Vaccine-preventable disease and immunization in the developing world

Incidence of infant mortality and its predictors in East Africa using Gompertz gamma shared frailty model

Background

Globally, infant mortality is a major public health concern and a sensitive indicator of countries' socio-economic and health status. Despite the substantial reduction of under-five mortality in sub-Saharan African countries specifically in East Africa, the infant mortality rate remains highest and too far below to achieve the WHO target. As to our search of the literature is concerned, there is a dearth of evidence on the incidence and predictors of infant mortality in East Africa. Therefore, this study investigated the incidence of infant mortality and its predictors in East Africa.

Methods

The present study has utilized 138,803 weighted samples from Demographic and Health Surveys (DHSs) of 12 East African countries. Considering the hierarchical nature of DHS data shared frailty parametric survival models were fitted and compared based on deviance (-2LLR), AIC, and BIC. Gompertz gamma shared frailty model was the best-fitted model for the data since it had the lowest deviance, AIC, and BIC values. Variables with a p-value < 0.2 in the bi-variable analysis were considered for the multivariable analysis. In the multivariable Gompertz gamma shared analysis, the Adjusted Hazard Ratio (AHR) with 95% Confidence Interval (CI) was reported to declare the significant predictors of infant mortality.

Results

The infant mortality rate in East Africa was 41.41 per 1000 live births. Mothers aged 25–34 years, wanted birth, health facility delivery, 1–3 ANC visit, being 2nd- 4th birth order, 5th and above, the birth interval of 24–48 months, and birth interval of 49 months and above were significantly associated with lower risk of infant mortality. Whereas women who didn’t have formal education, women who didn't participate in making health care decisions making, being male children, cesarean delivery, small size at birth, and large size at birth were significantly associated with a higher risk of infant mortality.

Conclusion

Despite the substantial progress in improving maternal and child health, this study showed that infant mortality is still a major public health concern in East Africa. Maternal age, place of delivery, maternal education, birth size, sex of the child, mode of delivery, women's autonomy, birth order, birth interval, and ANC visit were found to be significant predictors of infant mortality. Therefore, public health interventions enhancing health facility delivery, ANC visit, maternal education, birth spacing, and empowering women are crucial for reducing the incidence of infant mortality in East Africa.

Immunogenicity and safety of four different doses of Haemophilus influenzae type b-tetanus toxoid conjugated vaccine, combined with diphtheria–tetanus–pertussis vaccine (DTP-Hib), in Indonesian infants

Widespread use of Haemophilus influenzae type b (Hib) conjugated vaccine in industrialized countries has resulted in a dramatic decline in the incidence of invasive Hib diseases, but the vaccine's cost has prevented its inclusion in basic immunization programs in developing countries. To overcome this problem, combination with diphtheria-tetanus-pertussis (DTP) vaccine or reduction in the dose of Hib vaccine has been proposed. To evaluate the immunogenicity and adverse reactions from lower doses of Hib-polyribosylphosphate (PRP) conjugated with tetanus toxoid (PRP-T), a double-blind study was conducted in Jakarta, Indonesia, and its suburbs. A total of 1048 infants 6 weeks to 6 months of age received three doses of DTP vaccine combined with the usual 10 microg dose or with a reduced dose of 5, 2.5 or 1.25 microg of PRP-T at two-monthly intervals. Antibodies were measured prior to the first dose and 4-6 weeks following the third dose. Adverse reactions were similar among all four groups. The only significant difference was a higher rate of irritability (p<0.02) and of temperature elevation >38 degrees C (p<0.009) after doses 1 and 2 in the lowest dose group (1.25 microg PRP-T) compared to the other groups. All participants tested had a 4-fold increase in antibodies against all DTP antigens. In addition, after a fourth booster dose of Hib, 99.6% of infants produced >or=0.15 microg/ml of antibody to Hib-PRP, and 96.4% showed levels >or=1.0 microg/ml after primary immunization, level that correlate with short- and long-term immunity, respectively. Antibody titers to the PRP antigen showed no significant differences among dosage groups with the exception of the 5.0 microg group, which had a significantly higher GMC than the 1.25 microg group (p<0.012). This study demonstrates that primary vaccination with half, one-fourth, or one-eighth of the usual dose of PRP-T, combined with DTP vaccine, produces protective immune responses, and has side effects that are comparable to DTP vaccination alone. In these lower dosages, PRP-T conjugate vaccine can lower vaccine costs to a level that is affordable for infant immunization programs in developing countries.

