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Biomedical subjects

G T Stewart

Publications and source records attributed to G T Stewart.

At least 19 recordsLinked to original sources
PubMed1979

A healthy start.

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Developing Countries↗
PubMed1979

A mathematical model of a heroin epidemic: implications for control policies.

An exponential model based on the infectious disease model of Kermack and McKendrick has been simplified to illustrate how the use of heroin spreads in epidemic fashion. A numerical simulation is arranged to show how the dynamics of spread are influenced by the original number of users, rates of conversion, and time of removal from the drug scene of those secondarily affected. The spread is significantly increased by small increases of those originally affected, in which case reduction of spread requires a large increase in rate of removal. The model indicates a strategy for intervention which is discussed in relation to policies for control of drug abuse.

Disease Outbreaks↗
PubMed1979

Infection and immunization.

Herd infections, especially in children, are strongly influenced epidemiologically by social and demographic factors which have contributed favorably to a general decline in incidence and mortality during the past 50 years or more. Intervention procedures such as immunization cannot be evaluated or planned realistically except against these background factors. Assessed in this way, immunization against diphtheria and poliomyelitis was unequivocally effective in reducing incidence and morbidity of these diseases. By comparison, pertussis vaccine has a very limited protective effect, the value of which, as morbidity decreases, may be offset by the intrinsic toxicity of the vaccine and by the possibility of infrequent but severe brain damage in some children.

Adolescent↗
PubMed1977

Vaccination against whooping-cough. Efficacy versus risks.

Calculations based on the mortality of whooping-cough before 1957 predict accurately the subsequent decline and the present low mortality. Notifications of incidence, though variable and incomplete, follow the same pattern of steady decline in the United Kingdom and are unaffected either by small-scale vaccination beginning about 1948 or by nationwide vaccination beginning in 1957. When valid comparisons can be made, attack-rates may be lower and complications fewer in vaccinated children, but allowance has to be made for overcrowding and socio-economic differences which may be more important as determinants of attack-rates. No protection by vaccination is demonstrable in infants. Adverse reactions and neurotoxicity following vaccinations were studied in 160 cases. In 79, the relationship to pertussis vaccine was strong. In 14 of these cases, reaction was transient but characteristic of a syndrome of shock and cerebral disturbance, which, in the other 65 cases, was followed by convulsions, hyperkinesis, and severe mental defect. It seems likely that most adverse reactions are unreported and that many are overlooked. Precise information about the efficacy and safety of this vaccine is lacking, because existing provisions, national and international, for epidemiological surveillance and evaluation are inadequate. The claim by official bodies that the risks of whooping-cough exceed those of vaccination is questionable, at least in the U.K.

Adolescent↗
PubMed1976

Epidemiological evaluation of immunisation and other factors in the control of whooping-cough.

The general incidence of whooping-cough is lower in fully immunised children, but present immunisation schedules do not adequately protect the infant below 1 year of age either from contracting infection or from its complications. In a recent outbreak in Glasgow, nearly one-third of notified cases were fully immunised. In Glasgow and probably in the U.K. as a whole, the persistance of whooping-cough in some areas is more strongly correlated with adverse socio-economic conditions that with lack of immunisation. The decline in recent years could be attributable to improvement in these conditions at least as much as to immunisation. There is no epidemiological justification for continuing mass immunisation, but there is a strong case for an intensified eradication policy which might include selective immunisation in high-risk groups and areas.

Adolescent↗