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We investigated a COVID-19 outbreak of the SARS-CoV-2 Delta variant of concern in a London care home, where 8/21 residents and 14/21 staff had received a single dose of Vaxzevria (ChAdOx1-S; AstraZeneca) vaccine. We identified 24 SARS-CoV-2 infections (16 residents, 8 staff) among 40 individuals (19 residents, 21 staff); four (3 residents, 1 staff) were hospitalised, and none died. The attack rate after one vaccine dose was 35.7% (5/14) for staff and 81.3% (13/16) for residents.

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.

Background Strategies to control varicella vary across Europe. Evidence from established programmes has prompted the United Kingdom to re-evaluate the need for universal vaccination. The burden of complicated varicella is a key parameter in the cost-effectiveness analysis. Aim Our objective was to estimate the burden of complicated varicella in England. Methods This electronic health record surveillance study used data from all NHS hospitals in England to identify varicella admissions between 2004 and 2017. The incidence of pre-defined complications of varicella was estimated using ICD-10 codes. Inpatient costs were calculated based on the payment rules for providers of NHS services. Results There were 61,024 admissions with varicella between 2004 and 2017 and 38.1% had a recognised varicella complication. Incidence of hospitalisation increased by 25% and the proportion with complicated varicella by 24% from 2004/05 to 2016/17. The most common complications were bacterial skin infections (11.25%), pneumonia (4.82%), febrile convulsions (3.39%) and encephalitis (2.44%). Complication rates were higher in older age groups and the type of complications more severe. Length of stay for complicated varicella was 3.1 times longer than for uncomplicated varicella and inpatient costs were 72% greater. Conclusion Complicated varicella has a substantial health and economic burden. These data together with data on impact on quality of life are important in informing the cost-effectiveness analysis of universal varicella vaccination.

Interrupted time series (ITS) analysis is a valuable study design for evaluating the effectiveness of population-level health interventions that have been implemented at a clearly defined point in time. It is increasingly being used to evaluate the effectiveness of interventions ranging from clinical therapy to national public health legislation. Whereas the design shares many properties of regression-based approaches in other epidemiological studies, there are a range of unique features of time series data that require additional methodological considerations. In this tutorial we use a worked example to demonstrate a robust approach to ITS analysis using segmented regression. We begin by describing the design and considering when ITS is an appropriate design choice. We then discuss the essential, yet often omitted, step of proposing the impact model a priori. Subsequently, we demonstrate the approach to statistical analysis including the main segmented regression model. Finally we describe the main methodological issues associated with ITS analysis: over-dispersion of time series data, autocorrelation, adjusting for seasonal trends and controlling for time-varying confounders, and we also outline some of the more complex design adaptations that can be used to strengthen the basic ITS design.

Randomized, controlled trials are not always possible to evaluate interventions targeting infectious disease. This is frequently the case when evaluating the population-level impact of vaccines or when evaluating interventions aiming to increase vaccine uptake. Under such circumstances, an array of quasi-experimental designs is increasingly being used to evaluate the effects of vaccines on a wide range of morbidity and health service outcomes. These studies can provide valuable information on the impact of vaccination programs and other related interventions in real-world settings. Nevertheless, not all quasi-experimental designs are equal, and it is important that authors and readers are aware of their relative strengths and potential sources of bias. In this paper, we discuss what a quasi-experimental design is, when they might be used for vaccine evaluation, their strengths and limitations, and examples of their application.

Purpose We examined the association between childhood respiratory infections and adult lung function and how this association varies depending on the age at infection. Methods The Barry Caerphilly Growth study collected information on childhood upper and lower respiratory tract infections (URTI, LRTI) from birth to 5 years on 14 occasions. Subjects were traced prospectively and had lung function measured at age 25 years. Results A total of 581 subjects had acceptable data for both forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). Childhood LRTIs (0–5 years) but not URTIs were negatively associated with all lung function measures except FVC and showed a dose–response effect. In the first year of life, a two-fold increase in the number of LRTIs experienced was associated with a reduction in FEV1 (78 mL; 95% confidence interval [95% CI], 3–153), FEV1/FVC (1.23%; 95% CI 0.25–2.22), forced expiratory flow 25%–75% (0.25 l/sec; 95% CI 0.08–0.41), and peak expiratory flow (0.30 l/sec; 95% CI 0.11–0.49) after adjustment for confounders. Few associations were found after the first year of life. There was evidence that age at infection effect modifies the association between LRTIs and FEV1, forced expiratory flow 25%–75%, and peak expiratory flow. Conclusions LRTIs are associated with an obstructive lung function deficit. Furthermore, the first year of life may be a sensitive period for experiencing LRTIs.

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Any potential economic benefit is likely to be outweighed by the adverse effects on health By 2013 the speed limit on motorways in England and Wales could increase from 70 mph (113 kph) to 80 mph if the coalition government has its way. Its stated aim is to achieve “hundreds of millions of pounds of benefits for the economy,” and it dismisses concerns about health consequences, claiming that advances in car safety have resulted in deaths on British roads falling by more than 75% in the past 55 years and that almost half of all drivers break the current limit anyway.1 Are they right to dismiss these concerns so lightly? The current 70 mph speed limit was trialled in 1965 as a direct response to a series of fatal multiple collisions in fog. Before then speed was unrestricted outside built-up areas. By 1967 the Road Research Laboratory concluded that this restriction had led to a reduction in road fatalities,2 and Barbara Castle—then minister of transport—made it permanent. Since then the number of serious and fatal …

Dear Editor, In their letter, Librero et al. have highlighted one of the main issues affecting studies of the financial crisis (and one that we highlighted ourselves in the ‘Strengths and Limitations’ section of the original article), that is, ‘how do we define the financial crisis?’. As recommended when undertaking interrupted time series analyses of imperfectly identifiable events, we do this as objectively as possible by using an independent indicator—in this case gross domestic product (GDP).1 This is the most commonly used indicator to define a financial crisis; we use it in the same way as in similar studies. There is considerable debate among economists as to how to define a recession, …