Select Committee on Science and Technology Written Evidence

Memorandum by Dr Natasha S Crowcroft, Consultant Epidemiologist, PHLS CDSC

  I write as an individual working in the Public Health Laboratory Service (PHLS) Communicable Disease Surveillance Centre (CDSC) Immunisation Division. My submission focuses on vaccine preventable disease, particularly on aspects relating to prevention and surveillance.

1.   What are the main problems facing the surveillance, treatment and prevention of human infectious disease in the UK?

  The UK is internationally respected for the high quality of its vaccination programmes including surveillance of vaccine preventable disease. For vaccination programmes, surveillance includes not only monitoring disease incidence, but also vaccination coverage, population susceptibility through serosurveys, and vaccine adverse events. Vaccination is recognised by the World Health Organization (WHO) to be the most effective health intervention after provision of clean water, but the lives saved by a well implemented programme are often taken for granted.

  When vaccination coverage is high and the infections rare, it becomes hard to maintain the priority of surveillance. The enormous benefits of vaccination are taken for granted and this presents one of the main problems in obtaining sufficient core resources for surveillance. Some of the key policy work being carried out at national level for the UK is supported through grant funding rather than with core support.

  When vaccine preventable infections become rare it is important for surveillance to be even more intensive (and expensive) than that required when they are more common. This is important to monitor the efficacy of the vaccines in use and to meet WHO requirements. Surveillance becomes more difficult because:

    —  Clinical notifications are incomplete (grossly so for infections such as pertussis where probably less than one in 10 infections are notified).

    —  The positive predictive value of clinical case definitions falls with falling disease incidence. For example, most infections notified as measles now prove not to be measles, where 20 years ago the majority would have been confirmed.

    —  Important information in routine laboratory data and notifications is often missing, such as vaccination status and batch numbers of vaccines. For example, nearly 90 per cent of hepatitis A virus infection laboratory reports have no information about whether the infection may have been acquired abroad.

  In response to these challenges we have moved from using clinical notifications to requiring laboratory confirmation and from passive surveillance to enhanced surveillance for diphtheria, tetanus, pertussis, polio, measles, mumps, rubella, Haemophilus influenzae b, and meningococcal infection. Enhanced surveillance improves the specificity of reporting but does not necessarily improve its sensitivity (completeness).

  For some diseases detailed microbiological surveillance is required for public health purposes. For examples:

    —  Pertactin typing of Bordetella pertussis has been carried out to examine whether in the UK any immune selection by vaccination can be observed that might lead to a resurgence of pertussis as seen in the 1990s in the Netherlands.

    —  Subtyping of Neisseria meningitidis to see whether implementation of the Group C meningococcal vaccination programme may lead to capsular switching or a resurgence of a different serogroup. Much of this typing is carried out solely for public health purposes and has no implications for individual diagnostics.

  Vaccination coverage data is a critical tool for monitoring the delivery of the programme and has been obtained on behalf of the Department of health by CDSC from the Child Health Computer System of Community Trusts. Although the data are not perfect, they have been amongst the best in the world as few countries have a population-based system of measuring coverage. Following the dissolution of health authorities, Primary Care Trusts have the prime responsibility for the health of local populations. Some District Immunisation Co-ordinators now work in different organisations separating them from the locus of responsibility and sometimes from access to coverage data. For example, some of those who are paediatricians have moved to the local acute hospital trust. The problems from the managerial re-organisation are exacerbated by new administrative boundaries. Furthermore, PCTs' responsibilities are more easily interpreted in terms of GP practices than geographically defined populations and unregistered patients risk being neglected. Some GPs are frustrated because they are asked to provide different data for their vaccination target payments from that required for the Child Health System. Some PCTs are examining ways to collect coverage data directly from GPs which will not easily be referred to a geographical population. Maintenance of coverage data is currently being challenged by such health service re-organisation.

  Serosurveys of susceptibility have been carried out by the PHLS using its network of laboratories. It is not clear where lies the future of this surveillance if, as appears to be the current model, the new Health Protection Agency passes the whole laboratory network over to the NHS.

  Vaccine adverse events surveillance, the responsibility of the Medicine Control Agency, relies primarily on passive reporting through the "Yellow card" scheme. This is known to be incomplete. In the current climate where parents fear the vaccines much more than the diseases they prevent, a current challenge is to improve the system of adverse events surveillance to be able to provide more accurate information and faster detection of problems especially as new vaccines are added to the programme.

