Effect of Vaccine Use in the Evolution of Mexican Lineage H5N2 Avian Influenza Virus

Abstract

An outbreak of avian influenza (AI) caused by a low-pathogenic H5N2 type A influenza virus began in

Effect of Infection with a Mesogenic Strain of Newcastle Disease Virus on Infection with Highly Pathogenic Avian Influenza Virus in Chickens

“…The use of vaccine as a control measure should be utilized in a strategic manner, most effectively accomplished if maintained as the responsibility of the national veterinary services, whose decisions are based on the epidemiological situation, risk analysis, commercial and economic considerations. Continual use of avian influenza vaccine without constant assessment of its effectiveness against the circulating viruses may place pressure on the virus to undergo increased genetic drift and to accumulate mutations, which might eventually lead to development of a new HPAI strain against which the vaccine in use is not effective 24 .…”

The beneficial effects of vaccination on the evolution of seasonal influenza

“…First, by reducing the prevalence of infection, they reduce viral population size and thus the probability that antigenic escape mutants will arise. Second, although vaccination increases the growth rate of antigenically distant mutants relative to less distant mutants (which can lead to strain replacement in other pathogens [14][15][16][17][18][19][20]), it also increases the amount of immunity in the population. This increased immunity reduces the growth rate or invasion fitness of escape mutants, slowing the rate of strain replacement (SI 1.1, Eq.…”

Molecular epidemiology of avian influenza viruses circulating among healthy poultry flocks in farms in northern Vietnam

“…Since then, the epidemic waves of H5N1 among poultry had apparently subsided and the cases have been absent for approximately 14 months until the end of May 2007 when the 4 th epidemic wave was identified in the Red River Delta (Minh et al, 2009). Lee et al (2004) reported that long-term use of avian influenza vaccine among poultry in Mexico has aided the emergence of viruses with multiple sublineages separated from that of vaccine strain and subsequently allowed the newly emerged H5N2 strains spread to adjacent countries. Vietnam is a country where multiple clades of H5N1 virus have been endemic among poultry and it is, therefore, intriguing to monitor the distribution of avian influenza viruses in poultry raised in farms after introduction of the mass vaccination campaign, by which H5N1 strains were implicated to maintaine in reservoir(s) developing milder symptoms on H5N1 virus 5 infections.…”