Hepatitis B in urban Australian schoolchildren. No evidence of horizontal transmission between high-risk and low-risk groups.

OBJECTIVE: To document the prevalence of hepatitis B virus (HBV) infection in urban Australian primary schoolchildren, and to look for evidence of horizontal transmission of HBV in schools between children at high risk of infection and those at low risk. We compared the prevalence of infection in a group of low-risk children attending control schools (less than 5% of students from high-risk groups) with the prevalence in low-risk children attending test schools (more than 20% of students from high-risk groups). METHODS AND RESULTS: Venous blood was collected and tested for hepatitis B markers by radioimmunoassay; 2883 children (1431 boys) of mean age 11.3 years (SD, 0.7) from 50 schools were tested. Evidence of past or current infection was present in 169 children (5.9%). This number comprised three of the 1347 low-risk children (0.2%), 10 of the 602 medium-risk children (1.7%), 154 of the 731 high-risk children (21.1%) and two of the 203 other children (1%). Fifty-four of the 169 infected children were hepatitis B surface antigen (HBsAg) positive, 36 of the 54 were also positive for hepatitis B e antigen (HBeAg). There was no difference between children in the low-risk group in test and control schools for markers of hepatitis B virus infection. CONCLUSIONS: A low prevalence of HBV infection was found in low-risk school-children irrespective of the proportion of high-risk children in their classes. Targeting vaccination to infants and children with known risk factors is the most important strategy in low endemicity countries; vaccination of children without risk factors could be delayed till early adolescence.

Optimal age for measles and mumps vaccination in Australia.

Trivalent measles-mumps-rubella vaccine has recently replaced measles-mumps vaccine in Australia and is recommended as a single dose at the age of 12 to 15 months, with the exception of Aboriginal children in central Australia who are vaccinated at 9 months. The timing of measles vaccination has been controversial not only in Australia but also in the United States, where measles outbreaks continue to occur. This study aimed to determine seroconversion rates for measles-mumps vaccine in children aged 12 to 18 months and to make a recommendation for the timing of vaccination based on seroconversion rates and attack rates. The parents of 425 children aged 12 to 18 months gave consent for their children to have serum collected at the time of measles-mumps vaccination and three months later. The mean age at vaccination of the children who had two serum samples for measles and mumps antibody estimations was 13.9 months (mode, 13.1). The seroconversion rate for measles was 95% (314/329) (95% confidence interval (CI), 92.5% to 97.3%) and for mumps 97% (309/320) (95% CI, 93.8% to 98.1%). There were no statistically significant differences in the rates of seroconversion for measles or mumps related to age in months at the time of vaccination or in post-vaccination measles antibody titres related to age at vaccination. Post-vaccination mumps antibody titres tended to be lower in older vaccinees. None of the children who presented for vaccination had serological evidence of prior measles infection but five had evidence suggestive of prior mumps. As the seroconversion rates for measles and mumps vaccines were very high in these children it was concluded that no advantage resulted from delaying vaccination until 15 months and that the current National Health and Medical Research Council recommendations for vaccination at age 12 to 15 months should remain.

Colloid and crystal formation in parotid saliva of cystic fibrosis patients and non-cystic fibrosis subjects. I. Physicochemistry.

Two types of turbidity were found in parotid saliva from both cystic fibrosis (CF) patients and non-CF subjects. On cooling saliva, a rapidly forming, reversible, cold-dependent turbidity appeared in increasing amounts with decreasing temperature and increasing protein concentration. At 37 degrees, a slowly forming, stable turbidity appeared in increased amounts in parotid saliva samples containing increased amounts of calcium. The 2 degree centrifuged pellet consisted predominantly of protein, whereas the 37 degree pellet contained calcium, inorganic phosphate, and protein. The cold-dependent turbidity at 2 degrees was not inhibited by EDTA, but 37 degrees turbidity was dramatically inhibited. Urea and guanidine hydrochloride reduced 2 degree turbidity, and, to a lesser extent, inhibited 37 degree turbidity. The tendency towards higher levels of protein, amylase, and calcium in CF compared with child control parotid saliva (4, 6) causes a greater incidence and degree of turbidity formation in saliva of CF patients. In this paper only the nature of the turbidity has been investigated, not its relative occurrence in each group of subjects.

Colloid and crystal formation in parotid saliva of cystic fibrosis patients and non-cystic fibrosis subjects. II. Electron microscopy and electrophoresis.

Centrifuged pellets of turbid parotid saliva from cystic fibrosis (CF) patients and non-CF subjects, obtained from saliva kept at 2 degrees for 10 min, had the electron microscope appearance of amorphous, round particles, and were thought to be colloidal aggregates of organic material. Drops of turbid saliva, from samples incubated for 2 hr at 2 degrees or 37 degrees, additionally contained discrete, electron-dense crystals having well defined angular morphology: usually cubic, retangular, or approximately hexagonal. The inhibitors, urea, guanidine hydrochloride, and EDTA, resulted in no crystals being observed. Selected area electron diffraction from individual crystals showed predominantly hexagonal, rectangular patterns could be indexed as coming from hydroxyapitite. A transition from the hexagonal to the rectangular pattern and back to the hexagonal pattern could be obtained from individual crystals tilted in the electron microscope. The square diffraction pattern may be from octa-calcium or brushite. Polyacrylamide gel disc electrophoresis of the parotid saliva indicated that the sparingly soluble proteins in the 2 degree and 37 degree pellets comprised proline-rich proteins and a calcium-precipitable, trichloroacetic acid (TCA)-precipitable phosphoprotein, which fluoresced with amido schwarz and Coomassie brilliant blue G250.

Parotid gland function in children with cystic fibrosis and child control subjects.

Parotid saliva was collected from 22 children with cystic fibrosis (CF) and 21 control children. Stimulation was by 0.1 ml 5% citric acid on the tongue every 15 sec over a period of 10 min, and samples were collected for 2-min intervals. Stimulated saliva showed a lag period of low amylase release, and an activated period of higher amylase release. The major difference between CF and child control parotid saliva was in the elevated calcium concentrations in CF subjects. Flow rate and amylase, although higher in the CF group, were not raised to a statistically significant level. There were higher mean values for sodium and inorganic phosphate in CF children but statistical significance was minimal. Potassium values were almost identical in CF and control saliva. In the activated parotid saliva samples of both control and CF subjects there were positive correlations between flow rate and calcium, flow rate and sodium, anylase and calcium, and sodium and calcium, and negative correlations between sodium and potassium. The parotid function test has no value as a diagnostic test for cystic fibrosis, as even calcium values show too much overlap with control saliva to be of diagnostic worth.