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1.
J Infect ; 2022 Apr 08.
Article in English | MEDLINE | ID: covidwho-1778314

ABSTRACT

OBJECTIVES: To monitor changes in seroprevalence of SARS-CoV-2 antibodies in populations over time and between different demographic groups. METHODS: A subset of practices in the Oxford-Royal College of General Practitioners (RCGP) Research and Surveillance Centre (RSC) sentinel network provided serum samples, collected when volunteer patients had routine blood tests. We tested these samples for SARS-CoV-2 antibodies using Abbott (Chicago, USA), Roche (Basel, Switzerland) and/or Euroimmun (Luebeck, Germany) assays, and linked the results to the patients' primary care computerised medical records. We report seropositivity by region and age group, and additionally examined the effects of gender, ethnicity, deprivation, rurality, shielding recommendation and smoking status. RESULTS: We estimated seropositivity from patients aged 18-100 years old, which ranged from 4.1% (95% CI 3.1-5.3%) to 8.9% (95% CI 7.8-10.2%) across the different assays and time periods. We found higher Euroimmun seropositivity in younger age groups, people of Black and Asian ethnicity (compared to white), major conurbations, and non-smokers. We did not observe any significant effect by region, gender, deprivation, or shielding recommendation. CONCLUSIONS: Our results suggest that prior to the vaccination programme, most of the population remained unexposed to SARS-CoV-2.

2.
Nat Med ; 2022 Jan 14.
Article in English | MEDLINE | ID: covidwho-1740457

ABSTRACT

Booster vaccination with messenger RNA (mRNA) vaccines has been offered to adults in England starting on 14 September 2021. We used a test-negative case-control design to estimate the relative effectiveness of a booster dose of BNT162b2 (Pfizer-BioNTech) compared to only a two-dose primary course (at least 175 days after the second dose) or unvaccinated individuals from 13 September 2021 to 5 December 2021, when Delta variant was dominant in circulation. Outcomes were symptomatic coronavirus disease 2019 (COVID-19) and hospitalization. The relative effectiveness against symptomatic disease 14-34 days after a BNT162b2 or mRNA-1273 (Moderna) booster after a ChAdOx1-S (AstraZeneca) and BNT162b2 as a primary course ranged from around 85% to 95%. Absolute vaccine effectiveness ranged from 94% to 97% and was similar in all age groups. Limited waning was seen 10 or more weeks after the booster. Against hospitalization or death, absolute effectiveness of a BNT162b2 booster ranged from around 97% to 99% in all age groups irrespective of the primary course, with no evidence of waning up to 10 weeks. This study provides real-world evidence of substantially increased protection from the booster vaccine dose against mild and severe disease irrespective of the primary course.

3.
N Engl J Med ; 2022 Mar 02.
Article in English | MEDLINE | ID: covidwho-1730372

ABSTRACT

BACKGROUND: A rapid increase in coronavirus disease 2019 (Covid-19) cases due to the omicron (B.1.1.529) variant of severe acute respiratory syndrome coronavirus 2 in highly vaccinated populations has aroused concerns about the effectiveness of current vaccines. METHODS: We used a test-negative case-control design to estimate vaccine effectiveness against symptomatic disease caused by the omicron and delta (B.1.617.2) variants in England. Vaccine effectiveness was calculated after primary immunization with two doses of BNT162b2 (Pfizer-BioNTech), ChAdOx1 nCoV-19 (AstraZeneca), or mRNA-1273 (Moderna) vaccine and after a booster dose of BNT162b2, ChAdOx1 nCoV-19, or mRNA-1273. RESULTS: Between November 27, 2021, and January 12, 2022, a total of 886,774 eligible persons infected with the omicron variant, 204,154 eligible persons infected with the delta variant, and 1,572,621 eligible test-negative controls were identified. At all time points investigated and for all combinations of primary course and booster vaccines, vaccine effectiveness against symptomatic disease was higher for the delta variant than for the omicron variant. No effect against the omicron variant was noted from 20 weeks after two ChAdOx1 nCoV-19 doses, whereas vaccine effectiveness after two BNT162b2 doses was 65.5% (95% confidence interval [CI], 63.9 to 67.0) at 2 to 4 weeks, dropping to 8.8% (95% CI, 7.0 to 10.5) at 25 or more weeks. Among ChAdOx1 nCoV-19 primary course recipients, vaccine effectiveness increased to 62.4% (95% CI, 61.8 to 63.0) at 2 to 4 weeks after a BNT162b2 booster before decreasing to 39.6% (95% CI, 38.0 to 41.1) at 10 or more weeks. Among BNT162b2 primary course recipients, vaccine effectiveness increased to 67.2% (95% CI, 66.5 to 67.8) at 2 to 4 weeks after a BNT162b2 booster before declining to 45.7% (95% CI, 44.7 to 46.7) at 10 or more weeks. Vaccine effectiveness after a ChAdOx1 nCoV-19 primary course increased to 70.1% (95% CI, 69.5 to 70.7) at 2 to 4 weeks after an mRNA-1273 booster and decreased to 60.9% (95% CI, 59.7 to 62.1) at 5 to 9 weeks. After a BNT162b2 primary course, the mRNA-1273 booster increased vaccine effectiveness to 73.9% (95% CI, 73.1 to 74.6) at 2 to 4 weeks; vaccine effectiveness fell to 64.4% (95% CI, 62.6 to 66.1) at 5 to 9 weeks. CONCLUSIONS: Primary immunization with two doses of ChAdOx1 nCoV-19 or BNT162b2 vaccine provided limited protection against symptomatic disease caused by the omicron variant. A BNT162b2 or mRNA-1273 booster after either the ChAdOx1 nCoV-19 or BNT162b2 primary course substantially increased protection, but that protection waned over time. (Funded by the U.K. Health Security Agency.).

