Immunogenicity of recombinant yeast-derived hepatitis B vaccine in nonresponders to perinatal immunization

OBJECTIVE

Nonresponse to hepatitis B vaccine in the perinatal period occasionally occurs. This report documents the results of reimmunization of nonresponders to perinatal immunization.

DESIGN

From a cohort of 1154 infants immunized with plasma-based vaccine in the perinatal period and followed up for more than 8 years, 45 nonresponders were identified. These children were reimmunized at 4 years of age. Each child received a yeast-derived recombinant hepatitis B vaccine on a 0-, 1-, and 5-month schedule, 33 children with 10-micrograms and 12 with 5-micrograms doses. Blood was sampled 1 month after the third vaccination and thereafter at 1, 2, and 4 years.

SETTING

The follow-up clinic where the cohort of children was regularly seen.

PATIENTS

Forty-five 4-year-old children who had no antibody to hepatitis B despite perinatal immunization.

MAIN OUTCOME MEASURE

Antibody levels to hepatitis B surface antigen.

RESULTS

Seroconversion with titers higher than 10 mIU/mL occurred in all children. More than 70% still had titers higher than 10 mIU/mL 4 years after vaccination.

CONCLUSION

Nonresponders to perinatal hepatitis B vaccination respond well to subsequent vaccination.

Efficacy of phototherapy in neonatal hyperbilirubinaemia associated with glucose-6-phosphate dehydrogenase deficient status

The efficacy of phototherapy in a group of 427 infants with hyperbilirubinaemia associated with glucose-6-phosphate dehydrogenase (G6PD) deficiency and a comparable group of 3924 G6PD normal infants with non-haemolytic hyperbilirubinaemia was evaluated. Phototherapy was highly effective in reducing bilirubin levels in both groups of infants, being significantly more effective in the group with normal G6PD status. Failure rate was very low (2.03/1000) in the group with normal G6PD status and nil in the G6PD deficient group. Bilirubin rebound after phototherapy was unremarkable with very few infants requiring a second exposure--4.68/1000 in the G6PD deficient group and 6.37/1000 in the G6PD normal group. All the babies tolerated phototherapy well. Phototherapy would therefore seem to be a simple and effective method for the management of severe jaundice associated with G6PD deficiency.

Free thyroxine as a supplement to thyrotropin in cord screening for hypothyroidism

The low specificity of cord serum T4 levels for detecting hypothyroidism, the need to reduce recall rates and the availability of a reliable and quick assay system led to this study designed to determine the advantages of using cord serum free thyroxine levels over total thyroxine levels as a supplement to cord thyroid stimulating hormone (TSH) determination. Sixty-eight out of 75 newborns with a cord TSH > 23 mU/l had both free thyroxine (fT4) and T4 levels measured in the cord serum. All were recalled within the first month of life for reevaluation of their thyroid status. In the majority of cases (46), the fT4 and T4 values corresponded. Hypothyroidism was diagnosed in eight cases; both fT4 and T4 were below the mean in five cases and above the mean in one case; only T4 was below the mean in one and in the remaining one, only fT4 was below the mean. Recall rates were 0.9% with TSH alone and 0.7% when either a fT4 or T4 level that was less than 1 sd above the mean was used as a supplement to TSH. In this cohort, using the fT4 levels instead of the T4 levels brought no change to the specificity or the sensitivity of the screening. The diagnostic sensitivity would have dropped from 100% to 75% if either T4 or fT4 values below the mean were used as a cut-off point for recall.

Poliovirus neutralising antibody in infants and cord blood

Singapore participated in the WHO EPI protocol for rapid assessment of serological response to three doses of standard oral poliovirus vaccine. The 100% seropositive finding of thirty infants below one year old is no proof of seroconversion rate to the Trivalent Oral Poliovirus Vaccine (TOPV) administered. Investigation of 100 cord blood samples showed that passively transferred maternal poliovirus neutralising antibody cannot be relied upon for protection of infants against poliomyelitis. This paper emphasises the importance of vaccine potency testing and serves as a timely reminder that although the last case of indigenous poliomyelitis was recorded in 1974, non Sabin-like (wild) polioviruses are being isolated from imported cases and foreigners hospitalised in Singapore, and unexpectedly, from the conjunctiva and pharynx of Singaporeans treated for conjunctivitis. It discusses the WHO (World Health Organization) Plan of Action for Eradication of Polio in the Western Pacific Region which includes Singapore.

