Ottawa: People vaccinated against seasonal
flu appeared to have been at increased risk of the H1N1
pandemic flu that killed thousands worldwide in 2009,
Canadian researchers have said.
However, they said in their findings published in the
journal PLoS Medicine that the link between seasonal flu
vaccinations and subsequent pandemic flu illness is tenuous.
Four studies led by Danuta Skowronski of the British
Columbia Centre for Disease Control in Vancouver compared the
frequency of prior vaccination in people with H1N1 influenza
to people without evidence of infection.
The studies included approximately 2,700 people with and
without H1N1.
The first study "confirmed that the seasonal vaccine
provided protection against seasonal influenza, but found it
to be associated with an increased risk of approximately 68
per cent for H1N1 disease."
A further three studies also found an "increased
likelihood of H1N1 illness in people who had received the
seasonal vaccine compared to those who had not."
The researchers said these do not reveal a "true
cause-and-effect relationship" between seasonal flu
vaccination and subsequent H1N1 illness.
PTI