5.
EuropePMC; 2021.
Preprint in English | EuropePMC | ID: ppcovidwho-322164

ABSTRACT

Background: We investigated the effect of both doses of either BNT162b2 or ChAdOx-1 vaccine among residents of Long-term care facilities (LTCFs) in England. This cohort is at particularly high risk for severe outcomes related to COVID-19 and is regularly tested regardless of symptoms.Methods: This observational study uses testing, immunisation and mortality data from 8 December 2020 to 25 June 2021 in LTCF residents aged 65 years and above. Cox proportional hazards models were used to derive adjusted hazard ratios (aHR) for the risk of infection and death within 28 days of positive test result, adjusted for sex, age-group, previous infection, deprivation, and incidence rate in the local authority area. The impact of interval between first and second dose was also explored. Findings: Of 219733 LTCF residents, 41828 (19%) had a positive test and 10719 (4.9%) died within 28 days of a positive test during the study period. Relative to unvaccinated individuals, aHR for infection were lowest at 0.43 (95% CI 0.35-0.52) 36-49 days after first dose and 0.27 (0.20-0.38) at 29-60 days following second dose . Against death, aHR was lowest at 0.25 (0.20-0.31) 28-56 days after first dose and 0.13 (0-05-0.32) in the 1-14 days after second dose. As expected, some waning of protection against infection was observed after seven weeks from first dose which persisted to 2-4 weeks following second dose. Interpretation: Vaccination with one dose of BNT162b2 and ChAdOx-1 provides moderate protection against infection and death in residents in LTCFs. Protection is strong after two doses.Funding: None to declare.Declaration of Interest: None to declare. Ethical Approval: Vaccine effectiveness studies are undertaken by Public Health England as part of ongoing surveillance activities and did not require ethical approval.

6.
N Engl J Med ; 386(4): 340-350, 2022 01 27.
Article in English | MEDLINE | ID: covidwho-1621313

ABSTRACT

BACKGROUND: Vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (Covid-19), have been used since December 2020 in the United Kingdom. Real-world data have shown the vaccines to be highly effective against Covid-19 and related severe disease and death. Vaccine effectiveness may wane over time since the receipt of the second dose of the ChAdOx1-S (ChAdOx1 nCoV-19) and BNT162b2 vaccines. METHODS: We used a test-negative case-control design to estimate vaccine effectiveness against symptomatic Covid-19 and related hospitalization and death in England. Effectiveness of the ChAdOx1-S and BNT162b2 vaccines was assessed according to participant age and status with regard to coexisting conditions and over time since receipt of the second vaccine dose to investigate waning of effectiveness separately for the B.1.1.7 (alpha) and B.1.617.2 (delta) variants. RESULTS: Vaccine effectiveness against symptomatic Covid-19 with the delta variant peaked in the early weeks after receipt of the second dose and then decreased by 20 weeks to 44.3% (95% confidence interval [CI], 43.2 to 45.4) with the ChAdOx1-S vaccine and to 66.3% (95% CI, 65.7 to 66.9) with the BNT162b2 vaccine. Waning of vaccine effectiveness was greater in persons 65 years of age or older than in those 40 to 64 years of age. At 20 weeks or more after vaccination, vaccine effectiveness decreased less against both hospitalization, to 80.0% (95% CI, 76.8 to 82.7) with the ChAdOx1-S vaccine and 91.7% (95% CI, 90.2 to 93.0) with the BNT162b2 vaccine, and death, to 84.8% (95% CI, 76.2 to 90.3) and 91.9% (95% CI, 88.5 to 94.3), respectively. Greater waning in vaccine effectiveness against hospitalization was observed in persons 65 years of age or older in a clinically extremely vulnerable group and in persons 40 to 64 years of age with underlying medical conditions than in healthy adults. CONCLUSIONS: We observed limited waning in vaccine effectiveness against Covid-19-related hospitalization and death at 20 weeks or more after vaccination with two doses of the ChAdOx1-S or BNT162b2 vaccine. Waning was greater in older adults and in those in a clinical risk group.


