Vast changes are taking place in vaccinology consequent to the introduction of new technologies. Amongst the
vaccines included in the Expanded Programme of Immunization (EPI), the
pertussis vaccine has been replaced by acellular purified fractions devoid of side-effects. Non-pathogenic but immunogenic mutants of
tetanus and diptheria toxins are likely to replace the
toxoids. An effective
vaccine against
hepatitis B prepared by recombinant technology is in large-scale use. Conjugated
vaccines against Haemophilus influenzae b, S. pneumococcus and meningococcus are now available, as also
vaccines against
mumps,
rubella and
measles.
Combination vaccines have been devised to limit the number of
injections.
Vaccine delivery systems have been developed to deliver multiple doses of the
vaccine at a single contact point. A genetically-engineered oral
vaccine for
typhoid imparts better and longer duration of immunity. Oral
vaccines for
cholera and other enteric
infections are under clinical trials. The nose as a route for immunization is showing promise for mucosal immunity and for anti-inflammatory experimental
vaccines against
multiple sclerosis and
insulin-dependent diabetes mellitus. The range of
vaccines has expanded to include pathogens resident in the body such as Helicobacter pylori (
duodenal ulcer), S. mutans (
dental caries), and human papilloma virus (
carcinoma of the cervix). An important progress is the recognition that
DNA alone can constitute the
vaccines, inducing both humoral and cell-mediated immune responses. A large number of
DNA vaccines have been made and shown interesting results in experimental animals. Live
recombinant vaccines against
rabies and
rinderpest have proven to be highly effective for controlling these
infections in the field, and those for
AIDS are under clinical trial. Potent adjuvants have added to the efficacy of the
vaccines. New technologies have emerged to 'humanize' mouse monoclonals by genetic engineering and express these efficiently in plants. These recombinant
antibodies are opening out an era of highly specific and safe therapeutic interventions. Human recombinant
antibodies would be invaluable for treating patients with terminal
tetanus and
rabies.
Antibodies are already in use for treatment of
cancer,
rheumatoid arthritis and
allergies. An advantage of preformed
antibodies directed at a defined target and given in adequate amounts is the certainty of efficacy in every recipient, in contrast to
vaccines, where the quality and quantum of immune response varies from individual to individual.