Impact of influenza vaccination on respiratory illness rates in children attending private boarding schools in England, 2013-2014: a cohort study.

Several private boarding schools in England have established universal influenza vaccination programmes for their pupils. We evaluated the impact of these programmes on the burden of respiratory illnesses in boarders. Between November 2013 and May 2014, age-specific respiratory disease incidence rates in boarders were compared between schools offering and not offering influenza vaccine to healthy boarders. We adjusted for age, sex, school size and week using negative binomial regression. Forty-three schools comprising 14 776 boarders participated. Almost all boarders (99%) were aged 11-17 years. Nineteen (44%) schools vaccinated healthy boarders against influenza, with a mean uptake of 48·5% (range 14·2-88·5%). Over the study period, 1468 respiratory illnesses were reported in boarders (5·66/1000 boarder-weeks); of these, 33 were influenza-like illnesses (ILIs, 0·26/1000 boarder-weeks) in vaccinating schools and 95 were ILIs (0·74/1000 boarder-weeks) in non-vaccinating schools. The impact of vaccinating healthy boarders was a 54% reduction in ILI in all boarders [rate ratio (RR) 0·46, 95% confidence interval (CI) 0·28-0·76]. Disease rates were also reduced for upper respiratory tract infections (RR 0·72, 95% CI 0·61-0·85) and chest infections (RR 0·18, 95% CI 0·09-0·36). These findings demonstrate a significant impact of influenza vaccination on ILI and other clinical endpoints in secondary-school boarders. Additional research is needed to investigate the impact of influenza vaccination in non-boarding secondary-school settings.

Assessment of baseline age-specific antibody prevalence and incidence of infection to novel influenza A/H1N1 2009.

OBJECTIVES: The objectives of the H1N1 2009 serological surveillance project were twofold: to document (1) the prevalence of cross-reactive antibodies to H1N1 2009 by age group in the population of England prior to arrival of the pandemic strain virus in the UK and (2) the age-specific incidence of infection by month as the pandemic progressed by measuring increases in the proportion of individuals with antibodies to H1N1 2009 by age. METHODS: Residual aliquots of samples submitted to 16 microbiology laboratories in eight regions in England in defined age groups in 2008 and stored by the Health Protection Agency serological surveillance programme were used to document age-stratified prevalence of antibodies to H1N1 2009 prior to the arrival of the pandemic in the UK. Functional antibodies to the H1N1 2009 virus were measured by haemagglutination inhibition (HI) and microneutralisation (MN) assays. For timely measurement of monthly incidence of infection with H1N1 2009 between August 2009 and April 2010, the microbiology serum collections were supplemented by collection of residual sera from chemical pathology laboratories in England. Monthly seroincidence samples were tested by HI only, apart from the final sera collected post pandemic in 2010, which were also tested by MN. Incidence during the pandemic was estimated from changes in prevalence between time points and also by a likelihood-based method. SETTING: Eight regions of England. PARTICIPANTS: Serum samples from patients accessing health care in England from whom blood samples were taken for unrelated microbiological or chemical pathology testing. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Baseline age-specific prevalence of functional antibodies to the H1NI 2009 virus prior to the arrival of the pandemic; changes in antibody prevalence during the period August 2009 to April 2010. RESULTS: Pre-existing cross-reactive antibodies to H1N1 2009 were detected in the baseline sera and increased with age, particularly in those born before 1950. The prediction of immunological protection derived from the baseline serological analysis was consistent with the lower clinical attack rates in older age groups. The high levels of susceptibility in children < 15 years, together with their mixing within school, resulted in the highest attack rates in this age group. Serological analysis by region confirms that there were geographical differences in timing of major pandemic waves. London had a big first wave among the 5- to 14-year age group, with the rest of the country reducing the gap after the second wave. Cumulative incidence in London remained higher throughout the pandemic in each age group. By the end of the second wave it is estimated that as many as 70% of school-aged children in London had been infected. Taken together, these observations are consistent with observations from previous pandemics in 1918, 1957 and 1968 - that the major impact of influenza pandemics is on younger age groups, with a pattern of morbidity and mortality distinct from seasonal influenza epidemics. CONCLUSIONS: Serological analysis of appropriately structured, age-stratified and geographically representative samples can provide an immense amount of information to set in context other measures of pandemic impact in a population, and provide the most accurate measures of population exposure. National scale seroepidemiology studies require cross-agency coordination, multidisciplinary working, and considerable scientific resource. FUNDING: The National Institute for Health Research Health Technology Assessment programme and the Health Protection Agency.

Control of equine influenza: scenario testing using a realistic metapopulation model of spread.

We present a metapopulation model of the spread of equine influenza among thoroughbred horses parametrized with data from a 2003 outbreak in Newmarket, UK. The number of horses initially susceptible is derived from a threshold theorem and a published statistical model. Two simulated likelihood-based methods are used to find the within- and between-yard transmissions using both exponential and empirical latent and infectious periods. We demonstrate that the 2003 outbreak was largely locally driven and use the parametrized model to address important questions of control. The chance of a large epidemic is shown to be largely dependent on the size of the index yard. The impact of poor responders to vaccination is estimated under different scenarios. A small proportion of poor responders strongly influences the efficiency of vaccine policies, which increases risk further when the vaccine and infecting strains differ following antigenic drift. Finally, the use of vaccinating in the face of an outbreak is evaluated at a global and individual management group level. The benefits for an individual horse trainer are found to be substantial, although this is influenced by the behaviour of other trainers.