Glycoprotein-specific antibody titres were significantly increased in participants in the low-dose and high-dose vaccine groups at both day 14 ( geometric mean titre 4214 [ 95 % CI 2497-7113 ] and 8205 [ 5989-11240 ] , respectively ; p < 00001 ) and day 28 ( 6827 [ 4243-10985 ] and 13057 [ 9701-17572 ] , respectively ; p < 00001 ) .