BackgroundNomadic lifestyle has been shown to be a significant factor in low immunization coverage. However, other factors which might aggravate vaccination uptake in nomadic pastoralists are poorly understood. Our study aimed at establishing the relative influence of social demographics, missed opportunities, and geographical mobility on severe under vaccination in children aged less than two years living in a nomadic pastoralist community of Kenya.MethodsWe used cross-sectional analytical study design. An interviewer-administered questionnaire was used to obtain quantitative data from 515 mothers with children aged less than two years. Under vaccination was the sum the total number of days a delayed vaccine was given after the recommended age range for each vaccine. Severe under vaccination was defined as those children who remained under-vaccinated for more than six months. Geographical mobility was assessed as household members who had gone to live or herd elsewhere in the previous 12 months, missed opportunity included questions on whether a child visiting a health facility had missed being vaccinated, while social demographic data included household size and mothers social demographics.ResultsThree-quarters of the mothers had no formal education. One-third of the children had been taken to a health facility and missed being vaccinated. Forty percent of the households had moved in the previous 12 months. Prevalence of missed opportunity was 30.1%; 42.2% of children had not received any vaccines by their first birthday, and 24.1% of children were severely under vaccinated.No significant association was found between social demographics and under-vaccination. Variables associated with under-vaccination were; movement of the whole family, (p = .015), missed opportunity, (p = <.001), lack of vaccines, (p = (.002), and location of health facility, (p = <.001). Movement of women and children made a significant contribution (p = 0.006) to severe under-vaccination. Children in households where women and children had moved were nine times more likely to be severely under-vaccinated than in those households where there was no movement.ConclusionGeographic mobility of women and children was a key determinant of severe under vaccination among nomadic pastoralists in Kenya.

Background: Children from nomadic pastoralist communities might not receive all the recommended doses of vaccines at age-appropriate times due to limited access to immunization services.  Skipped, delayed or missed vaccination doses result in under vaccination which in turn make children vulnerable to preventable diseases.  The purpose of present study was to establish completion timeliness and under-vaccination of all the recommended childhood vaccinations in a nomadic pastoralist community.Methods: Authors used a cluster sampling technique to identify children aged 0 to 24 months at the household level.  Vaccine completion was the accumulation of the required number of doses by infants irrespective of the timing. Timeliness was vaccines administered within the recommended age range. Under vaccination was the sum total of days a delayed vaccine was given after the recommended age range.Results: Completion of all individual antigens did not meet the target of 90%. The mean number of days a child remained under-vaccinated in days was: OPV0, 20 days; BCG, 39 days; measles vaccine, 47 days; PVC3, 121 days; pentavalent, 117 days, and rotavirus, 103 days.  Approximately 42% were severely under-vaccinated for more than six months. Vaccine-specific under-vaccination of more than six months was:  pentavalent 3, 20%; PCV 3, 14%; OPV 3, 9.5%; BCG, 3%, and measles vaccine 20%. Overall children remained under-vaccinated for 185 days.Conclusions: A significant proportion of children remained under vaccinated for extended periods leaving them at risk during a vulnerable period of their life.

In the present work, a theoretical study of the variation of the photoionization cross-section with the incident photon frequency and the axial position of a hydrogenic donor impurity in GaAs quantum well dot of square cross-section is carried out. In the calculation, a trial wave function in the effective mass approximation and a finite potential well is used. The wave function is constructed with an appropriate envelope wave function that satisfies the boundary conditions, i.e., the wave function vanishes at the boundary. A trial wave function is employed to calculate the total energy of the hydrogenic donor impurity in the ground state. The total energy is then minimized with respect to the variational parameter in the trial wave function to obtain the minimum energy. The minimized total energies are then used to determine the donor binding energies within the quantum dot. It is observed that for a quantum dot of constant cross-section, the binding energy increases with a decrease in dot length to a peak value; thereafter it decreases rapidly towards zero. The binding energies obtained are used to compute the photoionization cross-section of the hydrogenic donor impurity as a function of the incident photon frequency for different positions of the donor impurity. It is observed that the photoionization cross-sections rise steeply to their peaks from almost zero value then gradually decrease as the photon frequency increases until they become almost constant for very high photon frequencies. The photoionization cross-section peak is much higher for the hydrogenic donor impurity located closest to the centre of the quantum well dot than for donor impurity located farther away from the dot centre. This indicates that the photoionization cross-section is sensitive to the location of the donor impurity in the quantum dot and to the incident photon frequency.