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Many people are no longer familiar with the diseases that are part of the Dutch National Immunisation Programme (NIP). The protection given by the NIP has ensured that these diseases, most of them serious, have largely disappeared. The NIP has developed gradually, but in retrospect it was in 1957 that what we now know as the NIP started. Over the years, the NIP has gradually expanded to include various vaccines such as live attenuated vaccines, conjugate vaccines and vaccines that offer protection against chronic viral infections. Currently, the NIP offers protection against twelve different diseases. Occasionally the Netherlands still sees minor outbreaks of those diseases included in the NIP programme, generally among non-vaccinated people. It is important that the NIP is retained; stopping vaccination always leads to the return of the disease. The question is: can good protection be maintained with fewer injections? This subject is on the agenda of the Health Council Of The Netherlands for discussion in 2022.

The national vaccination rate in young children in the Netherlands has decreased in recent years. This has led to social and political discussions, for instance about compulsory vaccination for children in child-care. The national commission on child-care and vaccination has advised that vaccination should be made compulsory when the rate of vaccination has declined to a pre-determined lower threshold, to be determined by the government. A frequently quoted lower threshold is 95%. The idea behind this is the concept of a critical vaccination rate, a threshold needed for elimination of an infection in a large, well-mixed population. In this article we argue why the critical vaccination rate does not offer a scientific basis for a lower threshold to the national vaccination rate.

Expectations are that 25% of the Dutch population will be aged 65 years or older in 2050 whilst in 2008 this proportion was only 15%. As a consequence the annual absolute number of new cases of specific infectious diseases will increase. Elderly people often have less clear symptoms of infection, making it harder for clinicians to recognize the disease. Morbidity and mortality caused by infections increase with age. Ageing will possibly cause an increase in levels of antibiotic resistance. There will be more elderly people in hospitals and nursing homes, where more antibiotics are used. This development will come in addition to other developments in the field of antibiotic resistance. There will be more elderly people with chronic HIV and viral hepatitis B and C infection and their complications because patients who are presently infected with those pathogens are ageing. Policy makers should more often consider introducing vaccination of older age groups against certain infectious diseases.

The Dutch Public Health Act, which came into force on 1 December 2008, replaces the existing laws concerning the combating of infectious diseases. Important changes have been incorporated in the new Public Health Act in comparison with the previous law on infectious diseases. Diseases which are probably infectious in nature and caused by as yet unknown pathogens are now notifiable, laboratories also have a nominal duty of notification and the list of notifiable diseases has been extended with 10 new infectious diseases. The provisions in the law comply with the International Health Regulations of the World Health Organization. The Centre for Infectious Disease Control Netherlands at the Dutch National Institute for Public Health and the Environment (RIVM) has issued a booklet for all Dutch physicians and laboratories providing background information on notifiable diseases. This can be useful in daily practice for helping to decide whether a disorder or cluster of infections is notifiable.

Climate change is associated with changes in the occurrence of arthropod-borne diseases. It is difficult to foresee which arthropod-borne diseases will appear in the Netherlands due to climate change. Climate change influences the prevalence of ticks and may lead to a further increase in Lyme disease and an increased risk of the introduction of rickettsioses. With further warming of the climate there is a real possibility of settlement of the mosquito Aedes albopictus and introduction of the sandfly in the Netherlands. Whether this will lead to circulation of micro-organisms transmitted by these vectors (e.g. West Nile virus, Dengue virus, Leishmania) is not clear. Continued vigilance is necessary, even for vector-borne diseases that appear to be less relevant for the Netherlands.

Based on the changes in the epidemiology of infectious diseases in the Netherlands in 2000-2005, it is possible to formulate a prediction for the immediate future. Developments that one may expect with a reasonable amount of certainty are a further rise in sexually transmitted diseases, continued vulnerability for infectious diseases for which the State Vaccination Programme distributes vaccines, a slow increase in bacterial resistance, an increase in opportunistic infections, and growing risks for the introduction of new micro-organisms via international travel and trade. Much less certain are the developments surrounding avian influenza A/H5N1, ticks and mosquitoes, the rise and spread of new diseases, and bioterrorism.