Neonatal jaundice: update on phototherapy management

Phototherapy is now the standard form of treatment for infants with neonatal hyperbilirubinaemia. Though gradual in its effect, it finally produces a prolonged reduction in bilirubin values; retreatment with phototherapy is relatively rare. Factors that affect efficacy of phototherapy are: initial bilirubin level, birth weight, gestational age, postnatal age, aetiology of jaundice and light intensity and spectral emission. Phototherapy has now been demonstrated to be highly effective and safe; with simple precautions, no untoward side-effects will occur. The guidelines for commencement, monitoring and cessation of phototherapy are provided.

Efficacy of "high-intensity" blue-light and "standard" daylight phototherapy for non-haemolytic hyperbilirubinaemia

We report our clinical experience with phototherapy in 3802 infants; 3629 were exposed to "standard" daylight phototherapy and 173 to "high-intensity" blue-light phototherapy. High-intensity blue-light phototherapy was twice as effective as standard daylight phototherapy in decreasing bilirubin concentrations. No failures occurred with high-intensity phototherapy compared with an overall failure rate of 1.84/1000 with daylight lamps; these cases were transferred to high-intensity phototherapy with prompt response. Rebound after cessation of phototherapy was greater in those exposed to high-intensity blue light with a significantly greater number requiring a second exposure. However, the incidence was still low. No third exposure was required in any infant. Nursing of infants under high-intensity blue light was more difficult and inconvenient as was clinical monitoring. The light also caused more stress on the nursing and medical personnel. However, the infants tolerated both types of phototherapy equally well. High-intensity blue-light phototherapy would seem to be the treatment of choice for infants with rapidly increasing or very high bilirubin levels, as well as in those not responding adequately to daylight phototherapy.

Descriptive profile of birth defects among livebirths in Singapore

A case-control study of birth defects was carried out in Kandang Kerbau Hospital in Singapore for a three-year period from January 1986 until December 1988. This paper presents the descriptive profile of birth defects among livebirths seen in that hospital. Out of 44,842 livebirths, 678 babies were found to have birth defects, giving a prevalence of 15.13 per 1000 livebirths (95% CI 14.0-16.2). The musculoskeletal system was the most frequently affected system accounting for 161 cases with a prevalence of 3.59 per 1,000 livebirths (95% CI 3.06-4.19), followed by 111 cases with defects of the gastrointestinal system (2.47 per 1,000 livebirths 95% CI 2.04-2.98), 88 cases of chromosomal disorders (prevalence of 1.96 per 1,000 livebirths 95% CI 1.57-2.42), 78 cases with defects of the cardiovascular system (1.74 per 1,000 livebirths 95% CI 1.38-2.17), 73 cases with defects of the urogenital system (1.63 per 1,000 livebirths 95% CI 1.28-2.05), and 52 cases with defects of the central nervous system (1.16 per 1,000 livebirths 95% CI 0.87-1.52). The prevalence of cleft lip, cleft palate in isolation, and cleft lip and palate combined was 1.72 per 1,000 livebirths and the occurrence of Down's syndrome was 1 in 700 livebirths. When reviewed 6 weeks postpartum, the rate of false positives at birth was 4%. In a control group of 709 "normal" cases at birth, the rate of cases not detected at birth but detected at 6 week follow-up, false negatives was 0.84%.

Immunolabelling of prolactin at ultrastructural level using the protein A-gold technique on Epon-embedded tissue

The use of the colloidal-gold technique in electron microscopy immunocytochemistry has provided important information on the in situ localisation of intracellular antigens. We have developed a post-embedding technique for prolactin localisation on resin-embedded human pituitary tissue sections by the use of the protein-A gold conjugate. Human pituitary tissue obtained at autopsy was processed for electron microscopical study without post-osmication and then embedded in Epon. The indirect immunoperoxidase method was used for light microscopical targetting of lactotroph cells for subsequent electron microscopical antigen localisation. Ultra-thin sections were labelled with human anti-human prolactin followed by protein-A gold conjugate. Specific labelling was observed over secretory granules with a density of 15-30 particles per granule, as determined by the Quantimet 570 image analysis system. This technique provides a means of studying the pathophysiology of hormonal secretion at ultrastructural level and can be a useful tool in diagnostic and research investigations.

Phototherapy and the brain-stem auditory evoked response in neonatal hyperbilirubinemia

The latencies of peak V and interpeaks I-V and III-V in the brain-stem auditory evoked response of infants with hyperbilirubinemia before phototherapy were significantly greater than those in a control group of infants. These values of the brain stem auditory-evoked response improved significantly during phototherapy and correlated significantly with the declining bilirubin levels. Improvement continued after phototherapy, despite a rebound of serum bilirubin concentrations.

