Non-specific effects of MMR vaccines on infectious disease related hospitalizations during the second year of life in high-income countries: a systematic review and meta-analysis

Measles, mumps, and rubella vaccine at age 6 months and hospitalisation for infection before age 12 months: randomised controlled trial

OBJECTIVE

To test for potential non-specific effects of an additional, early measles, mumps, and rubella (MMR) vaccine at age 5-7 months on risk of infection related hospitalisation before age 12 months.

DESIGN

Randomised, double blinded, placebo controlled trial.

SETTING

Denmark, a high income setting with low exposure to MMR.

PARTICIPANTS

6540 Danish infants aged 5 to 7 months.

INTERVENTIONS

Infants were randomly allocated 1:1 to intramuscular injection with standard titre MMR vaccine (M-M-R VaxPro) or placebo (solvent only).

MAIN OUTCOME MEASURES

Hospitalisations for infection, defined as all hospital contacts of infants referred from primary care for hospital evaluation and with an infection diagnosed, analysed as recurrent events, from randomisation to 12 months of age. In secondary analyses implications of censoring for date of subsequent diphtheria, tetanus, pertussis, polio, Haemophilus influenzae type B, and immunisation with pneumococci conjugate vaccine (DTaP-IPV-Hib+PCV), potential effect modification by sex, prematurity (<37 weeks' gestation), season, and age at randomisation were tested, and the secondary outcomes of hospitalisations ≥12 hours and antibiotic use were evaluated.

RESULTS

6536 infants were included in the intention-to-treat analysis. 3264 infants randomised to MMR vaccine experienced 786 hospitalisations for infection before age 12 months compared with 762 for the 3272 infants randomised to placebo. In the intention-to-treat analysis the rate of hospitalisations for infection did not differ between the MMR vaccine and placebo groups (hazard ratio 1.03, 95% confidence interval 0.91 to 1.18). For infants randomised to MMR vaccine compared with those randomised to placebo, the hazard ratio of hospitalisations for infection with a duration of at least 12 hours was 1.25 (0.88 to 1.77), and for prescriptions of antibiotics was 1.04 (0.88 to 1.23). No significant effect modifications were found by sex, prematurity, age at randomisation, or season. The estimate did not change when censoring at the date infants received DTaP-IPV-Hib+PCV after randomisation (1.02, 0.90 to 1.16).

CONCLUSION

Findings of this trial conducted in Denmark, a high income setting, do not support the hypothesis that live attenuated MMR vaccine administered early to infants aged 5-7 months decreases the rate of hospitalisations for non-targeted infection before age 12 months.

TRIAL REGISTRATION

EU Clinical Trials Registry EudraCT 2016-001901-18 and ClinicalTrials.gov NCT03780179.

Cohort Profile: Childhood morbidity and potential non-specific effects of the childhood vaccination programmes in the Nordic countries (NONSEnse): register-based cohort of children born 1990-2017/2018

PURPOSE

The aim of the NONSEnse project is to investigate the non-specific effects of vaccines and immunisation programmes on the overall health of children by using information from the extensive nationwide registers on health and sociodemographic factors in Denmark, Finland, Norway and Sweden.

PARTICIPANTS

The cohort covers 9 072 420 children aged 0-17 years, born 1990-2017/2018 and living in Denmark, Finland, Norway or Sweden. All countries use a unique identification number for its permanent residents, which makes it possible to link individual-level information from different registers.

FINDINGS TO DATE

Data collection and harmonisation according to a common data model was completed in March 2022. As a prerequisite for comparing the effects of childhood vaccinations on the overall health of children across the Nordic countries, we have identified indicators measuring similar levels of infectious disease morbidity across these settings. So far, studies pertaining to non-specific effects of vaccines are limited to investigations that could be undertaken using aggregated data sets that were available before the NONSEnse cohort with individual-level information was completely set up.

