Methodological challenges in post-licensure vaccine safety studies using large routinely collected datasets

Robust and responsive epidemiological post-licensure vaccine safety studies are the backbone to having confidence in a vaccination programme. Consideration must be given to the unique methodological challenges inherent when assessing a potential causal association between a vaccine and the condition of interest; these can be present from setting up the study through to communicating the results. Public Health England (PHE) has addressed a number of vaccine safety concerns since the 1990’s using routinely collected healthcare data and methods specific to the disease and vaccine under scrutiny. This thesis comprises of seven published post-licensure vaccine safety studies which were carried out in response to a number of different pertinent safety concerns relevant to the UK’s immunisation schedule. As a background to these studies the history of routinely collected data is examined in the context of how we use the data today along with a description of the pre and post-licensure vaccine safety activities which often precede the epidemiological studies. By bringing together the methodological issues of these seven studies and demonstrating the different ways in which these issues have been handled it has created a blueprint for addressing vaccine safety concerns in the future. The seven studies are i) Intussusception and Rotavirus vaccination ii) Narcolepsy in adults and Pandemic Influenza vaccine iii) Convulsions and Pandemic and Seasonal Influenza vaccine iv) Bacterial and Viral Infections and Measles Mumps and Rubella vaccine v) Guillain-Barré syndrome and Seasonal Influenza vaccine vi) Idiopathic Thrombocytopenic Purpura and the second dose of Measles Mumps and Rubella vaccine vii) Bell’s Palsy and Seasonal Influenza vaccine. In conclusion the methodological approaches employed in these studies can be used in the future to assess potential adverse events and the access to routinely collected health data is an essential element of this

No association between atopic outcomes and type of pertussis vaccine given in children born on the Isle of Wight 2001-2002

Clinical Communication

Nephrotic syndrome in infants and toddlers before and after introduction of the meningococcal B vaccine programme in England: An ecological study.

A possible increased risk of nephrotic syndrome (NS) following a meningococal group B vaccination campaign was identified during active safety surveillance in a province in Quebec, Canada where 4 cases were reported from an exposed population of ~490,000, a higher rate than in provinces not using the vaccine. Meningococcal B vaccine has been given routinely at 2, 4 and 12 months of age in the United Kingdom since September 2015. To investigate the Canadian signal we used English hospital admissions data from 2005 to 2019 in 2-23 month old children to determine whether the rate of NS changed following the introduction of the vaccine. The analysis was stratified by age 2-5 months, 6-11 months, 12-17 months and 18-23 months. The results showed no evidence of an increased risk with incidence rate ratios between 0.81 (95% confidence interval 0.56-1.19) for age 6-11 months and 1.18 (0.84-1.66) for age 12-17 months

The risk of non-specific hospitalised infections following MMR vaccination given with and without inactivated vaccines in the second year of life. Comparative self-controlled case-series study in England.

Observational cohort studies in high-income settings have suggested that vaccination order may affect children's subsequent risk of a heterologous infection, with live vaccines reducing and inactivated vaccines (given on their own or with a live vaccine), increasing the risk. We used the self-controlled case-series method, which automatically controls for the individual level confounding to which such cohort studies are prone, to test this hypothesis. We compared the relative incidence (RI) of infections post-vaccination in two calendar periods in England; in Period 1 (September 2002-August 2006) live measles, mumps, rubella (MMR) vaccine was given on its own and in Period 2 (September 2006-April 2010) inactivated vaccines (7-valent pneumococcal conjugate vaccine (PCV7) and sometimes the combined Haemophilus influenzae type b/meningococcal group C vaccine (Hib-MenC)) were given concomitantly with MMR. Admissions for an infection of the upper or lower respiratory tract, gastrointestinal system or other site in children aged 11-23?months were selected from the Hospital Episode Statistics database in England and linked to child health immunisation histories. The analysis included a total of 24,144 infections in 21,067 children in Period 1 and 36,880 in 31,616 children in Period 2. The RI of admission for any infection in Period 1 was 1.00 (95% confidence interval 0.95-1.06) compared with 0.95 (95% confidence interval 0.90-1.00) in Period 2. Comparing the two periods showed no evidence of a difference in the relative incidence estimates with a ratio of RI of 0.94 (95% confidence interval 0.87-1.02), RIs within 90?days of vaccination were 0.94 (0.91-0.97) in Period 1 and 0.94 (0.91-0.97) in Period 2, consistent with a temporary healthy vaccinee effect. In conclusion, we found no evidence to support the hypothesis that there is a reduction in heterologous infections after MMR on its own or an increase after MMR given concomitantly with an inactivated vaccine

Impact of the national rotavirus vaccination programme on acute gastroenteritis in England and associated costs averted.

