Forty-three high-risk preterm children received either one of three do
ses of purified hemagglutinin antigen (HA) (7.5 mu g/0.25ml, 22.5 mu g
/0.25ml or 67.5 mu g/0.25ml) or standard split product vaccine (ST) (2
2.5 mu g/ml dose) over the 1990-1991 influenza season. Components for
all vaccines included A/Shanghai 16/89, A/Taiwan 1/86 and B/Yamagata 1
6.88. Sera for antibody was drawn before, 6 weeks and 4 months after t
he first vaccine dose. The study was randomized and blinded. All child
ren received two 0.25 ml doses of vaccine 4 weeks apart. No significan
t local or systemic reactions occurred. Six weeks after the first dose
, children receiving ST vaccine had significantly higher seroconversio
n rates to A/Shanghai (p=0.03) and to A/Taiwan (p=0.01) than did those
receiving equivalent HA vaccine. However, seroconversion rates were s
ignificantly higher for those children receiving the highest HA dose.
All four vaccine groups responded poorly to B/Yamagata. Geometric mean
titres were low for all groups and declined over 4 months. These resu
lts suggest that the equivalent dose of HA vaccine offers no advantage
over ST vaccine in the immunization of high-risk preterm children.