FUTURE PLANS

We are currently performing several studies of the effects on non-targeted infectious disease morbidity across the countries following vaccination against measles, mumps, rubella, diphtheria, tetanus, pertussis, human papillomavirus, rotavirus and influenza. Multiple studies are planned within the next years using different study designs to facilitate triangulation of results and enhance causal inference.

REGISTRATION

No clinical trials will be conducted within the NONSEnse project.

Effect of MMR Vaccination to Mitigate Severe Sequelae Associated With COVID-19: Challenges and Lessons Learned

Mortality in COVID-19 cases was strongly associated with progressive lung inflammation and eventual sepsis. There is mounting evidence that live attenuated vaccines commonly administered during childhood, also provide beneficial non-specific immune effects, including reduced mortality and hospitalization due to unrelated infections. It has been proposed that live attenuated vaccine-associated non-specific effects are a result of inducing trained innate immunity to function more effectively against broader infections. In support of this, our laboratory has reported that immunization with a live attenuated fungal strain induces a novel form of trained innate immunity which provides protection against various inducers of sepsis in mice via myeloid-derived suppressor cells. Accordingly, we initiated a randomized control clinical trial with the live attenuated Measles, Mumps, Rubella (MMR) vaccine in healthcare workers in the greater New Orleans area aimed at preventing/reducing severe lung inflammation/sepsis associated with COVID-19 (ClinicalTrials.gov Identifier: NCT04475081). Included was an outcome to evaluate the myeloid-derived suppressor cell populations in blood between those administered the MMR vaccine vs placebo. The unanticipated emergency approval of several COVID-19 vaccines in the midst of the MMR clinical trials eliminated the ability to examine effects of the MMR vaccine on COVID-19-related health status. Unfortunately, we were also unable to show any impact of the MMR vaccine on peripheral blood myeloid-derived suppressor cells due to several inherent limitations (low percentages of blood leukocytes, small sample size), that also included a collaboration with a similar trial (CROWN CORONATION; ClinicalTrials.gov Identifier: NCT04333732) in St. Louis, MO. In contrast, monitoring the COVID-19 vaccine response in trial participants revealed that high COVID-19 antibody titers occurred more often in those who received the MMR vaccine vs placebo. While the trial was largely inconclusive, lessons learned from addressing several trial-associated challenges may aid future studies that test the non-specific beneficial immune effects of live attenuated vaccines.

Impact of industry sponsorship on the quality of systematic reviews of vaccines: a cross-sectional analysis of studies published from 2016 to 2019

BACKGROUND

Systematic reviews (SRs) provide the highest level of evidence and inform evidence-based decision making in health care. Earlier studies found association with industry to be negatively associated with methodological quality of SRs. However, this has not been investigated in SRs on vaccines.

METHODS

We performed a systematic literature search using MEDLINE and EMBASE in March 2020. The results were restricted to those published between 2016 and 2019 with no language restrictions. Study characteristics were extracted by one person and checked by an experienced reviewer. The methodological quality of the SRs was assessed with the AMSTAR 2 tool by multiple reviewers after a calibration exercise was performed. A summary score for each SR was calculated. The Mann-Whitney U test and Fisher's exact test were performed to compare both groups.

RESULTS

Out of 185 SRs that met all inclusion criteria, 27 SRs were industry funded. Those were matched with 30 non-industry funded SRs resulting in a total sample size of 57. The mean AMSTAR 2 summary score across all SRs was 0.49. Overall, the median AMSTAR 2 summary score was higher for the non-industry funded SRs than for the industry-funded SRs (0.62 vs. 0.36; p < .00001). Lower ratings for industry funded SRs were consistent across all but one AMSTAR 2 item, though significantly lower only for three specific items.

CONCLUSION

The methodological quality of SRs in vaccination is comparable to SRs in other fields, while it is still suboptimal. We are not able to provide a satisfactory explanation why industry funded SRs had a lower methodological quality than non-industry funded SRs over recent years. Industry funding is an important indicator of methodological quality for vaccine SRs and should be carefully considered when appraising SR quality.

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.

Oral Polio Vaccine to Protect Against COVID-19: Out of the Box Strategies?