BACKGROUND: Introduction of infant oral rotavirus vaccination in the UK in July 2013 has resulted in decreased hospitalisations and Emergency Department (ED) visits for acute gastroenteritis (AGE), for both adults and children. We investigated reductions in AGE incidence seen in primary care in the two years after vaccine introduction, and estimated the healthcare costs averted across healthcare settings in the first year of the vaccination programme. METHODS: We used primary care data from the Clinical Practice Research Datalink and age-stratified time-series analyses to derive adjusted incidence rate ratios (IRRa) for AGE in the first two years of the post-vaccination era (July 2013-April 2015) compared to the pre-vaccination era (July 2008-June 2013). We estimated cases averted among children aged <5years in the first year of the vaccination programme by comparing observed numbers of AGE cases in 2013-2014 to numbers predicted from the time-series models. We then estimated the healthcare costs averted for general practice consultations, ED visits and hospitalisations. RESULTS: In general practice, AGE rates in infants (the target group for vaccination) decreased by 15% overall after vaccine introduction (IRRa=0.85; 95%CI=0.76-0.95), and by 41% in the months of historically high rotavirus circulation (IRRa=0.59; 95%CI=0.53-0.66). Rates also decreased in other young children and to a lesser degree in older individuals, indicating herd immunity. Across all three settings (general practice, EDs, and hospitalisations) an estimated 87,376 (95% prediction interval: 62,588-113,561) AGE visits by children aged <5years were averted in 2013-14, associated with an estimated £12.5million (9,209-16,198) reduction in healthcare costs. CONCLUSIONS: The marked decreases in the general practice AGE burden after rotavirus vaccine introduction mirror decreases seen in other UK healthcare settings. Overall, these decreases are associated with substantial averted healthcare costs

Reassessment of the risk of narcolepsy in children in England 8 years after receipt of the AS03-adjuvanted H1N1 pandemic vaccine: A case-coverage study.

BACKGROUND: Early studies of narcolepsy after AS03-adjuvanted pandemic A/H1N12009 vaccine (Pandemrix) could not define the duration of elevated risk post-vaccination nor the risk in children aged under 5 years who may not present until much older. METHODS/FINDINGS: Clinical information and sleep test results, extracted from hospital notes at 3 large pediatric sleep centers in England between September 2017 and June 2018 for narcolepsy cases aged 4-19 years with symptom onset since January 2009, were reviewed by an expert panel to confirm the diagnosis. Vaccination histories were independently obtained from general practitioners (GPs). The odds of vaccination in narcolepsy cases compared with the age-matched English population was calculated after adjustment for clinical conditions that were indications for vaccination. GP questionnaires were returned for 242 of the 244 children with confirmed narcolepsy. Of these 5 were under 5 years, 118 were 5-11 years, and 119 were 12-19 years old at diagnosis; 39 were vaccinated with Pandemrix before onset. The odds ratio (OR) for onset at any time after vaccination was 1.94 (95% confidence interval [CI] 1.30-2.89), The elevated risk period was restricted to onsets within 12 months of vaccination (OR 6.65 [3.44-12.85]) and was highest within the first 6 months. After one year, ORs were not significantly different from 1 up to 8 years after vaccination. The ORs were similar in under five-year-olds and older ages. The estimated attributable risk was 1 in 34,500 doses. Our study is limited by including cases from only 3 sleep centers, who may differ from cases diagnosed in nonparticipating centers, and by imprecision in defining the centers' catchment population. The potential for biased recall of onset shortly after vaccination in cases aware of the association cannot be excluded. CONCLUSIONS: In this study, we found that vaccine-attributable cases have onset of narcolepsy within 12 months of Pandemrix vaccination. The attributable risk is higher than previously estimated in England because of identification of vaccine-attributable cases with late diagnoses. Absence of a compensatory drop in risk 1-8 years after vaccination suggests that Pandemrix does not trigger onsets in those in whom narcolepsy would have occurred later

