detected across the globe, including a notable increase in cases in the UK. We estimate the effectiveness of the BNT162b2 and ChAdOx1 COVID 19 vaccines against this variant.  A test negative case control design was used to estimate the effectiveness of vaccination against symptomatic disease with both variants over the period that B.1.617.2 began circulating with cases identified based on sequencing and S gene target status. Data on all symptomatic sequenced cases of COVID 19 in England was used to estimate the proportion of cases with B.1.617.2 compared to the predominant strain (B.1.1.7) by vaccination status.  Effectiveness was notably lower after 1 dose of vaccine with B.1.617.2 cases 33.5% (95%CI: 20.6 to 44.3) compared to B.1.1.7 cases 51.1% (95%CI: 47.3 to 54.7) with similar results for both vaccines. With BNT162b2 2 dose effectiveness reduced from 93.4% (95%CI: 90.4 to 95.5) with B.1.1.7 to 87.9% (95%CI: 78.2 to 93.2) with B.1.617.2. With ChAdOx1 2 dose effectiveness reduced from 66.1% (95% CI: 54.0 to 75.0) with B.1.1.7 to 59.8% (95%CI: 28.9 to 77.3) with B.1.617.2. Sequenced cases detected after 1 or 2 doses of vaccination had a higher odds of infection with B.1.617.2 compared to unvaccinated cases (OR 1.40; 95%CI: 1.13 1.75)  After 2 doses of either vaccine there were only modest differences in vaccine effectiveness with the B.1.617.2 variant. Absolute differences in vaccine effectiveness were more marked with dose 1. This would support maximising vaccine uptake with two doses among vulnerable groups.

title: Effectiveness of COVID 19 vaccines against variants of concern, Canada
abstract: To estimate the effectiveness of BNT162b2 (Pfizer BioNTech) mRNA 1273 (Moderna) and ChAdOx1 (AstraZeneca) vaccines against symptomatic SARS CoV 2 infection and severe outcomes (COVID 19 hospitalization or death) caused by the Alpha (B.1.1.7) Beta (B.1.351) Gamma (P.1) and Delta (B.1.617.2) variants of concern (VOCs) during December 2020 to May 2021.  We conducted a test negative design study using linked population wide vaccination, laboratory testing, and health administrative databases in Ontario, Canada.  Against symptomatic infection caused by Alpha, vaccine effectiveness with partial vaccination ]14 days after dose 1) was higher for mRNA 1273 than BNT162b2 and ChAdOx1. Full vaccination ]7 days after dose 2) increased vaccine effectiveness for BNT162b2 and mRNA 1273 against Alpha. Protection against symptomatic infection caused by Beta/Gamma was lower with partial vaccination for ChAdOx1 than mRNA 1273. Against Delta, vaccine effectiveness after partial vaccination tended to be lower than against Alpha for BNT162b2 and mRNA 1273, but was similar to Alpha for ChAdOx1. Full vaccination with BNT162b2 increased protection against Delta to levels comparable to Alpha and Beta/Gamma. Vaccine effectiveness against hospitalization or death caused by all studied VOCs was generally higher than for symptomatic infection after partial vaccination with all three vaccines.  Our findings suggest that even a single dose of these 3 vaccine products provide good to excellent protection against symptomatic infection and severe outcomes caused by the 4 currently circulating variants of concern, and that 2 doses are likely to provide even higher protection.

title: Effectiveness of COVID 19 Vaccines in Preventing SARS CoV 2 Infection Among Frontline Workers Before and During B.1.617.2 (Delta) Variant Predominance Eight U.S. Locations, December 2020 August 2021
abstract: During December 14, 2020 April 10, 2021, data from the HEROES RECOVER Cohorts, a network of prospective cohorts among frontline workers, showed that the Pfizer BioNTech and Moderna mRNA COVID 19 vaccines were approximately 90% effective in preventing symptomatic and asymptomatic infection with SARS CoV 2, the virus that causes COVID 19, in real world conditions (1,2) This report updates vaccine effectiveness (VE) estimates including all COVID 19 vaccines available through August 14, 2021, and examines whether VE differs for adults with increasing time since completion of all recommended vaccine doses. VE before and during SARS CoV 2 B.1.617.2 (Delta) variant predominance, which coincided with an increase in reported COVID 19 vaccine breakthrough infections, were compared (3,4)

