Rubella vaccination policy: a note of caution.
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Child↗
Biomedical subjects
D J Nokes
Publications and source records attributed to D J Nokes.
Rubella epidemiology in South East England.
Analyses of data collected in a large survey (sample size greater than 3000) of rubella antibody in South East England, finely stratified according to age, reveal age-dependent changes in the pattern of virus transmission. The rate or force of infection changes from low in the young children to high in the 5- to 15-year-olds and back to low again in the adult age classes (there is a 50% reduction between the 5- to 15-year-olds and the 20+-year-olds). Raised levels of immunity are recorded in the teenage and young adult female segments of the population as a consequence of the UK rubella immunization programme. Mean antibody concentrations show a decline with age and are, on average, lower in vaccinated females when compared with unvaccinated males of the same age. The interpretation of horizontal cross-sectional serological data and future research needs are discussed.
Adolescent↗
Immunization in the developing world: strategic challenges.
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Adolescent↗
Salivary antibody detection in epidemiological surveys: a pilot study after a mass vaccination campaign against rubella in São Paulo, Brazil.
The sensitivity and specificity of salivary rubella antibody detection was investigated using samples collected from 301 children after a mass vaccination campaign in the state of São Paulo, Brazil. Saliva samples were collected by 2 different methods: directly dribbling into a container or using a commercial collecting device. Corresponding finger-prick blood samples were collected on filter paper. Rubella specific immunoglobulin G (IgG) was measured in saliva by antibody capture radioimmunoassay and in blood samples by indirect enzyme-linked immunosorbent assay. The detection of salivary rubella specific IgG showed good correlation with the detection of rubella antibody in the blood samples. For both collecting techniques the predictive value for a positive saliva test was > 99% compared with the results from the blood tests. However, the predictive value for a negative saliva test was only 58.3% for a dribbled sample, compared to 100% for saliva collected using the commercial device. Moreover, collecting saliva by dribbling from children less than 4 years old was difficult. The detection of rubella specific IgG in saliva collected using a commercial device proved to be sensitive and specific in this epidemiological study, encouraging its more widespread application as a means of surveillance after mass vaccination.
Adolescent↗
Maternal rubella-specific antibody prevalence in Ethiopian infants.
In countries with a high transmission rate of rubella the optimal age for universal rubella vaccination of infants is critically dependent upon the rate of loss of maternal antibodies. Few studies have investigated the decay characteristics of such antibodies. Mother:infant pairs were recruited at the Ethio-Swedish Children's Hospital, Addis Ababa, in 1994/95. Rubella antibody levels, determined by radial haemolysis, were available for analysis from 1542 infants aged 0-12 months, with 942 repeat measures, and from 846 mothers. Decay in seropositivity was well described by a delayed exponential function. The proportion seropositive at age 6, 9, or 12 months was 6-13%, 1-4%, or 0-1%, respectively, dependent upon assay cutoff level. Only infant age and mother's antibody level were important predictors of seropositivity. Results suggest that the success of vaccination at age 9 months or above would be little affected by residual maternal antibodies.
Adult↗
Vaccination against hepatitis B virus in highly endemic areas: waning vaccine-induced immunity and the need for booster doses.
A dynamic model of the transmission of hepatitis B virus (HBV) was used to investigate some of the possible implications of the loss of vaccine-induced immunity on the effectiveness of mass HBV vaccination in high endemicity countries. The model, which describes the processes of horizontal and vertical transmission of HBV in a rapidly growing population, was based on one previously published, modified to allow for waning vaccine-induced immunity. All model parameters were empirically based. Summaries of published data provided estimates of the mean duration of immunity in vaccine responders and age-dependence in the risk of developing acute HBV disease. Simulations of the temporal and long-term impact of mass infant immunization on the prevalence of HBV chronic carriage and acute disease suggested that booster doses are of little benefit in coping with waning vaccine protection. The key factor is that vaccine-induced protection should be long enough to prevent infection in the first few years of life, when the risk of developing chronic carriage is highest.
Acute Disease↗
Measles antibody levels in a vaccinated population in Brazil.
An epidemiological study of measles-specific immunoglobulin G antibody levels was conducted using a representative sample of a vaccinated suburban population in São Paulo State, Brazil. The study aimed to determine immunity status in relation to age and infection or vaccination experience. 549 age-structured samples of sera, collected in 1990, were screened and calibrated to the international reference serum, using measles nucleoprotein in an enzyme immunoassay. In the age group with direct experience of vaccination (9 months to 15 years), whether routine or campaign, over 90% had detectable antibody > or = 50 miu/mL. However, 14% of these had antibody concentrations between 50 and 100 miu/mL and 30% between 50 and 255 miu/mL. In those over 15 years of age, 94% had antibody levels > 255 miu/mL, assumed to be the result of past infection. The study suggested that, within highly vaccinated populations, a proportion of individuals had measles antibody levels which may be insufficient to protect against reinfection or clinical disease. The implications of these results, and similar findings elsewhere, in relation to the persistence of measles requires investigation; this has particular relevance in São Paulo following the recent measles outbreak.
Adolescent↗
An evaluation of oral-fluid collection devices for the determination of rubella antibody status in a rural Ethiopian community.
We compared 3 different oral-fluid collection devices to assess their suitability for use in community studies of rubella antibody. Of 58 individuals enrolled from 13 households from a southern Ethiopian village, 38 provided a blood sample and oral fluids by the 3 devices: 2 proprietary, Omni-SAL and OraSure, and a third a polystyrene sponge swab (Sponge). The Sponge swab, used like a toothbrush, was most acceptable to survey staff and to participants of all ages, although it proved ill-adapted for fluid extraction. The other devices more often caused participant discomfort or anxiety, particularly in the young. Statistical comparison of rubella-specific immunoglobulin (Ig) G in oral fluid, measured by antibody-capture radioimmunoassay, and in serum, by indirect enzyme-linked immunosorbent assay, showed no clear differences between the devices in oral-fluid performance. Specificity range was 75-100% and sensitivity 73-85%, relative to serum. Specific-antibody levels declined with increasing age, with concomitant decreases in sensitivity, as previously documented. The relationship between specific IgG and total IgG in oral fluid differed by device. Specific IgG levels were highly correlated between paired samples using the Sponge device. We consider the Sponge device to be the most suitable for community survey work, although the extraction method requires improvement. Further work is needed to improve the sensitivity of antibody status determination in adults.
Adolescent↗