Studying Trail Enhancement Plans - Health Impact Assessment

This report reflects work on the Studying Trail Enhancement Plans - Health Impact Assessment (STEP-HIA) for the proposed new Cuba Continental Divide National Scenic Trail segment as of April 30, 2015. It is provided to the Santa Fe National Forest and Bureau of Land Management New Mexico for use in preparing an Environmental Impact Assessment and subsequent planning for the proposed project. It was prepared by the University of New Mexico Prevention Research Center and Step Into Cuba Alliance, a partnership of individuals and organizations dedicated to the promotion of walking and hiking for better health in Cuba, NM. In this report, we present information by way of a sequential series of questions that support and lead to predictions and recommendations for the new trail segment

Bias assessment of a test-negative design study of COVID-19 vaccine effectiveness used in national policymaking

National test-negative-case-control (TNCC) studies are used to monitor COVID-19 vaccine effectiveness in the UK. A questionnaire was sent to participants from the first published TNCC COVID-19 vaccine effectiveness study conducted by the UK Health Security Agency, to assess for potential biases and changes in behaviour related to vaccination. The original study included symptomatic adults aged ≥70 years testing for COVID-19 between 08/12/2020 and 21/02/2021. A questionnaire was sent to cases and controls tested from 1-21 February 2021. In this study, 8648 individuals responded to the questionnaire (36.5% response). Using information from the questionnaire to produce a combined estimate that accounted for all potential biases decreased the original vaccine effectiveness estimate after two doses of BNT162b2 from 88% (95% CI: 79-94%) to 85% (95% CI: 68-94%). Self-reported behaviour demonstrated minimal evidence of riskier behaviour after vaccination. These findings offer reassurance to policy makers and clinicians making decisions based on COVID-19 vaccine effectiveness TNCC studies

Evaluating the impact of a continued maternal pertussis immunisation programme in England: A modelling study and cost-effectiveness analysis.

INTRODUCTION: An unexpected resurgence of pertussis cases and infant deaths was observed in some countries that had switched to acellular pertussis vaccines in the primary immunisation schedule. In response to the outbreaks, maternal pertussis vaccination programmes in pregnant women have been adopted worldwide, including the USA in 2011 and the UK in 2012. Following the success of the programme in England, we evaluated the health and economic impact of stopping versus continuing the maternal pertussis immunisation to inform public health policy making. METHODS: We used a mathematical model to estimate the number of infant hospitalisations and deaths related to pertussis in England over 2019-2038. Losses in quality-adjusted life years, QALYs, were considered for infants (aged 0-2 months) who survived or died from pertussis, bereaved parents (of infants who died from pertussis), and women with pertussis (aged 20-44 years). Direct medical costs to the National Health Service included infant hospitalisations, maternal vaccinations, and disease in women. Costs and QALYs were discounted at 3.5%. Changes in the incremental cost-effectiveness ratio, ICER, were explored in sensitivity analyses. RESULTS: The model supports continuing the maternal pertussis immunisation programme as a cost-effective intervention at an ICER of £14,500/QALY (2.5% and 97.5%-quantile: £7,300/QALY to £32,400/QALY). Stopping versus continuing the maternal programme results in an estimated mean of 972 (range 582 to 1489) versus 308 (184 to 471) infant hospitalisations annually. Results were most sensitive to the number of hospitalisations and deaths when stopping the maternal programme. At a cost-effectiveness threshold of £30,000/QALY, the probability of the maternal programme being cost-effective was 96.2%. CONCLUSION: Our findings support continuing the maternal pertussis vaccination programme as otherwise higher levels of disease activity and infant mortality are expected to return. These results have led policy makers to decide to continue the maternal programme in the UK routine immunisation schedule