Abstract
Vaccines are preparations of weakened or killed viruses or viral subunits that trigger specific protective immunity. Vaccination is the single most effective tool for preventing communicable disease, highlighted by the achievements of the smallpox and poliomyelitis eradication programs and the rise in infections for which no effective vaccine is available: human immunodeficiency virus, malaria, worms, and tuberculosis. World Health Organization initiatives target acute respiratory diseases in infancy and early childhood with novel immunization approaches. Effective vaccines are needed urgently for viral respiratory diseases, but progress has been disappointingly slow. Vaccine candidates often show reduced efficacy in infancy, in partially immune adults, the immunocompromised, and the elderly. However, several promising vaccines are in clinical trial, and it is likely that vaccines against respiratory syncytial virus and parainfluenza will be licensed within the next 5–10 years. Mucosally delivered influenza vaccine is now available, and novel adjuvants offer the prospect of better immunogenicity. Ideally, multivalent mucosal vaccines will be developed that provide protection against a spectrum of respiratory infections in specific target age groups.