  The rarity of vaccine preventable diseases following the success of the programme also makes the task of convincing parents and recipients of vaccines of their necessity. Parents and health care workers now have little experience of how severe vaccine preventable infections can be and often do not realise how quickly they can resurge if vaccination coverage falls, as seen during the large epidemics of whooping cough which followed the pertussis vaccine scare in the 1970s. The issue here is of risk communication and how to improve the media's and the public's understanding, not just of science but also of the robust and independent public health infrastructure which underpins the whole vaccination programme.

  For health care workers delivering the vaccination programme in primary care training has been extremely limited. Practice nurses and health visitors receive little training beyond the basic practical skills and this puts them in a difficult position when trying to act as advocates for immunisation with parents. A joint venture between PHLS and City University has recently started providing university level training on the rationale and scientific basis of vaccination aimed at primary care professionals, to our knowledge the only training at this level currently available in England.

  The requirements to protect data may threaten the quality of surveillance. This is a particular challenge for adverse events surveillance where data linkage studies (which require patient identifiable information) have proved enormously powerful in enabling us to examine hypotheses that a particular vaccine is associated with an adverse events extremely rapidly. For example, a link was proposed in recent years between oral polio virus vaccine and intussusception. This hypothesis was examined in a data linkage study and disproved rapidly. In order to have a sensitive threshold to detect real adverse effects of vaccines, public health authorities should examine every possible serious vaccine reaction and provide reassurance, estimate risk or advise withdrawal of the vaccine in question, as soon as possible. Such sensitivity to examine every allegation means that most of the analyses carried out are likely to prove negative and should be as fast as possible to avoid unnecessary damage to the programme.

2.   Will these problems be adequately addressed by the government's recent infectious disease strategy, Getting Ahead of the Curve

  It is not clear yet whether "Getting Ahead of the Curve" (GAC) will address the problems outlined. The main area of concern is public health microbiology. As outlined above, vaccine preventable disease surveillance relies enormously on close multidisciplinary collaboration between microbiology and public health. The existing network of Public Health Laboratories has enabled:

    —  Enhanced national surveillance of vaccine preventable disease.

    —  Rapid development and implementation of evidence-based guidance for investigating and controlling infectious diseases, such as the Guidance on Rash and Exposure to Rash in pregnancy produced by the PHLS.

    —  Rapid development of advanced reference diagnostic methods such as polymerase chain reaction for pertussis, and genotyping of hepatitis A virus infection.

    —  Development and implementation of standard operating procedures for diagnostic and public health microbiology, such as the throat swab screening for Corynebacterium diphtheriae and C.ulcerans standard operating procedure which is implemented in almost all Public Health Laboratories but only around half of NHS laboratories.

    —  Serosurveillance.

  It is not clear in GAC how such developments could come about or be as effective because the laboratory network will no longer exist and local autonomy will increase, so local priorities may hamper response to national priorities.

  The proposal in GAC to modernise the collection of vaccination coverage data is welcome although the recommended development is still awaited.

  Aspects of surveillance relating to the vaccination programme not really addressed by GAC are adverse event surveillance and training of primary care staff.

    —  Adverse events surveillance should be as good as disease surveillance.

    —  Minimum standards are needed for the training of health care workers delivering the vaccination programme and should be required by PCTs for practice nurses, health visitors and GPs. Practice nurses in particular experience difficulties obtaining time and financial support for training and so would benefit from managerial support for this from the PCTs.

3.   Is the UK benefiting from advances in surveillance and diagnostic technologies; if not, what are the obstacles to doing so?

  The PHLS has provided an efficient channel for rolling out advances in surveillance and diagnostic technology. Although the implications of GAC are not fully defined, current indications are that the dismantling of the network is likely to undermine future capacity. Re-organisation of health care at local level is a further obstacle weakening established relationships between local public health and microbiology which support detection of vaccine preventable infections and monitoring of vaccination coverage.

  Public health legislation requires that statutory notifications be made in writing and as a result completeness of reporting is low for most infections. Changes in the law and agreement on transfer of patient identifiable information for public health purposes with improved use of internet technology might enable improved completeness of reporting.

  Data linkage is an important tool for disease surveillance, estimation of priorities for existing and new vaccines and adverse events investigation. Greater use could be made of several large data sets including the General Practice Research Database (GPRD) and Hospital Episode Statistics (HES), especially if access to the data and timeliness of its availability were improved and greater data linkage employed through implementation of the new NHS number. Requirements of patient confidentiality also threaten the ability to carry out data linkage studies.

  Near patient testing has exciting potential to improve specificity of diagnosis in primary care of infections such as respiratory syncytial virus (RSV) and influenza. Careful consideration needs to be given to how such new technology can be incorporated into laboratory surveillance.

  In providing greater flexibility of NHS services walk-in clinics are developing which may lead to some cases being lost to surveillance which may have been detected previously.

