Immunogenicity and safety of an inactivate pandemic H1N1 vaccine provided by the Thai ministry of public health as a routine public health service.
A prospective study was conducted among 252 participants to study the immunogenicity of unadjuvanted inactivated H1N1 influenza vaccine, using a hemagglutination inhibition (HAI) assay, conducted on Days 0 and 21 following immunization. Adverse events (AEs) were monitored for by interview. The mean age of participants (+/- SD) was 45 (+/- 11) years. Seventy percent of participants had no history of major medical problems, 28% had a chronic illness and 2% were pregnant women. The HAI assay geometric mean titer (GMT) was 6.9 on Day 0 and 33.4 on Day 21 (4.8 times, p<0.001). The proportion of participants who had a HAI assay titers > or = 40 was 7% (19/252) on Day 0. Those who had a titer > or = 40 and/or a 4-fold rise in their HAI titer on Day 21 was 62% (155/252) (p<0.001). Fifty-six percent (142/252) had a four-fold increase in their HAI assay titer. Of the 19 subjects with a Day 0 HAI assay titer >40, 10 (53%) had a four-fold increases in their HAI assay titer after vaccination. On multivariate analysis, only "older age" was associated with a lower probability of immune response (OR 0.5; 95%CI 0.3-0.8). No serious systemic AEs were reported. Mild erythema and local reaction on Day 2 were reported in 9% (23 of 252). The antibody response after a single dose of inactivated monovalent H1N1 vaccination in this study was relatively low, especially in the older age group. A booster H1N1 vaccine dose may be needed. The vaccine was safe and well tolerated.
Department of Disease Control, Ministry of Public Health, Nonthaburi, Thailand.
Opart
O
Kankawinpong
Chariya
C
Sangsajja
Arjin
A
Cholapand
Weerawat
W
Manosuthi
Varaporn
V
Thientong
Naviya
N
Nuntapanich
Pantip
P
Rompotal
Pilaipan
P
Puthavathana
D000328:Adult; D000914:Antibodies, Viral / Q000276:immunology; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000009:adverse effects / Q000276:immunology*; D007251:Influenza, Human / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D015980:Public Health Practice; D013785:Thailand / Q000453:epidemiology; D015164:Vaccines, Inactivated
D000914:Antibodies, Viral; D007252:Influenza Vaccines; D015164:Vaccines, Inactivated