Subject(s)
COVID-19/prevention & control , Adolescent , Adult , Age Factors , Aged , COVID-19/mortality , COVID-19/virology , Case-Control Studies , Female , Hospitalization/statistics & numerical data , Humans , Immunization, Secondary , Immunogenicity, Vaccine , Male , Middle Aged , Patient Acuity , Risk Factors , SARS-CoV-2 , Time Factors , United Kingdom/epidemiology
7.
EuropePMC; 2021.
Preprint in English | EuropePMC | ID: ppcovidwho-296519

ABSTRACT

Abstract Background A rapid increase in cases due to the SARS-CoV-2 Omicron (B.1.1.529) variant in highly vaccinated populations has raised concerns about the effectiveness of current vaccines. Methods We used a test-negative case-control design to estimate vaccine effectiveness (VE) against symptomatic disease caused by the Omicron and Delta variants in England. VE was calculated after primary immunisation with two BNT162b2 or ChAdOx1 doses, and at 2+ weeks following a BNT162b2 booster. Results Between 27 November and 06 December 2021, 581 and 56,439 eligible Omicron and Delta cases respectively were identified. There were 130,867 eligible test-negative controls. There was no effect against Omicron from 15 weeks after two ChAdOx1 doses, while VE after two BNT162b2 doses was 88.0% (95%CI: 65.9 to 95.8%) 2-9 weeks after dose 2, dropping to between 34 and 37% from 15 weeks post dose 2.From two weeks after a BNT162b2 booster, VE increased to 71.4% (95%CI: 41.8 to 86.0%) for ChAdOx1 primary course recipients and 75.5% (95%CI: 56.1 to 86.3%) for BNT162b2 primary course recipients. For cases with Delta, VE was 41.8% (95%CI: 39.4-44.1%) at 25+ weeks after two ChAdOx1 doses, increasing to 93.8% (95%CI: 93.2-94.3%) after a BNT162b2 booster. With a BNT162b2 primary course, VE was 63.5% (95%CI: 61.4 to 65.5%) 25+ weeks after dose 2, increasing to 92.6% (95%CI: 92.0-93.1%) two weeks after the booster. Conclusions Primary immunisation with two BNT162b2 or ChAdOx1 doses provided no or limited protection against symptomatic disease with the Omicron variant. Boosting with BNT162b2 following either primary course significantly increased protection.

8.
Nat Commun ; 12(1): 7217, 2021 12 10.
Article in English | MEDLINE | ID: covidwho-1565716

ABSTRACT

The UK prioritised delivery of the first dose of BNT162b2 (Pfizer/BioNTech) and AZD1222 (AstraZeneca) vaccines by extending the interval between doses up to 12 weeks. In 750 participants aged 50-89 years, we here compare serological responses after BNT162b2 and AZD1222 vaccination with varying dose intervals, and evaluate these against real-world national vaccine effectiveness (VE) estimates against COVID-19 in England. We show that antibody levels 14-35 days after dose two are higher in BNT162b2 recipients with an extended vaccine interval (65-84 days) compared with those vaccinated with a standard (19-29 days) interval. Following the extended schedule, antibody levels were 6-fold higher at 14-35 days post dose 2 for BNT162b2 than AZD1222. For both vaccines, VE was higher across all age-groups from 14 days after dose two compared to one dose, but the magnitude varied with dose interval. Higher dose two VE was observed with >6 week interval between BNT162b2 doses compared to the standard schedule. Our findings suggest higher effectiveness against infection using an extended vaccine schedule. Given global vaccine constraints these results are relevant to policymakers.


