wk 2 additional - antigenic variation, zoonotic, influenza vaccines

Antigenic drift

random point mutations change H/N while retaining the same subtype, can allow evasion from immune system & decrease antibody binding

Antigenic drift mechanism

low-fedelity of RNA replication → mutations alter aaa sequences

seasonal outbreaks, epidemics

Antigenic shift

H, N & other gene segments
2 influenza viruses infect same cell → exchange gene segments thru reassortment
causes pandemics

Avian influenza transmission

primarily fecal-oral transmission

H5N1

influenza a subtype associated w/ antigenic shift, causes severe disease in humans & highly virulent in domestic birds

H7N9

Avian influenza found in humans beginning 2013, no evidence of sustained human-to-human transmission in the notes

H9N2

Aian influenza subtype found in humans, no human-human transmission

H5N6

avian influenza subtype, no human-human transmission

Zoonotic influenza pandemic risk

these viruses could potentially cause pandemics BUT not adapted yet

Inactivated influenza vaccine

most common flu vaccine/annual flu shot

Quadrivalent flu vaccine

Contains 4 influenza viuses bc multiple viruses co-circulate

Flu vaccine production

viruses are grown in eggs & inactivated

WHO vaccine selection

WHO meets in FEBRUARY for Northern Hemisphere & SEPTEMBER for Southern Hemisphere to recommend vaccine viruses
takes 3-6 months for vaccines to be produced

Flu vaccine selection factors

most common virus, most deadly strain, & grows best in eggs

FluMist

quadrivalent live attenuated influenza vaccine given intranasally
approved for ages 2-49
26% efficacy vs 51% efficacy in shot

Flu vaccine efficacy

varies bc of different strains each year