The global coronavirus disease 2019 pandemic has raised significant concerns of developing rapid, broad strategies to protect the vulnerable population and prevent morbidity and mortality. However, even with an aggressive approach, controlling the pandemic has been challenging, with concerns of emerging variants that likely escape vaccines, nonadherence of social distancing/preventive measures by the public, and challenges in rapid implementation of a global vaccination program that involves mass production, distribution, and execution. In this review, we revisit the utilization of attenuated vaccinations, such as the oral polio vaccine, which are safe, easy to administer, and likely provide cross-protection against respiratory pathogens. We discuss the rationale and data supporting its use and detail description of available vaccines that could be repurposed for curtailing the pandemic.

Revaccination with measles-mumps-rubella vaccine and hospitalization for infection in Denmark and Sweden - An interrupted time-series analysis

BACKGROUND

In a previous cohort study of 4-year-old Danish children, revaccination with the live measles-mumps-rubella vaccine (MMR) was associated with a 16% reduction in the rate of hospitalization lasting two days or longer for non-measles-mumps-rubella infections.

AIM

To examine if the introduction of revaccination with MMR at 4 years of age in Denmark (spring 2008) and at 7-9 years of age in Sweden (autumn 2009), at a time when there was virtually no measles, mumps or rubella cases, was associated with a reduction in the rate of hospitalization-for-infection lasting two days or longer at the population level.

METHODS

We included 4-year-olds in Denmark and 7-9-year-olds in Sweden. We obtained the number of hospitalization-for-infection lasting two days or longer from nationwide hospital registers. Person-years at risk were approximated from population statistics for each season and year. We performed an interrupted time series analysis using Poisson regression to estimate the change in hospitalization incidence rates following the introduction of MMR revaccination, adjusting for seasonality. We also performed analyses with control series (3-year-olds in Denmark and 4-year-olds in Sweden).

RESULTS

Comparing the incidence of hospitalization-for-infection lasting two days or longer after the introduction of MMR revaccination with the expected level without an introduction of MMR revaccination resulted in an incidence rate ratio of 1.07 (95% confidence interval [CI] = 0.89-1.28) for 4-year-olds in Denmark and 0.89 (95% CI = 0.77-1.02) for 7-9-year-olds in Sweden in analyses without controls. Analyses with controls gave similar results.

CONCLUSION

This population-level study of the introduction of MMR revaccination in Denmark and Sweden had inadequate power to confirm or refute the findings from an individual-level Danish study of an association between MMR revaccination and a lower incidence rate of hospitalization-for-infection lasting two days or longer.

A new perspective for mitigation of SARS-CoV-2 infection: priming the innate immune system for viral attack

The course of infection by SARS-CoV-2 frequently includes a long asymptomatic period, followed in some individuals by an immune dysregulation period that may lead to complications and immunopathology-induced death. This course of disease suggests that the virus often evades detection by the innate immune system. We suggest a novel therapeutic approach to mitigate the infection's severity, probability of complications and duration. We propose that priming an individual's innate immune system for viral attack shortly before it is expected to occur may allow pre-activation of the preferable trajectory of immune response, leading to early detection of the virus. Priming can be carried out, for example, by administering a standard vaccine or another reagent that elicits a broad anti-viral innate immune response. By the time that the expected SARS-CoV-2 infection occurs, activation cascades will have been put in motion and levels of immune factors needed to combat the infection will have been elevated. The infection would thus be cleared faster and with less complication than otherwise, alleviating adverse clinical outcomes at the individual level. Moreover, priming may also mitigate population-level risk by reducing need for hospitalizations and decreasing the infectious period of individuals, thus slowing the spread and reducing the impact of the epidemic. In view of the latter consideration, our proposal may have a significant epidemiological impact even if applied primarily to low-risk individuals, such as young adults, who often show mild symptoms or none, by shortening the period during which they unknowingly infect others. The proposed view is, at this time, an unproven hypothesis. Although supported by robust bio-medical reasoning and multiple lines of evidence, carefully designed clinical trials are necessary.