4.   Should the UK make greater use of vaccines to combat infection and what problems exist for developing new, more effective or safer vaccines

  Vaccines offer the best opportunity to control infectious diseases with high incidence such as pneumococcal infection as well as to combat rising antibiotic resistance. New vaccines on the horizon include licensed vaccines such as new conjugate pneumococcal vaccines and varicella zoster virus vaccine and vaccines under development including new influenza vaccines (live attenuated), Group B meningococcal vaccines, RSV vaccines. However, with the challenges to the existing programme in the UK including parents (unfounded) fears that vaccines may overload an infants' immune system it may prove difficult to add additional vaccines to the programme. Better public understanding of science and of public health is required. Implementation of vaccination programmes for adults are even more challenging than for children. For example, in the USA the adult 10 yearly tetanus booster programme has uptake of only around 50 per cent although vaccination is generally supported.

  The first problem faced in developing new more effective or safer vaccines is the enormous resource necessary to meet safety requirements. For some infectious diseases, vaccines have not yet been developed because the characteristics of the organism make it harder to control than the organisms for which existing vaccines were developed. For example, unlike measles, RSV causes multiple infections throughout life. It is harder to develop a vaccine which stimulates long term immunity as this requires an improvement on nature, with no effective natural immune response to mimic. In addition, a previous RSV trial vaccine (formalin inactivated) caused a worsening of RSV infection and so the pharmaceutical industry is rightly cautious as a result.

  Sometimes there is a trade off between safety and effectiveness. For example, many countries have moved to using acellular pertussis vaccines from whole cell vaccines because adverse reactions are less frequent. However, nearly all acellular vaccines are less effective than a good whole cell vaccine.

  New challenges come from advances in medicine which mean that more vulnerable individuals are surviving and require protection. For example, there are more surviving infants born prematurely, immunocompromised individuals (through treatment or disease) and extremely elderly individuals. Some such individuals cannot make an immune response to existing vaccines, and for some live vaccines may be dangerous, so new approaches are required.

5.   Which infectious diseases post the biggest threats in the foreseeable future?

  If vaccine scares continue to threaten the national programmes and the recent falls in coverage of all vaccines continues (including diphtheria, tetanus and pertussis as well as measles mumps and rubella) then these diseases will come back. A resurgence of rubella in children would be expected to be associated with an increase in congenital rubella syndrome as well. Of the diseases in the current programme, pertussis is probably the worst controlled infection and additional boosters may be needed eventually for adolescents and possibly adults. Pandemic influenza remains a great threat. The potential for bioterrorist attacks using smallpox or anthrax has added a new dimension to the threat of vaccine preventable disease.

6.   What policy interventions would have the greatest impact on preventing outbreaks of and damage caused by infectious disease in the UK?

  A public health network of laboratories is required to support a strong network of public health reference laboratories and epidemiologists. Public health microbiology is qualitatively different from diagnostic microbiology. The work of public health professionals such as consultants in communicable disease control, regional and national epidemiologists should be fully integrated with microbiology as the two approaches are complementary and interdependent. GAC seems to risk enhancing rather than bridging the divide between public health epidemiology and microbiology.

  National standards need to be maintained and developed for investigation, treatment, surveillance and control of vaccine preventable diseases. This includes safeguarding and improving collection of vaccination coverage data and serosurveillance. Lines of accountability and national priorities need to be clearly defined so that local priorities do not detract from surveillance of the national programme. The national vaccination programme also has to take account of the international context including requirements of the WHO.

  Improving public and media understanding of science, risk and public health is a major multi-agency policy area. For example, schools could promote vaccination to protect all children in the school and as part of the school's duty of care. It may become important for parents to know the vaccination coverage of children in the school or nursery which their child or children attends so they can assess the risk of outbreaks. Vaccination should be seen as a child protection issue—like putting on a child's safety belt in the car. Vaccination as a subject could be incorporated into the national curriculum.

  The quality and completeness of information on vaccinations falls with increasing age—even by the time of the pre-school booster the vaccination coverage data quality is starting to decline, and information on uptake of the school-leaving booster programme is sketchy. As new vaccines are introduced for adults, a system for delivering and monitoring adult vaccination also needs to be developed which is equivalent to the childhood system.

  The quality of vaccine adverse events surveillance should be at least the same as disease surveillance. Members of the public could report straight to the medicines control agency. For example, parents could be given a report form at each vaccination with a reporting telephone number. To respond rapidly to scares, an extensive core funded infrastructure should be available including epidemiologists and mathematical modellers with access to the datasets required.

previous page contents next page

House of Lords home page Parliament home page House of Commons home page search page enquiries index

© Parliamentary copyright 2003