ERS: Intra-nasal vaccine effective against influenza A in children
By Cameron Johnston
Special to DG News
STOCKHOLM, SWEDEN -- September 18, 2002 -- An
intra-nasal vaccine has proven effective at blocking the transmission of the
influenza virus among children in a daycare centre in Finland.
FluMist (Aviron) is a cold-adapted live
attenuated intra-nasal vaccine that is effective against two widespread
strains of paediatric influenza -- the Wuhan H3/2N and the A/Sydney H3/2N
strains.
In the Finnish study, presented here Sept. 16th
at the 12th
annual meeting of the European Respiratory Society (ERS), 200 children aged
12 to 36 months old, all attending daycare centres, were randomised to
receive either the flu vaccine (0.25 mL per nostril) or a placebo. An equal
number of children were assigned to each group, as it was reasoned that
children in this kind of setting mix freely and therefore if the children
were exposed one-on-one to each other (those who received the drug and those
who did not) there would be a high risk of them transmitting the vaccine
among their playmates.
Nasal swabs were taken eight times over a
21-day period.
The concept of cold-adapted vaccines is not
new, but it has taken decades to perfect the process, explained Dr. Timo
Vesikari, a professor of medicine at Tempere University, in Tempere,
Finland. This particular cold-activated vaccine, he said, is designed to
work in the temperatures of the upper respiratory tract, including the nasal
passages, but not in the warmer temperatures of the lungs.
By day 17 of the study, 80 percent of the virus
had been isolated in
the vaccination group compared with just seven
percent in the placebo group.
At the same time, there was just one reported
case of influenza B being transmitted, but no cases of influenza A being
transmitted.
There was no significant difference in the rate
of nasal discharge, Dr. Vesikari added, but this is not a good marker
because at any given time, as many as half of the children in any daycare
centre will have a discharge.
The efficacy rate seen in this small study
means the intra-nasal vaccine is "at least as effective" as the injectable
influenza vaccine, but obviously is easier to administer.
The new vaccine, he added, is a "welcome tool"
in the fight against influenza in children, and given that influenza A is
responsible for "a sizable chunk" of all otitis media cases, then "a vaccine
against influenza A might also represent a vaccine against otitis media," he
said.