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1.
Lancet Healthy Longev ; 3(7): e470-e480, 2022 Jul.
Article in English | MEDLINE | ID: covidwho-1915225

ABSTRACT

Background: Residents and staff in long-term care facilities have been prioritised for vaccination against SARS-CoV-2, but data on potential waning of vaccine effectiveness and the effect of booster doses in this vulnerable population are scarce. We aimed to evaluate effectiveness of one, two, and three vaccine doses against infection and severe clinical outcomes in staff and residents of long-term care facilities in England over the first year following vaccine roll-out. Methods: The VIVALDI study is a prospective cohort study done in 331 long-term care facilities in England. Residents aged 65 years or older and staff aged 18 years or older were eligible for participation. Participants had routine PCR testing throughout the study period between Dec 8, 2020, and Dec 11, 2021. We retrieved all PCR results and cycle threshold values for PCR-positive samples from routine testing in long-term care facilities, and positive PCR results from clinical testing in hospitals through the UK's COVID-19 Datastore. PCR results were linked to participants using pseudo-identifiers based on individuals' unique UK National Health Service (NHS) numbers, which were also used to retrieve vaccination records from the National Immunisation Management Service, hospitalisation records from NHS England, and deaths data from the Office for National Statistics through the COVID-19 Datastore. In a Cox proportional hazards regression, we estimated vaccine effectiveness against SARS-CoV-2 infection, COVID-19-related hospitalisation, and COVID-19-related death after one, two, and three vaccine doses, separately by previous SARS-CoV-2 exposure. This study is registered with the ISRCTN Registry, ISRCTN 14447421. Findings: 80 186 residents and staff of long-term care facilities had records available for the study period, of whom 15 518 eligible residents and 19 515 eligible staff were included in the analysis. For residents without evidence of previous SARS-CoV-2 exposure, vaccine effectiveness decreased from 61·7% (95% CI 35·1 to 77·4) to 22·0% (-14·9 to 47·0) against infection; from 89·0% (70·6 to 95·9) to 56·3% (30·1 to 72·6) against hospitalisation; and from 96·4% (84·3 to 99·2) to 64·4% (36·1 to 80·1) against death, when comparing 14-83 days after dose two and 84 days or more after dose two. For staff without evidence of previous exposure, vaccine effectiveness against infection decreased slightly from 57·9% (43·1 to 68·9) at 14-83 days after dose two to 42·1% (29·9 to 52·2) at 84 days or more after dose two. There were no hospitalisations or deaths among unexposed staff at 14-83 days, but seven hospitalisations (vaccine effectiveness 91·0% [95% CI 74·3 to 96·8]) and one death were observed at 84 days or more after dose two. High vaccine effectiveness was restored following a third vaccine dose, with vaccine effectiveness in unexposed residents of 72·7% (55·8 to 83·1) against infection, 90·1% (80·6 to 95·0) against hospitalisation, and 97·5% (88·1 to 99·5) against death; and vaccine effectiveness in unexposed staff of 78·2% (70·0 to 84·1) against infection and 95·8% (49·9 to 99·6) against hospitalisation. There were no COVID-19-related deaths among unexposed staff after the third vaccine dose. Interpretation: Our findings showed substantial waning of SARS-CoV-2 vaccine effectiveness against all outcomes in residents of long-term care facilities from 12 weeks after a primary course of ChAdOx1-S or mRNA vaccines. Boosters restored protection, and maximised immunity across all outcomes. These findings show the importance of boosting and the need for ongoing surveillance in this vulnerable cohort. Funding: UK Government Department of Health and Social Care.

2.
J Infect Dis ; 2022 Apr 16.
Article in English | MEDLINE | ID: covidwho-1883018

ABSTRACT

General population studies have shown strong humoral response following SARS-CoV-2 vaccination with subsequent waning of anti-spike antibody levels. Vaccine-induced immune responses are often attenuated in frail and older populations, but published data are scarce. We measured SARS-CoV-2 anti-spike antibody levels in Long-Term Care Facility residents and staff following second vaccination dose with Oxford-AstraZeneca or Pfizer-BioNTech. Vaccination elicited robust antibody responses in older residents, suggesting comparable levels of vaccine-induced immunity to that in the general population. Antibody levels are higher after Pfizer-BioNTech vaccination but fall more rapidly compared to Oxford-AstraZeneca recipients and are enhanced by prior infection in both groups.