Since 2004, outbreaks of fowl plague caused by a highly pathogenic avian influenza virus of the subtype A/H5NI have been reported from various countries in Southeast Asia. To date, 118 cases with 61 deaths have been documented in humans, due to close contact with infected poultry or raw poultry meat. Although efficient human-to-human transmission has not occurred, in a few cases transmission to blood relatives could not be ruled out. In October 2005, outbreaks of A/H5NI in poultry and wild fowl have been confirmed from Turkey, Romania and Russia, due probably to infection via migratory birds. The direct risk of infection in humans in Europe is very low and is associated with direct exposure to infected poultry. In order to address the long-term risk of a pandemic due to recombination of human and avian viruses or to mutations in the avian virus itself, guidelines for pandemic preparedness have been developed and implemented in the Netherlands.

Objective: To establish whether the meetings of the so-called 'early warning committee' recognise all the threats to the public health in the Netherlands caused by infectious diseases., Design: Retrospective and descriptive evaluation., Method: The information about the outbreaks of infectious diseases in the Netherlands and about events in the area of infectious diseases in foreign countries was compared with the domestic and foreign reports discussed in the regular weekly meetings of the Dutch early warning committee. For this purpose, the authors summarized the outbreaks of infectious diseases in the Netherlands in 2002 and 2003 as reported in articles in the Nederlands Tijdschrift voor Geneeskunde (Dutch Journal of Medicine). This summary was then compared with the domestic reports discussed in the meetings of the early warning committee. If an outbreak was not mentioned in the meetings of the early warning committee, the cause for this was established. For the same period, a summary was made of the foreign events in the area of infectious diseases and this was also compared with the foreign reports mentioned in the meetings of the early warning committee. When an event had not been discussed in the meetings of the early warning committee, it was established on the basis of criteria whether the event could have been a threat to public health in the Netherlands., Results: All outbreaks of infectious diseases in the Netherlands had been discussed in the early warning committee. Of the foreign events in 2002, 3 had not been discussed in the committee although they should have been, based on the criteria for a potential threat to the Netherlands: the outbreak of avian influenza A/H5NI in domestic fowl in Hong Kong, the increase among hospitalised patients of carriers of extended-spectrum 3-lactamase producing micro-organisms in Scotland, and outbreaks of measles in several countries. In 2003, all foreign events that could have been a threat to the Netherlands were discussed in the early warning committee., Conclusion: In 2002 and 2003, the meetings of the early warning committee recognised practically all the outbreaks of and threats due to infectious diseases.

Syndromic surveillance has been developed in order to detect outbreaks of unusual infectious diseases such as severe acute respiratory syndrome (SARS) or anthrax at an early stage. Whereas the usual surveillance systems are based on established diagnoses and emergency department discharge data, syndromic surveillance uses preliminary outcomes and derived data such as absenteeism, prescription medication and requests for laboratory tests. Investigations abroad have indicated the potential ofsyndromic surveillance. In the Netherlands, the National Institute of Public Health and Environment (RIVM) is examining the feasibility of implementing syndromic surveillance.

Objective: To determine the risk factors that contribute to the transmission and return of scabies in health care institutions., Design: Literature analysis., Setting: Public Health Care Service Midden-Kennemerland. Heemskerk, the Netherlands., Methods: Search of Medline over the years 1976-1996 yielded 34 reports of 44 outbreaks. The contents were qualitatively examined on factors possibly contributing to the transmission and return of scabies in health care institutions., Results: Six such factors that contribute to the transmission and return of scabies in health care institutions were found: (a) among residents in health care institutions a considerable number are, once infested, at risk of developing crusted scabies, (b) many people are exposed through close contact, (c) the generally long diagnostic delay, (d) insufficient survey of the epidemiological problem, (e) treatment failures and (f) incomplete post-intervention monitoring.