A study in rural Kenya, over a 4-year period following the introduction of the 10-strain pneumococcal conjugate vaccine for infants, that included a catch-up vaccination campaign for children 12-59 months of age, suggests that the catch-up vaccination for older birth cohorts may have been a key factor in protecting unvaccinated individuals and speeding up the reduction of the disease in the community. In contrast, a study in The Gambia, where no catch-up campaign took place, found no herd effects during the first three years following the introduction of PCV-13 for infants.
The Gambia study publication referenced can be found at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4909992/
A study of the 10-strain pneumococcal conjugate vaccine in rural Kenya demonstrated herd protection. Over a 4-year period following the introduction of the vaccine for infants, coupled with a “catch-up” campaign for all children 12-59 months of age, the incidence of invasive pneumococcal disease (IPD) caused by the strains in the vaccine fell by 100% in infants less than two months of age who were too young to be vaccinated. In adults (≥ 15 years old) the incidence of IPD fell by 81% and in 5-14 year olds the incidence fell by nearly 75%. The chances of unvaccinated persons becoming ill with any strain of the disease also fell significantly – by 87% in infants under two months old, by nearly half (47%) in 5-14 year olds, and by more than one-third (37%) in adults.
One of the first studies of real-world use of pneumococcal conjugate vaccine (PCV) in Africa, found 48% fewer cases of pneumonia in children confirmed by x-ray after PCV introductoin. The results show the vaccine greatly reduced childhood pneumonia hospital admissions in Kenya: Hospital admissions for pneumonia went down 27%.The vaccine led to 329 fewer pneumonia cases per 100,000 kids each year.
A systematic review of studies from countries in Africa and Southeast Asia investigated the relationship between a woman’s “agency” (defined as the woman’s ability to state her goals and to act upon them with motivation and purpose) and childhood immunizations in lower-income settings. The review found a general pattern among studies in which higher agency among mothers was associated with higher odds of childhood immunizations. Empowering women in these settings shows promise as a means to improve child health.
In a systematic review of qualitative research from low- and middle-income countries, women’s low social status was shown to be a barrier to their children accessing vaccinations. Specific barriers included access to education, income, resource allocation, and autonomous decision-making related to time. The authors suggest that expanding the responsibility for children’s health to both parents (mothers and fathers) may be one important element in removing persistent barriers to immunization often faced by mothers.
An analysis of the impact of rotavirus vaccine in 25 countries found that the rates of vaccination in all countries were highest and risk mortality lowest in the top two wealth quintile’s coverage. Countries differed in the relative inequities in these two underlying variables. Cost per DALYs averted in substantially greater in the higher quintiles. In all countries, the greatest potential vaccine benefit was in the poorest quintiles; however, reduced vaccination coverage lowered the projected vaccine benefit.
A systematic literature review analyzing data from 21 African countries revealed that bacterial meningitis is associated with high case fatality and frequent neurophysiological sequelae. Pneumococcal and Hib meningitis contribute to one third of disease related mortality. They also cause clinically evident sequalae in 25% of survivors prior to hospital discharge. The three main causes of bacterial meningitis- Haemophilus influenzae type B; Streptococcus pneumoniae (pneumococcus) and Neisseria meningitidis (meningococcus) are vaccine preventable, routine use of conjugate vaccines have potential for significant health and economic benefits.
Neuropsychological sequelae includes hearing loss, vision loss, cognitive delay, speech/language disorder, behavioural problems, motor delays/impairment, and seizures.
In a systematic literature review of studies in Africa, it was found that 25% of children who survived pneumococcal or Hib meningitis had neuropsychological deficits.
A prospective case-control study conducted in several developing countries found that children with moderate-to-severe diarrhea grew significantly less in length in the two months following their episode compared to age- and gender-matched controls.
A study in Kenya revealed that immunization with polio, BCG, DPT and measles had protective effects with respect to stunting in children under 5 years of age. In children under the age of 2 years, immunized children were 27% less likely to experience stunting when compared to unimmunized children. Additionally, children who suffered from cough or diarrhea in the 2 weeks prior to the study showed an 80-90% higher probability of being underweight or experiencing wasting.