3.
Lancet Healthy Longev ; 3(5): e347-e355, 2022 May.
Article in English | MEDLINE | ID: covidwho-1821559

ABSTRACT

Background: The SARS-CoV-2 omicron variant (B.1.1.529) is highly transmissible, but disease severity appears to be reduced compared with previous variants such as alpha and delta. We investigated the risk of severe outcomes following infection in residents of long-term care facilities. Methods: We did a prospective cohort study in residents of long-term care facilities in England who were tested regularly for SARS-CoV-2 between Sept 1, 2021, and Feb 1, 2022, and who were participants of the VIVALDI study. Residents were eligible for inclusion if they had a positive PCR or lateral flow device test during the study period, which could be linked to a National Health Service (NHS) number, enabling linkage to hospital admissions and mortality datasets. PCR or lateral flow device test results were linked to national hospital admission and mortality records using the NHS-number-based pseudo-identifier. We compared the risk of hospital admission (within 14 days following a positive SARS-CoV-2 test) or death (within 28 days) in residents who had tested positive for SARS-CoV-2 in the period shortly before omicron emerged (delta-dominant) and in the omicron-dominant period, adjusting for age, sex, primary vaccine course, past infection, and booster vaccination. Variants were confirmed by sequencing or spike-gene status in a subset of samples. Results: 795 233 tests were done in 333 long-term care facilities, of which 159 084 (20·0%) could not be linked to a pseudo-identifier and 138 012 (17·4%) were done in residents. Eight residents had two episodes of infection (>28 days apart) and in these cases the second episode was excluded from the analysis. 2264 residents in 259 long-term care facilities (median age 84·5 years, IQR 77·9-90·0) were diagnosed with SARS-CoV-2, of whom 253 (11·2%) had a previous infection and 1468 (64·8%) had received a booster vaccination. About a third of participants were male. Risk of hospital admissions was markedly lower in the 1864 residents infected in the omicron-period (4·51%, 95% CI 3·65-5·55) than in the 400 residents infected in the pre-omicron period (10·50%, 7·87-13·94), as was risk of death (5·48% [4·52-6·64] vs 10·75% [8·09-14·22]). Adjusted hazard ratios (aHR) also indicated a reduction in hospital admissions (0·64, 95% CI 0·41-1·00; p=0·051) and mortality (aHR 0·68, 0·44-1·04; p=0·076) in the omicron versus the pre-omicron period. Findings were similar in residents with a confirmed variant. Interpretation: Observed reduced severity of the omicron variant compared with previous variants suggests that the wave of omicron infections is unlikely to lead to a major surge in severe disease in long-term care facility populations with high levels of vaccine coverage or natural immunity. Continued surveillance in this vulnerable population is important to protect residents from infection and monitor the public health effect of emerging variants. Funding: UK Department of Health and Social Care.

