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

Is vaccination against measles, mumps, and rubella associated with reduced rates of antibiotic treatments among children below the age of 2 years? Nationwide register-based study from Denmark, Finland, Norway, and Sweden

OBJECTIVES

Previous studies have shown that vaccination against measles, mumps, and rubella (MMR) may have beneficial non-specific effects, reducing the risk of infections not targeted by the vaccine. We investigated if MMR vaccine given after the third dose of diphtheria-tetanus-acellular pertussis vaccine (DTaP3), was associated with reduced rates of antibiotic treatments.

METHODS

Register-based cohort study following children from the age of recommended MMR vaccination until age 2 years. We included 831,287 children born in Denmark, Finland, Norway, and Sweden who had received DTaP3 but not yet MMR vaccine. Cox proportional hazards regression with age as the underlying timescale and vaccination status as a time-varying exposure was used to estimate covariate-adjusted Hazard Ratios (aHRs) and inverse probability of treatment weighted (IPTW) HRs of antibiotic treatments. Summary estimates were calculated using random-effects meta-analysis.

RESULTS

Compared with only having received DTaP3, receipt of MMR vaccine after DTaP3 was associated with reduced rates of antibiotic treatments in all countries: the aHR was 0.92 (0.91-0.93) in Denmark, 0.92 (0.90-0.94) in Finland, 0.84 (0.82-0.85) in Norway, and 0.87 (0.85-0.90) in Sweden, yielding a summary estimate of 0.89 (0.85-0.93). A stronger beneficial association was seen in a negative control exposure analysis comparing children vaccinated with DTaP3 vs two doses of DTaP.

CONCLUSIONS

Across the Nordic countries, receipt of MMR vaccine after DTaP3 was associated with an 11% lower rate of antibiotic treatments. The negative control analysis suggests that the findings are affected by residual confounding. Findings suggest that potential non-specific effects of MMR vaccine are of limited clinical and public health importance for the milder infections treated out-of-hospital in the Nordic setting.

A retrospective nationwide register-based study to evaluate the non-specific effects of first MMR vaccination among children in Finland

BACKGROUND

According to earlier studies, live vaccines like measles-mumps-rubella (MMR) vaccine could reduce also other infections than only the infections they are targeted against. This non-specific effect has been seen especially in studies in low-income countries and results from high-income countries have not been unambiguous. In 2011 Finland changed the recommended schedule for the first MMR vaccination from 18 months to 12 months of age. This change created a natural experiment for evaluating the potential non-specific effects.

METHODS

This is a retrospective nationwide register-based cohort study of Finnish children born between 2008 and 2012. Children were divided into two cohorts by age at MMR vaccination: children administered early MMR vaccination (11 through 12 months of age) and late MMR vaccination (18 through 19 months of age). Morbidity was evaluated during the main follow-up period (from 13 to 17 months of age) and before any MMR vaccination (3 to 10 months) and after all were vaccinated with MMR (20 to 35 months) as control follow-up periods. We analyzed all infections and did additional analyzes for urinary tract infections (UTI) and bronchitis. Injuries were analyzed as a control outcome.

RESULTS

Early MMR vaccinated children (N = 79949) had fewer infections compared to late MMR vaccinated (N = 60965) during the main follow-up period. The incidence rate ratio (IRR) was 0.84 (95 % confidence interval (95 % CI) 0.81-0.87). However, similar differences were also observed during the control follow-up periods. MMR vaccinated children had less UTI in the main follow-up period (IRR 0.73, 0.60-0.89) but not in the control follow-up periods. When stratified by sex, the difference was observed among girls but not in boys.

CONCLUSION

No clear evidence was found for non-specific effects in infectious diseases morbidity. However, there could be a nonspecific effect on UTI. Confirmation is needed from other studies, especially from high-income countries.

Health economic analyses of secondary vaccine effects: a systematic review and policy insights

INTRODUCTION

: Numerous analyses demonstrate substantial health economic impacts of primary vaccine effects (preventing or mitigating clinical manifestations of the diseases they target), but vaccines may also be associated with secondary effects, previously known as non-specific, heterologous, or off-target effects.

AREAS COVERED

: We define key concepts to distinguish primary and secondary vaccine effects for health economic analyses, summarized terminology used in different fields, and perform a systematic review of health economic analyses focused on secondary vaccine effects (SVEs).

EXPERT OPINION

: Health economists integrate evidence from multiple fields, which often use incomplete or inconsistent definitions. Like regulators and policy makers, health economists require high-quality evidence of specific effects. Consistent with the limited evidence on mechanisms of action for SVEs, the associated health economic literature remains highly limited, with 4 studies identified by our systematic review. The lack of specific and well-controlled evidence that supports quantification of specific SVEs limits the consideration of these effects in vaccine research, development, regulatory, and recommendation decisions and health economic analyses.

