Editorials
Infectious diseases Environmental health
Volume 207 - Issue 9

Trends in meningococcal disease: challenges for vaccine control when disease is rare

Authors:  Andrew J Pollard and Hannah Christensen

Med J Aust 2017; 207 (9): 380-381. || doi: 10.5694/mja17.00514
Published online: 6 November 2017

The clinical, social and economic value of vaccination varies both with time and by population group

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The clinical, social and economic value of vaccination varies both with time and by population group

In most wealthy and in many middle income countries, capsular group B Neisseria meningitidis (MenB) remains an important cause of invasive disease, particularly in the era of control of other major bacterial pathogens, such as MenC, Haemophilus influenzae type b, and vaccine-type pneumococcus. Two new MenB vaccines1,2 (now licensed in many countries) provide the potential for a comprehensive approach to controlling these invasive bacterial pathogens. However, decisions about vaccination at the population level are complex when there are low rates of disease: cost-effectiveness is a particularly important factor.3

In this issue of the MJA, Archer and colleagues4 discuss the epidemiology of meningococcal disease in Australia during 1999–2015. They describe its declining incidence, with historically low levels of infection in recent years, a pattern also seen in other developed countries.5 In addition to MenC vaccines, environmental interventions (such as reducing air pollution and imposing smoking bans in public places6), have probably contributed to declines in industrialised nations. However, they are not the only drivers of change. Data from long established surveillance systems show patterns of peaks and troughs in the rates of disease over periods of decades.7 This variation probably reflects interactions between the (disease-associated) fitness of the prevalent clones and population immunity, which is acquired via nasopharyngeal colonisation and reduces the circulation of bacterial clones over time.8 Without vaccination or reductions in risk factors for transmission and disease, the arrival of a new strain, for which population immunity is limited, is likely to lead to increased disease; a recent rise in disease in the United Kingdom caused by a highly invasive capsular group W clone of N. meningitidis illustrates this point.9,10 Australian public health officials should continue to monitor the rise of MenW described by Archer and his co-authors, as this became the leading cause of meningococcal disease in Australia in 2016;11 they should also be prepared to intervene, as this clone has a high attack rate in the UK and parts of Latin America, necessitating new control programs.12 It is noteworthy that this particular capsular group W strain might be controlled by the new MenB vaccine,13 the focus of the article in this issue.

Archer and colleagues discuss the decision to not fund MenB vaccination through the National Immunisation Program in Australia because of the current low incidence of disease. During 2005–2016 the attack rate for MenB disease in children under 12 months of age was about 10 per 100 000 population; in the UK, the rate for this age group was about 45 per 100 000 in 2006/07, falling to 20 per 100 000 in 2015/16.14 These differences in disease epidemiology over time and between countries highlight the difficulty faced by policy makers when dealing with future uncertainty when planning vaccine programs; a decision to fund vaccination would be more palatable if discussed during a period of increased disease incidence.

The rate of meningococcal disease in Australia, as in the UK, is highest among infants, making this group the obvious target for vaccination; MenB vaccination of infants was indeed added to the UK national immunisation program in September 2015. The decision was not straightforward, as uncertainty about the protection afforded and the costs was considerable. Recent post-implementation data indicate the vaccine is highly effective against invasive disease,15 matching some of the more optimistic scenarios discussed before its introduction.3 For countries still considering implementation, these data reduce some of the uncertainty about vaccine impact, and they also confirm the approach adopted in the UK for cost-effectiveness analyses, which indicated that the vaccine would be cost-effective at a low vaccine price. The duration of protection will only become apparent with time, but as the highest attack rate is during the first 2 years of life, even a moderate duration could be significant. Another problem that worries policy makers is the association of MenB vaccination with acute febrile reactions,16 mitigated to some extent by prophylactic antipyretic medication, as recommended in the UK.17

Perhaps the most important observation by Archer and colleagues regards the disparities between populations in Australia in both disease incidence and access to privately funded vaccination. Including multicomponent MenB vaccine in the national vaccination program was considered, but not recommended in view of uncertainty about its efficacy and cost-effectiveness,18 although the first question has now been resolved by the UK experience.15 Some of the highest contemporary disease rates in the developed world affect Australian Indigenous people, as documented in their article, with the incidence rate of 32.5 per 100 000 infants under 12 months of age similar to that for UK infants during the same period.14 High rates of meningococcal disease in other population subgroups have been described, including the exceptional rates among New Zealand Māori and Pacific Islanders.19 Vaccination programs that target risk groups can be difficult to implement and sustain, but such disparities in health should not be ignored, particularly when an effective intervention is available.

Authors

  • Andrew J Pollard1
  • Hannah Christensen2
  • 1. University of Oxford, Oxford, United Kingdom
  • 2. University of Bristol, Bristol, United Kingdom

Correspondence: andrew.pollard@paediatrics.ox.ac.uk

Competing interests

Andrew Pollard has conducted studies on behalf of Oxford University funded by vaccine manufacturers, but does not currently undertake industry-funded clinical trials. Trials of vaccines or observational studies previously funded by Okairos, Novartis and Pfizer were completed in the past 3 years. His department received unrestricted educational grants from Pfizer/GSK/Astra Zeneca in July 2016 for a course on Infection and Immunity in Children. Andrew Pollard chairs the United Kingdom Department of Health Joint Committee on Vaccination and Immunisation, and is a member of the World Health Organization Strategic Advisory Group of Experts. Hannah Christensen has received an honorarium from Sanofi Pasteur, and consultancy fees from IMS Health, AstraZeneca, and GSK, all paid to her employer.

Acknowledgements

Hannah Christensen is supported by the National Institute for Health Research (NIHR) Health Protection Research Unit in Evaluation of Interventions at the University of Bristol, in partnership with Public Health England. The views expressed in this article are those of the authors and do not necessarily reflect those of the National Health Service, the NIHR, the Department of Health, or Public Health England.

References

Linked content

  • MJA Research: Epidemiology of invasive meningococcal B disease in Australia, 1999–2015: priority populations for vaccination

  • MJA InSight: Meningococcal B vaccine: why aren’t we using it more?

Provenance: : Commissioned; externally peer reviewed.

View this article on Wiley Online Library

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