Subject(s)
COVID-19 Vaccines/immunology , COVID-19/prevention & control , Immunization Schedule , Aged , Aged, 80 and over , Antibodies, Viral/blood , Antibody Formation , COVID-19 Vaccines/administration & dosage , England , Female , Humans , Male , Middle Aged
9.
2021.
Preprint in English | Other preprints | ID: ppcovidwho-296143

ABSTRACT

In England, the National Immunisation Management System (NIMS) has been used to deliver COVID-19 vaccinations across England, monitor vaccine coverage, and assess vaccine effectiveness and safety. The NIMS was developed by a joint collaboration between a range of health and digital government agencies. Vaccinations delivered at large vaccination sites, pharmacies, hospitals and in primary care are entered on a point of care application which is verified using the unique NHS number in a centralised system containing information for everyone resident and registered with a GP in England. Vaccination details and additional data from hospital and GP records (such as priority groups) are sent to NHS Digital for data linkage. The NIMS constantly receives updated details from NHS Digital for all individuals and these data are provided to Public Health England (PHE) in a secure environment. PHE primarily use the NIMS for vaccine coverage, vaccine effectiveness and safety. Daily access to individual-level vaccine data has allowed PHE to rapidly and accurately estimate vaccine coverage and provide some of the world’s first vaccine effectiveness estimates. Other countries evaluating the roll-out and effect of COVID-19 vaccine programmes should consider a vaccine register or immunisation information system similar to the NIMS.

10.
EuropePMC; 2021.
Preprint in English | EuropePMC | ID: ppcovidwho-294494

ABSTRACT

Summary Background The ability of SARS-CoV-2 vaccines to protect against infection and onward transmission determines whether immunisation can control global circulation. We estimated effectiveness of BNT162b2 and ChAdOx1 vaccines against acquisition and transmission of the Alpha and Delta variants in a prospective household study in England. Methods Adult index cases in the community and their household contacts took oral-nasal swabs on days 1, 3 and 7 after enrolment. Swabs were tested by RT-qPCR with genomic sequencing conducted on a subset. We used Bayesian logistic regression to infer vaccine effectiveness against acquisition and transmission, adjusted for age, vaccination history and variant. Findings Between 2 February 2021 and 10 September 2021 213 index cases and 312 contacts were followed up. After excluding households lacking genomic proximity (N=2) or with unlikely serial intervals (N=16), 195 households with 278 contacts remained of whom 113 (41%) became PCR positive. Delta lineages had 1.64 times the risk (95% Credible Interval: 1.15 – 2.44) of transmission than Alpha;contacts older than 18 years were 1.19 times (1.04 - 1.52) more likely to acquire infection than children. Effectiveness of two doses of BNT162b2 against transmission of Delta was 31% (−3%, 61%) and 42% (14%, 69%) for ChAdOx1, similar to their effectiveness for Alpha. Protection against infection with Alpha was higher than for Delta, 71% (12%,95%) vs 24% (−2%, 64%) respectively for BNT162b2 and 26% (−39%, 73%) vs 14% (−5%, 46%) respectively for ChAdOx1. Interpretation BNT162b2 and ChAdOx1 reduce transmission of the Delta variant from breakthrough infections in the household setting though their protection against infection is low. Funding This study was funded by the UK Health Security Agency (formerly Public Health England) as part of the COVID-19 response.

