Haemophilus influenzae type b immunization in infants in the United Kingdom: effects of diphtheria/tetanus/acellular pertussis/Hib combination vaccine, significant prematurity, and a fourth dose.
OBJECTIVE
To measure anti-polyribosylribitolphosphate (PRP) antibody and anti-tetanus toxoid (TT) antibody responses in UK infants to explore the effects of (1) immunization with an acellular diphtheria/tetanus/pertussis/Haemophilus influenzae type b (DTPHib) combination vaccine, (2) significant preterm delivery, and (3) a fourth dose of conjugated Hib vaccine (PRP-T) in those with a low anti-PRP antibody (<1.0 microg/mL) after primary immunization.


METHODS
A prospective study was conducted in 4 tertiary neonatal units at a time when 2 types of DTPHib vaccines were used interchangeably in the United Kingdom for primary immunization: acellular (DTPaHib) and whole cell. Timing and type of all vaccine doses were as per standard UK practice. Blood was taken before and after immunization. A total of 166 preterm and 45 term infants completed the study; 97 (15 term) infants who had anti-PRP antibody <1.0 microg/mL were offered a fourth dose of PRP-T; 61 (55 preterm) then had repeat antibody measurements. Anti-PRP and anti-TT antibody after primary immunization relative to gestation and number of whole cell vaccine doses received was measured, as well as anti-PRP antibody after a fourth dose of PRP-T.


RESULTS
A total of 49% of preterm and 33% of term infants had anti-PRP antibody <1.0 microg/mL after full primary immunization. Receipt of 1 or more acellular vaccine doses was associated with lower anti-PRP antibody, a dose response effect being observed. Preterm infants were less likely to have anti-PRP antibody >1.0 microg/mL compared with term infants. A total of 93% of infants who were given a fourth dose had anti-PRP antibody >1.0 microg/mL. Anti-TT antibody responses were satisfactory for all infants but also reduced by each DTPaHib dose received.


CONCLUSIONS
Infants who receive DTPaHib, are significantly preterm, or who do not receive a fourth dose of conjugated Hib vaccine may be at increased risk for Hib disease.
Department of Neonatology, Royal Victoria Infirmary, Newcastle Upon Tyne, England.
Janet E
JE
Berrington
Andrew J
AJ
Cant
John N S
JN
Matthews
Marilyn
M
O'Keeffe
Gavin P
GP
Spickett
Alan C
AC
Fenton
D000907:Antibodies, Bacterial / Q000276:immunology*; D016667:Bacterial Capsules; D022681:Diphtheria-Tetanus-acellular Pertussis Vaccines / Q000276:immunology*; D004306:Dose-Response Relationship, Immunologic; D006192:Haemophilus Infections / Q000517:prevention & control*; D018073:Haemophilus Vaccines / Q000008:administration & dosage / Q000276:immunology*; D019741:Haemophilus influenzae type b / Q000276:immunology*; D006801:Humans; D007114:Immunization; D007117:Immunization, Secondary; D007231:Infant, Newborn; D007234:Infant, Premature / Q000276:immunology*; D011134:Polysaccharides / Q000276:immunology; D011135:Polysaccharides, Bacterial / Q000276:immunology*; D013745:Tetanus Toxoid / Q000008:administration & dosage / Q000276:immunology*; D017778:Vaccines, Combined; D018074:Vaccines, Conjugate
D000907:Antibodies, Bacterial; D022681:Diphtheria-Tetanus-acellular Pertussis Vaccines; D018073:Haemophilus Vaccines; C055753:Haemophilus influenza type b polysaccharide vaccine-tetanus toxin conjugate; C044237:Haemophilus influenzae type b polysaccharide vaccine; D011134:Polysaccharides; D011135:Polysaccharides, Bacterial; D013745:Tetanus Toxoid; D017778:Vaccines, Combined; D018074:Vaccines, Conjugate; C008984:polyribitol phosphate