Novel avian influenza virus vaccines.

Current vaccines against avian influenza (AI) virus infections are primarily based on classical inactivated whole-virus preparations. Although administration of these vaccines can protect poultry from clinical disease, sterile immunity is not achieved under field conditions, allowing for undetected virus spread and evolution under immune cover. Therefore, there is an urgent need for a robust and reliable system of differentiation between infected and vaccinated animals. Moreover, current AI vaccines must be administered individually, requiring the handling of excessively large numbers of animals, which makes it difficult to obtain high vaccine coverage. Consequently, AI vaccines conferring solid immunity that could be used for mass application would be advantageous. Several approaches are being pursued to improve existing vaccines and develop novel vaccines, all of which will be covered in this overview.

[Safety and immunogenicity of split vaccines of influenza viruses].

OBJECTIVE: To evaluate the safety and immunogenicity of influenza split vaccine. METHODS: According to the criteria of No.2002SL0043, instruction of application for new drug in clinical trial issued by the State Food and Drug Administration, 876 healthy persons were divided at random into vaccine group and control group. The trial was performed with the double blind method. Local and systemic adverse reactions were observed within 3 days after the vaccine group subjects were vaccinated. The antibody response to vaccines was detected with hemagglutination inhibition (HI) test. Numbers of seroconversions and HI titers greater than or equal to 40, as well as the mean geometric titer increase in HI were analyzed. RESULTS: There was no significant difference in local and systemic adverse reaction between vaccine and control groups. Meanwhile there was also no significant difference in seroconversions and protective level between two groups. However, there was obvious difference in mean geometric titer increase of antibody against H1N1 virus, while there was no significant difference in that of antibodies to H3N2 and type B viruses. CONCLUSIONS: The safety and immunogenicity of both vaccines are excellent.

[Inactivated vaccines: characteristics and principles of use]. / Les vaccins inactivés: caractéristiques et principes d'utilisation.

Inactivated vaccines are non infectious, which makes them remarkably innocuous, but implies to repeat their injections, with variable periodicity according to each vaccine, in order to maintain protective immunity. Inactivated vaccines include either complete microbial agents or purified antigenic fractions. The potency of inactivated vaccines is usually reinforced by adjuvants. Although inactivated vaccines induce a strong individual protective immunity, their use requires a high vaccine coverage among the target population in order to obtain a good herd immunity necessary to reach ambitious public health objectives such as elimination or eradication of infectious diseases.

Field trial of oral cholera vaccines in Bangladesh: results from three-year follow-up.

The protective efficacy (PE) of B subunit killed whole-cell (BS-WC) and killed whole-cell-only (WC) oral cholera vaccines was assessed in a randomised double-blind field trial among children aged 2-15 years and women over 15 years in rural Bangladesh. Among the 62 285 subjects who received three doses of BS-WC, WC, or Escherichia coli K12 strain placebo, cumulative PE at 3 years of follow-up was 50% for BS-WC and 52% for WC. PE was similar against severe and non-severe cholera, but was significantly lower in children who were vaccinated at 2-5 years (26% for BS-WC; 23% for WC) than in older persons (63% for BS-WC; 68% for WC). Among persons vaccinated at 2-5 years, protection at 4-6 months of follow-up was similar to that for older persons, but rapidly waned thereafter and was not evident during the third year of follow-up. In contrast, persons vaccinated at older ages were protected even in the third year of follow-up (PE 40% for BS-WC; 62% for WC). PE was substantially higher against classical cholera (58% for BS-WC; 60% for WC) than against El Tor cholera (39% and 40%).