title: Effectiveness of COVID 19 Vaccines in Preventing Hospitalization Among Adults Aged =65 Years COVID NET, 13 States, February April 2021
abstract: Clinical trials of COVID 19 vaccines currently authorized for emergency use in the United States (Pfizer BioNTech, Moderna, and Janssen [Johnson Johnson] indicate that these vaccines have high efficacy against symptomatic disease, including moderate to severe illness (1 3) In addition to clinical trials, real world assessments of COVID 19 vaccine effectiveness are critical in guiding vaccine policy and building vaccine confidence, particularly among populations at higher risk for more severe illness from COVID 19, including older adults. To determine the real world effectiveness of the three currently authorized COVID 19 vaccines among persons aged =65 years during February 1 April 30, 2021, data on 7,280 patients from the COVID 19 Associated Hospitalization Surveillance Network (COVID NET) were analyzed with vaccination coverage data from state immunization information systems (IISs) for the COVID NET catchment area (approximately 4.8 million persons) Among adults aged 65 74 years, effectiveness of full vaccination in preventing COVID 19 associated hospitalization was 96% (95% confidence interval [CI] 94% 98% for Pfizer BioNTech, 96% (95% CI 95% 98% for Moderna, and 84% (95% CI 64% 93% for Janssen vaccine products. Effectiveness of full vaccination in preventing COVID 19 associated hospitalization among adults aged =75 years was 91% (95% CI 87% 94% for Pfizer BioNTech, 96% (95% CI 93% 98% for Moderna, and 85% (95% CI 72% 92% for Janssen vaccine products. COVID 19 vaccines currently authorized in the United States are highly effective in preventing COVID 19 associated hospitalizations in older adults. In light of real world data demonstrating high effectiveness of COVID 19 vaccines among older adults, efforts to increase vaccination coverage in this age group are critical to reducing the risk for COVID 19 related hospitalization.

title: Effectiveness of Covid 19 Vaccines in Ambulatory and Inpatient Care Settings
abstract: There are limited data on the effectiveness of the vaccines against symptomatic coronavirus disease 2019 (Covid 19) currently authorized in the United States with respect to hospitalization, admission to an intensive care unit (ICU) or ambulatory care in an emergency department or urgent care clinic.  We conducted a study involving adults =50 years of age) with Covid 19 like illness who underwent molecular testing for severe acute respiratory syndrome coronavirus 2 (SARS CoV 2) We assessed 41,552 admissions to 187 hospitals and 21,522 visits to 221 emergency departments or urgent care clinics during the period from January 1 through June 22, 2021, in multiple states. The patients' vaccination status was documented in electronic health records and immunization registries. We used a test negative design to estimate vaccine effectiveness by comparing the odds of a positive test for SARS CoV 2 infection among vaccinated patients with those among unvaccinated patients. Vaccine effectiveness was adjusted with weights based on propensity for vaccination scores and according to age, geographic region, calendar time (days from January 1, 2021, to the index date for each medical visit) and local virus circulation.  The effectiveness of full messenger RNA (mRNA) vaccination =14 days after the second dose) was 89% (95% confidence interval [CI] 87 to 91) against laboratory confirmed SARS CoV 2 infection leading to hospitalization, 90% (95% CI, 86 to 93) against infection leading to an ICU admission, and 91% (95% CI, 89 to 93) against infection leading to an emergency department or urgent care clinic visit. The effectiveness of full vaccination with respect to a Covid 19 associated hospitalization or emergency department or urgent care clinic visit was similar with the BNT162b2 and mRNA 1273 vaccines and ranged from 81% to 95% among adults 85 years of age or older, persons with chronic medical conditions, and Black or Hispanic adults. The effectiveness of the Ad26.COV2.S vaccine was 68% (95% CI, 50 to 79) against laboratory confirmed SARS CoV 2 infection leading to hospitalization and 73% (95% CI, 59 to 82) against infection leading to an emergency department or urgent care clinic visit.  Covid 19 vaccines in the United States were highly effective against SARS CoV 2 infection requiring hospitalization, ICU admission, or an emergency department or urgent care clinic visit. This vaccine effectiveness extended to populations that are disproportionately affected by SARS CoV 2 infection. (Funded by the Centers for Disease Control and Prevention.

title: Efficacy and effectiveness of COVID 19 vaccines against SARS CoV 2 infection: interim results of a living systematic review, 1 January to 14 May 2021
abstract: Evidence on COVID 19 vaccine efficacy/effectiveness (VE) in preventing asymptomatic SARS CoV 2 infections is needed to guide public health recommendations for vaccinated people. We report interim results of a living systematic review. We identified a total of 30 studies that investigated VE against symptomatic and/or asymptomatic infection. In fully vaccinated individuals, VE against symptomatic and asymptomatic infections was 80 90% in nearly all studies. Fully vaccinated persons are less likely to become infected and contribute to transmission.

