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Antiviral vaccines have contributed substantially to a reduction in the morbidity and mortality suffered from viral infectious diseases, especially during the second half of the 20th century. The efficacy of traditional live-attenuated and inactivated vaccine formulations, however, has been limited for some viral diseases, due to either virus-specific or host-related challenges. The application of genetic engineering technologies developed in the past decades allows for the creation of novel subunit vaccines, viral vector vaccines and nucleic acid-based vaccines. These vaccines, in some cases complemented by novel adjuvants, elicit a more finely controlled immunological response that more effectively prevents certain viral infections. They can be tailored for immunologically hyporesponsive individuals or rapidly mount protection during an outbreak. This article provides an overview of these technologies and how they have been applied in vaccines that have recently become available.

The main subject of this essay is the analysis of the immunizing properties and possible side effects of DTP (whole cell)-polio vaccine, which since 1964 is the backbone of the immunization programme in the Netherlands. The concept, that the basis of the immunity conferred by diphtheria and tetanus toxoid and inactivated poliovirus is humoral, is now generally accepted. Assessment of the potency of these three components is based on their binding properties to specific immunoglobulines in standard-antisera. An example is the testing of neutralising antibodies against the three types of poliovirus in sera obtained from different groups of infants injected with increasing doses of this vaccine. Side-effects after injecting diphtheria- and tetanus toxoids and three types inactivated poliovaccine are negligible. For the pertussis component of the vaccine, this is not the case. The standardization of the potency of cellular pertussis vaccine is still based on the analysis of the protective capacity of a number of plain vaccine lots in the intercerebral mouse-protection test relative to the protection they confer in children. An international standard vaccine is available for this purpose, and the potency of individual lots can be expressed in International Units. At present acellular pertussis vaccines are also available for immunization against this disease. The components of such vaccines are at least for a number of components, arbitrarily chosen. Recently in a trial in Sweden, a five-component pertussis vaccine has given a similar protection of infants as a cellular vaccine of British origin. In addition this acellular vaccine induced less febrile reactions. However, acellular vaccines do not protect mice against intracerebral infection. because producers have decided to omit the "Outer Membrane Complex (OMC) as a component of the vaccine. In addition it has recently been shown that the presence of the cellular pertussis component in DPT vaccine will almost completely suppress tetanus antitoxins in the IgE fraction of the serum. This observation could indicate that this suppression is the result of a cellular immunity reaction by components in the bacteria.