A narrative review of nonspecific effects of pediatric vaccines on child mortality and morbidity

We reviewed evidence on nonspecific effects of pediatric vaccines on mortality and morbidity in countries with high child mortality. Literature search of epidemiological studies was conducted for studies published between 2000 and September 2021 using MEDLINE. Consistent evidence exists regarding the potential protective effect of measles vaccine on child survival. Vaccination with Bacillus Calmette-Guérin (BCG) vaccine was related to lower risk of mortality in young children (including low birth weight babies) and inverse associations were found between developing a scar and having a positive tuberculin test after BCG vaccination with mortality. BCG vaccine might also reduce the risk of nontuberculosis infectious diseases. Studies on the association between diphtheria-pertussis-tetanus (DPT) vaccine and child survival showed inconsistent findings, which might be affected by bias and confounding. More evidence is needed to assess the role of these and other vaccines in children's health and to better understand potential biological mechanisms and other influential factors.

Quadrivalent human papillomavirus vaccination and non-targeted infectious disease hospitalisation: Population-based self-controlled case series analysis

Background

Claims of non-live vaccines having deleterious effects on non-targeted infectious disease and mortality among females persists. The majority of the available evidence is from West Africa and consists of observational studies and the interpretation and implications are controversial. Results from high-income countries have been conflicting. We evaluated the association between a human papillomavirus vaccine, a non-live vaccine primarily administered to pre-adolescent females, and non-targeted infectious disease in a high-income country.

Methods

We constructed a nationwide cohort of all Danish females 10 to 29 years of age during 2007 to 2016 with information on quadrivalent human papillomavirus vaccination status and infectious disease hospital contacts using national registers. Nested in this cohort, we conducted a self-controlled case series (SCCS) analysis comparing the rates of hospitalisation in a 90-day main risk period following the latest vaccination to reference period rates with adjustment for age and season.

Findings

We included 853,879 Danish-born females aged 10 to 29 years of age during the 2007 to 2016 study period in the study cohort. We identified a total of 65,293 infectious disease hospitalisations among 50,599 participants; 46,955 cases among 37,003 participants vaccinated during follow-up were included in the SCCS analysis. There was no statistically significantly increased risk of infectious disease hospitalisation in the 90-day main risk period (rate ratio 0.92, 95% CI 0.88 to 0.95).

Interpretation

Reassuringly, our large well-controlled study does not support that human papillomavirus vaccination increases the risk of non-targeted infectious disease in any clinically meaningful way. While our study does not provide evidence against adverse effects of other non-live vaccines, it does provide evidence against the claim that all non-live vaccines increase risk of heterologous infections in females.

Funding

The study was supported by the Novo Nordisk Foundation.

Vaccine safety issues at the turn of the 21st century

Global gains in vaccination coverage during the early 21st century have been threatened by the emergence of antivaccination groups that have questioned the effectiveness of vaccines to generate public distrust of vaccines and immunisation programmes. This manuscript summarises six key topics that have been at the centre of global discussions on vaccine safety during the early 21st century: thiomersal in multi-dose non-live vaccines, aluminium adjuvants used with several non-live vaccines, autism and auto-immune conditions as possible consequences of vaccination, a risk of immune overload with increasing numbers of vaccinations, and detrimental non-specific effects (NSEs) of vaccination. For each topic, we describe the hypothesis behind the public concern, the evidence reviewed by the WHO’s Global Advisory Committee for Vaccine Safety (GACVS) during 1999–2019, and any significant new data that has emerged since GACVS conclusions were made. Although the scientific evidence on these issues overwhelmingly supports the safety of vaccines, communication messages to caregivers and providers need to condense and convey scientific information in an appropriate way to address concerns contributing to vaccine distrust. In addition, there is need for further studies specifically designed to address both positive and negative NSE of vaccination. The role of GACVS will be increasingly important in evaluating the evidence and engaging the global community in promoting and assuring the safety of vaccines in the decades to come as we move into an era in which we use new vaccination platforms, antigens and formulations.

The risk of Kawasaki disease after pneumococcal conjugate & meningococcal B vaccine in England: A self-controlled case-series analysis

Kawasaki disease (KD) is an uncommon condition occasionally reported after childhood vaccination. Admissions with a KD-compatible diagnosis identified from a national database in England were linked to immunisation records to investigate the risk after pneumococcal conjugate (PCV) or meningococcal B (MenB) vaccines. Both are given at 2/4/12 months of age but were introduced sequentially, allowing their effects to be separately assessed. A total of 553 linked admissions in 512 individuals were validated as KD. The relative incidence (RI) within 28 days of PCV doses 1 or 2 measured by the self-controlled case-series method was 0.62 (95% confidence interval (CI) 0.38-1.00) with a significantly decreased risk after dose 3 (RI 0.30 (95% CI 0.11-0.77)). For MenB vaccine, the RI after doses 1 or 2 was 1.03 (95% CI 0.51-2.05) and 0.64 (95% CI 0.08-5.26) after dose 3. This study shows no evidence of an increased risk of KD after either vaccine.