12.
EuropePMC; 2021.
Preprint in English | EuropePMC | ID: ppcovidwho-292887

ABSTRACT

Background: The ability of SARS-CoV-2 vaccines to protect against infection and onward transmission determines whether immunisation can control global circulation. We estimated effectiveness of BNT162b2 and ChAdOx1 vaccines against acquisition and transmission of the Alpha and Delta variants in a prospective household study in England. Methods: Adult index cases in the community and their household contacts took oral-nasal swabs on days 1, 3 and 7 after enrolment. Swabs were tested by RT-qPCR with genomic sequencing conducted on a subset. We used Bayesian logistic regression to infer vaccine effectiveness against acquisition and transmission, adjusted for age, vaccination history and variant. Findings: Between 2 February 2021 and 10 September 2021 213 index cases and 312 contacts were followed up. After excluding households lacking genomic proximity (N=2) or with unlikely serial intervals (N=16), 195 households with 278 contacts remained of whom 113 (41%) became PCR positive. Delta lineages had 1.64 times the risk (95% Credible Interval: 1.15-2.44) of transmission than Alpha;contacts older than 18 years were 1.19 times (1.04-1.52) more likely to acquire infection than children. Effectiveness of two doses of BNT162b2 against transmission of Delta was 31% (-3%, 61%) and 42% (14%, 69%) for ChAdOx1, similar to their effectiveness for Alpha. Protection against infection with Alpha was higher than for Delta, 71% (12%,95%) vs 24% (-2%, 64%) respectively for BNT162b2 and 26% (-39%, 73%) vs 14% (-5%, 46%) respectively for ChAdOx1. Interpretation: BNT162b2 and ChAdOx1 reduce transmission of the Delta variant from breakthrough infections in the household setting though their protection against infection is low. Funding: This study was funded by the UK Health Security Agency (formerly Public Health England) as part of the COVID-19 response.

13.
EuropePMC; 2021.
Preprint in English | EuropePMC | ID: ppcovidwho-292833

ABSTRACT

Background: In September 2021, the UK Government introduced a booster programme targeting individuals over 50 and those in a clinical risk group. Individuals were offered either a full dose of the BNT162b2 (Comirnaty, Pfizer-BioNTech) vaccine or a half dose of the mRNA-1273 (Spikevax, Moderna) vaccine, irrespective of the vaccine received as the primary course Methods We used a test-negative case-control design to estimate the Vaccine Effectiveness (VE) of the booster dose BNT162b2 (Comirnaty, Pfizer-BioNTech) in those aged over 50 against symptomatic disease in post booster time intervals compared to individuals at least 140 days post a second dose with no booster dose recorded. In a secondary analysis, we also compared to unvaccinated individuals and to the 2 to 6 day period after a booster dose was received. Analyses were stratified by which primary doses had been received and any mixed primary courses were excluded. Results The relative VE estimate in the 14 days after the BNT162b2 (Comirnaty, Pfizer-BioNTech) booster dose, compared to individuals that received a two-dose primary course, was 87.4 (95% confidence interval 84.9-89.4) in those individuals who received two doses ChAdOx1-S (Vaxzevria, AstraZeneca) as a primary course and 84.4 (95% confidence interval 82.8-85.8) in those individuals who received two doses of BNT162b2 (Comirnaty, Pfizer-BioNTech) as a primary course. Using the 2-6 day period post the booster dose as the baseline gave similar results. The absolute VE from 14 days after the booster, using the unvaccinated baseline, was 93.1(95% confidence interval 91.7-94.3) in those with ChAdOx1-S (Vaxzevria, AstraZeneca) as their primary course and 94.0 (93.4-94.6) for BNT162b2 (Comirnaty, Pfizer-BioNTech) as their primary course. Conclusions Our study provides real world evidence of significant increased protection from the booster vaccine dose against symptomatic disease in those aged over 50 year of age irrespective of which primary course was received.

14.
N Engl J Med ; 385(7): 585-594, 2021 08 12.
Article in English | MEDLINE | ID: covidwho-1319062

ABSTRACT

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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. (Funded by Public Health England.).


Subject(s)
COVID-19 Vaccines/immunology , COVID-19/prevention & control , Immunogenicity, Vaccine , SARS-CoV-2 , Adolescent , Adult , Aged , Aged, 80 and over , COVID-19/epidemiology , COVID-19/virology , Case-Control Studies , Female , Humans , Male , Middle Aged , Treatment Outcome , United Kingdom/epidemiology , Vaccine Potency , Young Adult
15.
Emerg Infect Dis ; 27(7): 1795-1801, 2021 07.
Article in English | MEDLINE | ID: covidwho-1278355

ABSTRACT

We describe results of testing blood donors in London, UK, for severe acute respiratory disease coronavirus 2 (SARS-CoV-2) IgG before and after lockdown measures. Anonymized samples from donors 17-69 years of age were tested using 3 assays: Euroimmun IgG, Abbott IgG, and an immunoglobulin receptor-binding domain assay developed by Public Health England. Seroprevalence increased from 3.0% prelockdown (week 13, beginning March 23, 2020) to 10.4% during lockdown (weeks 15-16) and 12.3% postlockdown (week 18) by the Abbott assay. Estimates were 2.9% prelockdown, 9.9% during lockdown, and 13.0% postlockdown by the Euroimmun assay and 3.5% prelockdown, 11.8% during lockdown, and 14.1% postlockdown by the receptor-binding domain assay. By early May 2020, nearly 1 in 7 donors had evidence of past SARS-CoV-2 infection. Combining results from the Abbott and Euroimmun assays increased seroprevalence by 1.6%, 2.3%, and 0.6% at the 3 timepoints compared with Euroimmun alone, demonstrating the value of using multiple assays.