title: Effectiveness of COVID 19 vaccines in preventing SARS CoV 2 infection and hospitalisation, Navarre, Spain, January to April 2021
abstract: COVID 19 vaccine effectiveness was evaluated in close contacts of cases diagnosed during January April 2021. Among 20,961 contacts, 7,240 SARS CoV 2 infections were confirmed, with 5,467 being symptomatic and 559 leading to hospitalisations. Non brand specific one and two dose vaccine effectiveness were respectively, 35% (95% confidence interval (CI) 25 to 44) and 66% (95% CI: 57 to 74) against infections, 42% (95% CI: 31 to 52) and 82% (95% CI: 74 to 88) against symptomatic infection, and 72% (95% CI: 47 to 85) and 95% (95% CI: 62 to 99) against COVID 19 hospitalisation. The second dose significantly increased effectiveness. Findings support continuing complete vaccination.

title: Effectiveness of First Dose of COVID 19 Vaccines Against Hospital Admissions in Scotland: National Prospective Cohort Study of 5.4 Million People
abstract: The BNT162b2 mRNA (Pfizer BioNTech) and ChAdOx1 (Oxford AstraZeneca) COVID 19 vaccines have demonstrated high efficacy against infection in phase 3 clinical trials and are now being used in national vaccination programmes in the UK and several other countries. There is an urgent need to study the 'real world' effects of these vaccines. The aim of our study was to estimate the effectiveness of the first dose of these COVID 19 vaccines in preventing hospital admissions.  We conducted a prospective cohort study using the Early Pandemic Evaluation and Enhanced Surveillance of COVID 19 (EAVE II) database comprising of linked vaccination, primary care, Real Time Polymerase Chain Reaction (RT PCR) testing, hospitalisation and mortality records for 5.4 million people in Scotland (covering ~99% of population) A time dependent Cox model and Poisson regression models were fitted to estimate effectiveness against COVID 19 related hospitalisation (defined as 1 Adjusted Hazard Ratio) following the first dose of vaccine.  The first dose of the BNT162b2 vaccine was associated with a vaccine effect of 85% (95% confidence interval [CI] 76 to 91) for COVID 19 related hospitalisation at 28 34 days post vaccination. Vaccine effect at the same time interval for the ChAdOx1 vaccine was 94% (95% CI 73 to 99) Results of combined vaccine effect for prevention of COVID 19 related hospitalisation were comparable when restricting the analysis to those aged =80 years (81% 95% CI 65 to 90 at 28 34 days post vaccination)  A single dose of the BNT162b2 mRNA and ChAdOx1 vaccines resulted in substantial reductions in the risk of COVID 19 related hospitalisation in Scotland.  Research and Innovation Industrial Strategy Challenge Fund; Health Data Research UK. Conflict of Interest: AS is a member of the Scottish Government Chief Medical Officer's COVID 19Advisory Group and the New and Emerging Respiratory Virus Threats (NERVTAG) Risk Stratification Subgroup. CRS declares funding from the MRC, NIHR, CSO and New Zealand Ministry for Business, Innovation and Employment and Health Research Council during the conduct of this study. SVK is co chair of the Scottish Government's Expert Reference Group on COVID 19 and ethnicity, is a member of the Scientific Advisory Group on Emergencies (SAGE) subgroup on ethnicity and acknowledges funding from a NRS Senior Clinical Fellowship, MRC and CSO. All other authors report no conflicts of interest. Ethical Approval: Approvals were obtained from the National Research Ethics Service Committee, Southeast Scotland 02 (reference number: 12/SS/0201) and Public Benefit and Privacy Panel for Health and Social Care (reference number: 1920 0279)

title: Real World Effectiveness of COVID 19 Vaccines: the Diverging Pattern of COVID 19 Cases and Deaths in Countries with High Vaccination Rates
abstract: Vaccines have played an important role in minimizing COVID 19 cases and deaths. Clinical trials of vaccines have suggested high efficacy against the SARS CoV 2 virus. Here we evaluate the real world efficacy of inactivated virus, viral vector, and mRNA COVID 19 vaccines. For our analysis, we chose 7 countries with a population 1 million that have partially vaccinated 50% of their population by May 30, 2021. In some countries, the number of cases and deaths have declined significantly, whereas in others they have increased compared to the pre vaccination levels. The data suggest that countries using mRNA based vaccines have been the most effective in reducing the number of COVID 19 cases and deaths. The observed patterns could be due to the higher efficacy of mRNA based vaccines. Additionally, the large difference in real world and clinical trials for some of the vaccines can be attributed to the non representative population sampling during clinical trials.