Phototherapy for ABO haemolytic hyperbilirubinaemia

The efficacy of 'standard' daylight phototherapy and 'high intensity' blue light phototherapy for neonatal jaundice from ABO-HD, or of a non-haemolytic nature was evaluated. Altogether 77 full-term infants with ABO-HD and 3,020 with non-haemolytic jaundice were studied. Both groups of infants responded well to standard daylight phototherapy; the response in non-haemolytic hyperbilirubinaemia was significantly greater. High intensity blue light phototherapy was significantly more effective in reducing bilirubin levels than standard daylight phototherapy in both group of infants with no failure being encountered. Four infants with non-haemolytic jaundice did not respond adequately to white light (1.4/1,000); they needed high intensity blue light for adequate response. Bilirubin rebound was mild. Four infants in the blue light group needed a second exposure (28.3/1,000) compared with 20 in the white light group (6.9/1,000), a difference that was significant. Standard white light phototherapy is usually adequate for ABO-HD as well as non-haemolytic hyperbilirubinaemia. High intensity blue light would be preferable where a more rapid and greater response is desirable.

Comparison of the immune response of four different dosages of a yeast-recombinant hepatitis B vaccine in Singapore children: a four-year follow-up study

The immunogenicity of four different dosages of yeast-derived hepatitis B vaccine (Merck, Sharp & Dohme: 0.6 micrograms, 1.25 micrograms, 2.5 micrograms and 5.0 micrograms), administered at 0, 1 and 6 months (0-1-6 schedule) intramuscularly, was evaluated in 122 seronegative healthy children 1-12 years of age. Three months after the first dose, 83.9-100% of the vaccinees seroconverted. Peak geometric mean titres (GMT) of between 1088 mlU/ml and 1699 mlU/ml were attained 3 months after completion of the vaccination schedule. After 24 months, anti-HBs (antibody to hepatitis B surface antigen) was detected in 93.1-100% of the vaccinees, but the GMT dropped to between 214.3 mlU/ml and 303.5 mlU/ml. After 48 months, 88.8-100% of the vaccinees continued to possess anti-HBs and 70.3-87% had titres above 10 mlU/ml. As expected, the GMT declined further to between 72.6 mlU/ml and 118.8 mlU/ml. There were no significant differences in seroconversion rates and GMT among the different dosage groups. All the vaccinees remained asymptomatic and free from hepatitis B virus infection. The study showed that reduced dosages of the vaccine (0.6 micrograms, 1.25 micrograms and 2.5 micrograms) were as immunogenic as the standard dose (5 micrograms); the 2.5-micrograms dose was recommended for the national childhood immunization programme in Singapore. No booster is necessary for at least four years after vaccination.

Phototherapy for neonatal jaundice

Phototherapy is now the preferred method of treatment for neonatal hyperbilirubinemia by virtue of its noninvasive nature and its relative freedom from major complications. It is also convenient, easy to use, and inexpensive in terms of personnel, equipment, and disposals. Long-term experience with phototherapy has demonstrated its safety as well as efficacy. With high-intensity phototherapy at saturation dose, even severe hemolytic hyperbilirubinemia can be adequately controlled; only pack-cell transfusions are required to correct the resulting anemia. It should be stressed, however, that adequate monitoring of the well-being of the baby together with the bilirubin levels should always be observed carefully. The lamps should be kept cool during phototherapy and be changed regularly after every 2000 hours of use. Observing such precautions will ensure the efficacy and safety of phototherapy.

Drug therapy of the fetus and neonate

The fetus and neonate are very sensitive and delicate. Events occurring during this period can therefore, have a very significant influence on later life. Drugs given to the pregnant women may have a significant impact on the fetus, as the thalidomide disaster has shown. Drug therapy of the fetus via the mother has also been proven to be effective in certain situations, especially with regard to improving lung maturity. With advances in visualisation of the fetus by ultrasonography, direct fetal treatment has been successfully performed. The neonate immediately after delivery is in a very precarious state, especially if premature. Drug therapy is sometimes indicated then to ensure his well-being. Such drug therapy will have to take into consideration absorption problems in relation to a prolonged gastrointestinal transit time as well as hepatic and renal immaturity, together with a relatively greater volume of distribution of the drug (Vd). When these considerations are taken into account, effective therapy can be instituted with successful results. Drug treatment for specific conditions in the premature baby, when tailored to their needs and limitations, have indeed been successful.