Subject(s)
COVID-19 , SARS-CoV-2 , Antibodies, Viral , Blood Donors , Communicable Disease Control , England , Humans , Immunoglobulin G , London/epidemiology , Public Health , Sensitivity and Specificity , Seroepidemiologic Studies , United Kingdom
16.
BMJ ; 373: n1088, 2021 05 13.
Article in English | MEDLINE | ID: covidwho-1228861

ABSTRACT

OBJECTIVE: To estimate the real world effectiveness of the Pfizer-BioNTech BNT162b2 and Oxford-AstraZeneca ChAdOx1-S vaccines against confirmed covid-19 symptoms (including the UK variant of concern B.1.1.7), admissions to hospital, and deaths. DESIGN: Test negative case-control study. SETTING: Community testing for covid-19 in England. PARTICIPANTS: 156 930 adults aged 70 years and older who reported symptoms of covid-19 between 8 December 2020 and 19 February 2021 and were successfully linked to vaccination data in the National Immunisation Management System. INTERVENTIONS: Vaccination with BNT162b2 or ChAdOx1-S. MAIN OUTCOME MEASURES: Primary outcomes were polymerase chain reaction confirmed symptomatic SARS-CoV-2 infections, admissions to hospital for covid-19, and deaths with covid-19. RESULTS: Participants aged 80 years and older vaccinated with BNT162b2 before 4 January 2021 had a higher odds of testing positive for covid-19 in the first nine days after vaccination (odds ratio up to 1.48, 95% confidence interval 1.23 to 1.77), indicating that those initially targeted had a higher underlying risk of infection. Vaccine effectiveness was therefore compared with the baseline post-vaccination period. Vaccine effects were noted 10 to 13 days after vaccination, reaching a vaccine effectiveness of 70% (95% confidence interval 59% to 78%), then plateauing. From 14 days after the second dose a vaccination effectiveness of 89% (85% to 93%) was found compared with the increased baseline risk. Participants aged 70 years and older vaccinated from 4 January (when ChAdOx1-S delivery commenced) had a similar underlying risk of covid-19 to unvaccinated individuals. With BNT162b2, vaccine effectiveness reached 61% (51% to 69%) from 28 to 34 days after vaccination, then plateaued. With ChAdOx1-S, effects were seen from 14 to 20 days after vaccination, reaching an effectiveness of 60% (41% to 73%) from 28 to 34 days, increasing to 73% (27% to 90%) from day 35 onwards. On top of the protection against symptomatic disease, a further 43% (33% to 52%) reduced risk of emergency hospital admission and 51% (37% to 62%) reduced risk of death was observed in those who had received one dose of BNT162b2. Participants who had received one dose of ChAdOx1-S had a further 37% (3% to 59%) reduced risk of emergency hospital admission. Follow-up was insufficient to assess the effect of ChAdOx1-S on mortality. Combined with the effect against symptomatic disease, a single dose of either vaccine was about 80% effective at preventing admission to hospital with covid-19 and a single dose of BNT162b2 was 85% effective at preventing death with covid-19. CONCLUSION: Vaccination with either one dose of BNT162b2 or ChAdOx1-S was associated with a significant reduction in symptomatic covid-19 in older adults, and with further protection against severe disease. Both vaccines showed similar effects. Protection was maintained for the duration of follow-up (>6 weeks). A second dose of BNT162b2 was associated with further protection against symptomatic disease. A clear effect of the vaccines against the B.1.1.7 variant was found.


Subject(s)
COVID-19 Vaccines/administration & dosage , COVID-19/prevention & control , Hospitalization/statistics & numerical data , Vaccination/methods , Aged , Aged, 80 and over , COVID-19/diagnosis , COVID-19/immunology , COVID-19/mortality , COVID-19 Testing/methods , COVID-19 Vaccines/immunology , Case-Control Studies , England/epidemiology , Female , Humans , Male , SARS-CoV-2/drug effects , SARS-CoV-2/genetics , SARS-CoV-2/immunology , Treatment Outcome , Vaccination/statistics & numerical data
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