4.
EuropePMC; 2022.
Preprint in English | EuropePMC | ID: ppcovidwho-330319

ABSTRACT

Background Long-term care facilities (LTCF) have been prioritised for vaccination, but data on potential waning of vaccine effectiveness (VE) and the impact of booster doses in this vulnerable population remains scarce. Methods We included residents and staff from 331 LTCFs enrolled in VIVALDI ( ISRCTN 14447421 ), who underwent routine PCR testing between Dec 8, 2020 - Dec 11, 2021 in a Cox proportional hazards regression, estimating VE against SARS-CoV2 infection, COVID-19-related hospitalisation, and COVID-19-related death after 1-3 vaccine doses, stratifying by previous SARS-CoV2 exposure. Results For 15,518 older residents, VE declined from 50·7% (15·5, 71·3) to 17·2% (∼23·9, 44·6) against infection;from 85·4% (60·7, 94·.6) to 54·3% (26·2, 71·7) against hospitalisation;and from 94·4% (76·4, 98·7) to 62·8% (32·9, 79·4) against death, when comparing 2-12 weeks and ≥12 weeks after two doses. For 19,515 staff, VE against infection declined slightly from 50·3% (32·7, 63·3) to 42·1% 29·5, 52·4). High VE was restored following a third dose, with VE of 71·6% (53·5, 82·7) and 78·3% (70·1, 84·3) against infection and 89·9% (80·0, 94·6) and 95·8% (50·4, 99·6) against hospitalisation, for residents and staff respectively;and 97·5% (88·1, 99·5) against death for residents. Interpretation Substantial waning of VE is observed against all outcomes in residents from 12 weeks after a primary course of AstraZeneca or mRNA vaccines. Boosters restore protection, and maximise immunity across all outcomes. These findings demonstrate the importance of boosting and the need for ongoing surveillance of VE in this vulnerable cohort. Funding UK Government Department of Health and Social Care. Research in Context Evidence before this study We searched MEDLINE and medRxiv for studies reporting vaccine effectiveness (VE) over time after two or three doses against SARS-CoV2 infection, COVID-19-related hospitalisation, or COVID-19-related death amongst staff or residents of long-term care facilities (LTCFs), that were published between Jan 1, 2020, and December 21, 2021. We used variations of the search terms “COVID-19” OR “SARS-CoV-2” AND “vaccine effectiveness” OR “vaccine efficacy” AND “care homes” OR “long term care facilities”. We identified 8 articles reporting two-dose data from LTCFs, including 1 peer-reviewed paper from Israel, 1 preprint from Denmark, 1 preprint from Norway, 1 peer-reviewed paper from France, two peer-reviewed papers from Spain, 1 peer-reviewed paper from the USA, and 1 preprint from England;however none of these studies examined waning of protection over time after two doses. Five studies (mRNA vaccines 3-4 weeks interval) reported short-term two-dose VE of 49-71% in residents, and 82-90% in staff. Two-dose VE was reported to be 75-88% against hospitalisation, 87-97% against death, and 86% against either outcome. An English study of residents (Pfizer or AstraZeneca, 8-12 week interval) reported 73% VE against infection and noted VE waning from 7 weeks after the first dose, but did not examine waning after the second dose. All of these studies were set prior to emergence of the Delta variant and did not examine waning of immunity due to short lengths of follow-up after Dose 2. Only one study (USA) compared Pfizer/Moderna two-dose VE against infection in LTCF residents before (67·5% [60·1-73·5%]) and during (53·1% [49·1-56·7%]) Delta variant predominance;however, authors could not access vaccination dates therefore did not account for any waning of immunity over time;they also did not examine any severe clinical outcomes. We identified only one correspondence piece from Israel (Pfizer 3-4 week interval) describing the benefit of a third ‘booster’ dose in LTCFs;it reported relative rate reductions of 71% for infection and 80%, for hospitalisation in the period after booster roll-out. However, individual-level VE estimates by time since vaccination were not reported, and adju tment for prior infection was not undertaken. Overall, there was a paucity of data on non-mRNA vaccines, waning of immunity over time after two doses, and VE following a third (booster) dose in LTCF populations, which we address in this study. Added value of this study We report findings from a prospective cohort study that includes 15,518 residents and 19,515 staff from 331 LTCFs across England, who underwent routine PCR testing 2-3 times per month, looking at SARS-CoV2 vaccine effectiveness over 12 months (Dec 8, 2020-Dec 11, 2021), which is the longest duration of follow-up of any study within this vulnerable cohort. We evaluated the effectiveness of first, second, and booster vaccine doses of AstraZeneca, Pfizer, and Moderna against infection, hospitalisation, and death over the 12 months when the Alpha and Delta variants were dominant. Our findings affirm that complete vaccination with two doses of AstraZeneca or mRNA vaccines offers moderate protection against infection, and high protection against severe clinical outcomes, however this protection declines over time, particularly for residents. A third booster dose of an mRNA vaccine restores, and indeed maximises, VE to 71·6% (53·5, 82·7) and 78·3% (70·1, 84·3) against infection, and 89·9% (80·0, 94·6) and 95·8% (50·4, 99·6) against hospitalisation, for residents and staff respectively, and to 97·5% (88·1, 99·5) against death for residents, with similar protection offered after the third dose irrespective of primary course type. This is the first study to examine and describe waning of immunity over a one-year period, as well as vaccine effectiveness of a booster dose, in a large cohort of LTCF staff and residents. Implications of all the available evidence Taken together, our findings indicate high short-term immunity against SARS-CoV2 infection and very high immunity against severe clinical outcomes of COVID-19 for LTCF residents and staff following vaccination. However substantial waning in vaccine-derived immunity is seen beyond 3 months, irrespective of vaccine type, suggesting the need for regular boosting to maintain protection in this vulnerable cohort. Although this analysis took place in the pre-Omicron period, these trends of waning immunity over time are likely to be generalisable across variants, carrying important implications for long-term vaccination policy in LTCFs. Ongoing surveillance in this vulnerable cohort remains crucial, in order to describe further changes in vaccine-induced immunity, particularly in the context of new variants.

5.
EuropePMC;
Preprint in English | EuropePMC | ID: ppcovidwho-327186

ABSTRACT

Background General population studies have shown strong humoral response following SARS-CoV-2 vaccination with subsequent waning of anti-spike antibody levels. Vaccine-induced immune responses are often attenuated in frail and older populations such as Long-Term Care Facility (LTCF) residents but published data are scarce. Methods VIVALDI is a prospective cohort study in England which links serial blood sampling in LTCF staff and residents to routine healthcare records. We measured quantitative titres of SARS-CoV-2 anti-spike antibodies in residents and staff following second vaccination dose with ChAdOx1 nCov-19 (Oxford-AstraZeneca) or BNT162b2 (Pfizer-BioNTech). We investigated differences in peak antibody levels and rates of decline using linear mixed effects models. Results We report on 1317 samples from 402 residents (median age 86 years, IQR 78-91) and 632 staff (50 years, 37-58), ≤280 days from second vaccination dose. Peak antibody titres were 7.9-fold higher after Pfizer-BioNTech vaccine compared to Oxford-AstraZeneca (95%CI 3.6-17.0;P <0.01) but rate of decline was increased, and titres were similar at 6 months. Prior infection was associated with higher peak antibody levels in both Pfizer-BioNTech (2.8-fold, 1.9-4.1;P <0.01) and Oxford-AstraZeneca (4.8-fold, 3.2-7.1;P <0.01) recipients and slower rates of antibody decline. Increasing age was associated with a modest reduction in peak antibody levels for Oxford-AstraZeneca recipients. Conclusions Double-dose vaccination elicits robust and stable antibody responses in older LTCF residents, suggesting comparable levels of vaccine-induced immunity to that in the general population. Antibody levels are higher after Pfizer-BioNTech vaccination but fall more rapidly compared to Oxford-AstraZeneca recipients and are enhanced by prior infection in both groups.

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