Vaccines and infectious disease

The exponential growth in vaccine research over the last decade, in which many infectious diseases now appear to be amenable to prevention through immunization, is built upon three factors: first, a richer understanding of the immune response (in particular, cellular immunity), second, a greater finesse in understanding the molecular biology of pathogenicity, and third, an expanding use of genetic engineering techniques either to create micro-organisms of greatly attenuated virulence that may be used as vaccines, or to sequence, and express, potential vaccine antigens. With respect to vaccines composed of purified antigens, parallel work is underway to develop immuno-modulating agents (adjuvants) that will selectively and safely induce the necessary immune response. Finally, within this plethora of vaccine candidates, vaccinologists are devoting much effort to alternatives to immunization via injection, such as administration of a vaccine through the mucosal route (e.g., oral, intranasal, intravaginal, etc.), through the transcutaneous route, and even by expression of vaccine antigens in edible fruits and vegetables.

Botulinum versus tetanus neurotoxins: why is botulinum neurotoxin but not tetanus neurotoxin a food poison?

Botulinum and tetanus neurotoxins, produced by Clostridium botulinum and Clostridium tetani, respectively, are the most poisonous poisons known to mankind. Although botulinum and tetanus neurotoxins share several characteristics, such as similar mol. wts, similar macrostructure, virtually identical mode of action, and a strong amino acid sequence homology, the two neurotoxins differ in one very significant way; only botulinum neurotoxin is a food poison. Factors responsible for the food poisoning potential of botulinum neurotoxins seem to be a group of complexing proteins that are also produced by C. botulinum, and are known to associate with the neurotoxin. Translation products of nucleotide sequences upstream to the neurotoxin genes of serotypes A, B, C, D, E and F botulinum neurotoxin reveal the location of genes for one of the complexing proteins that could be transcribed as polycistronic mRNA to include neurotoxin sequences. No such protein seems to be present in C. tetani, suggesting that the lack of complexing proteins might be responsible for tetanus not being a food poison.

Intimidation, coercion and resistance in the final stages of the South Asian Smallpox Eradication Campaign, 1973-1975

This paper reviews episodes during 1973-1975 when American physician-epidemiologists in South Asia, working under the auspices of the World Health Organization, intimidated local health officials and resorted to coercive methods in the final stages of the Smallpox Eradication Programme. While intimidation and coercion were successful in the short-run in ensuring disease containment, they evoked health-professional and popular resentments, and the long-term effect may have been to foster negative attitudes toward subsequent vaccination campaigns. At the very least these episodes suggest a need for paying attention to actual and perceived abuses when global health measures are introduced from 'above' into regional settings.

Molecular biology of rubella virus

This chapter summarizes the present medical significance of rubella virus. Rubella virus infection is systemic in nature and the accompanying symptoms are generally benign, the most pronounced being a mild rash of short duration. The most common complication of rubella virus infection is transient joint involvement such as polyarthralgia and arthritis. The primary health impact of rubella virus is that it is a teratogenic agent. The vaccination strategy is aimed at elimination of rubella and includes both universal vaccination of infants at 15 months of age with the trivalent measles, mumps, rubella (MMR) vaccine and specific targeting with the rubella vaccine of seronegative women planning pregnancy and seronegative adults who could come in contact with women of childbearing age, although it is recommended that any individual over the age of 12 months without evidence of natural infection or vaccination be vaccinated. Medically, the current challenge posed by rubella virus is to achieve complete vaccination coverage to prevent resurgences.

Electroencephalogram and evoked potentials in the primate model of viral encephalitis

Squirrel monkeys with induced canine distemper virus (CDV) encephalitis showed characteristic clinical signs such as seizures or myoclonus, with EEGs showing periodic synchronized discharge (PSD). Histopathologically, there was gliosis and neuronal degeneration diffusely distributed in both the gray and white matters in the subacute phase, the lesions resembling those found in childhood acute viral encephalitis and subacute sclerosing panencephalitis (SSPE). The auditory brain-stem response (ABR) changes were remarkable in the subacute phase, and the recovery of latency was correlated with survival. The visual evoked potential (VEP) abnormalities disappeared in the acute phase and appeared again with delayed latency in the subacute stage. One monkey which did not show clinical signs but had the pathological changes showed the VEP abnormality. These data suggest that the evoked potentials are helpful in judging the prognosis, and that this model is useful for the analysis of the pathogenesis of viral encephalitis.