OBJECTIVE: To compare estimates based on vaccination cards, parental recall, and medical records of the percentages of children up-to-date on vaccinations for diphtheria, tetanus, and pertussis; polio; and measles, mumps, and rubella. METHOD: The authors analyzed parent interview and medical records data from the Baltimore Immunization Study for 525 2-year-olds born from August 1988 through March 1989 to mothers living in low-income Census tracts of the city of Baltimore. RESULTS: Only one-third of children had vaccination cards; based on medical records, these children had higher up-to-date coverage at 24 months of age than did children without cards. For individual vaccines, only two-thirds of parents could provide information to calculate coverage rates; however, almost all provided enough information to estimate coverage for the primary series. For each vaccine and the series, parental recall estimates were at least 17 percentage points higher than estimates from medical records. For children without vaccination cards whose parents could not provide coverage information, up-to-date rates based on medical records were consistently lower than for children with cards or with parents who provided coverage information. CONCLUSIONS: Population-based vaccine coverage surveys that rely on vaccination cards or parental recall or both may overestimate vaccination coverage.
A challenge facing immunization registries is developing measures of childhood immunization coverage that contain more information for setting policy than present vaccine series up-to-date (UTD) rates. This study combined milestone analysis with provider encounter data to determine when children either do not receive indicated immunizations during medical encounters or fail to visit providers. Milestone analysis measures immunization status at key times between birth and age 2, when recommended immunizations first become late. The immunization status of a large population of children in the Oregon ALERT immunization registry and in the Oregon Health Plan was tracked across milestone ages. Findings indicate that the majority of children went back and forth with regard to having complete age-appropriate immunizations over time. We also found that immunization UTD rates when used alone are biased towards relating non-UTD status to a lack of visits to providers, instead of to provider visits on which recommended immunizations are not given.
The objective of this study was to understand how low income, inner-city parents of preschool children think about childhood diseases and prevention and the impact that this has on late receipt of vaccines.
Parents of all children born between 1/1/91 and 5/31/95, whose child received medical assistance and their health care at one of four inner-city, primary care clinics in Pittsburgh, PA., completed a telephone interview and gave consent for a vaccine record review. The main outcome measures were lateness for first and third diphtheria and tetanus toxoids and pertussis vaccines (DTP) and not receiving at least 4 DTP, 3 polio virus containing and 1 measles, mumps and rubella (MMR) doses by 19 months.
483 parents participated. Fifteen percent of children were late for the first DTP, 52% for the third DTP and, 40% had not received at least 4 DTP, 3 polio and 1 MMR by 19 months of age. Statistically significant factors associated with lateness at 19 months included: having three or more children, having two children, beliefs regarding the severity of immunization side effects and, being African American.
The results of this study indicate that a combination of life circumstances as well as cognitive factors were associated with late immunization.
Immunization behavior; parental beliefs; health communication; health behavior; health disparities
OBJECTIVE: The objective of this study was to understand how low income, inner-city parents of preschool children think about childhood diseases and prevention and the impact that this has on late receipt of vaccines. METHODS: Parents of all children born between January 1, 1991, and May 31, 1995, whose child received medical assistance and health care at one of four inner-city, primary care clinics in Pittsburgh, PA, completed a telephone interview and gave consent for a vaccine record review. The main outcome measures were lateness for first and third diphtheria and tetanus toxoids and pertussis vaccines (DTP) and not receiving at least four DTP, three polio virus containing and one measles, mumps and rubella (MMR) doses by 19 months. RESULTS: A total of 483 parents participated. Fifteen percent of children were late for the first DTP, 52% for the third DTP, and 40% had not received at least four DTP, three polio and one MMR by 19 months of age. Statistically significant factors associated with lateness at 19 months included: having three or more children, having two children, beliefs regarding the severity of immunization side effects, and being African American. CONCLUSIONS: The results of this study indicate that a combination of life circumstances, as well as cognitive factors were associated with late immunization.
OBJECTIVE: To estimate the risk factors of children experiencing delay in age-appropriate vaccination using a nationally representative population of children, and to compare risk factors for vaccination delay with those based on up-to-date vaccination status models. METHODS: The authors compared predictors of delay in age-appropriate vaccination with those for children who were not up-to-date, using a nationally representative sample of children from five years of pooled data (1992-1996) from the National Health Interview Survey (NHIS) Immunization Supplement. Duration of delay was calculated for the DTP4, Polio3, MMR1 doses and 4:3:1 series using age-appropriate vaccination standards; up-to-date status (i.e., whether or not a dose was received) was also determined. Adjusted odds ratios were estimated using multivariate logistic regression for models of vaccination delay and up-to-date vaccination status. RESULTS: Absence of a two-parent household, large family size, parental education, Medicaid enrollment, absence of a usual provider, no insurance coverage, and households without a telephone were significantly related to increased odds of a child experiencing vaccination delay (p < or = 0.05). CONCLUSIONS: Many of the risk factors observed in models of vaccination delay were not found to be significant in risk models based upon up-to-date status. Consequently, risk models of delays in age-appropriate vaccination may foster identification of children at increased risk for inadequate vaccination. Populations at increased risk of inadequate vaccination can be more clearly identified through risk models of delays in age-appropriate vaccination.
Studies from low-income countries have suggested that diphtheria-tetanus-pertussis (DTP) vaccine provided after Bacille Calmette-Guerin (BCG) vaccination may have a negative effect on female survival. The authors examined the effect of DTP in a cohort of low birthweight (LBW) infants.
2320 LBW newborns were visited at 2, 6 and 12 months of age to assess nutritional and vaccination status. The authors examined survival until the 6-month visit for children who were DTP vaccinated and DTP unvaccinated at the 2-month visit.
Two-thirds of the children had received DTP at 2 months and 50 deaths occurred between the 2-month and 6-month visits. DTP vaccinated children had a better anthropometric status for all indices than DTP unvaccinated children. Small mid-upper arm circumference (MUAC) was the strongest predictor of mortality. The death rate ratio (DRR) for DTP vaccinated versus DTP unvaccinated children differed significantly for girls (DRR 2.45; 95% CI 0.93 to 6.45) and boys (DRR 0.53; 95% CI 0.23 to 1.20) (p=0.018, homogeneity test). Adjusting for MUAC, the overall effect for DTP vaccinated children was 2.62 (95% CI 1.34 to 5.09); DRR was 5.68 (95% CI 1.83 to 17.7) for girls and 1.29 (95% CI 0.56 to 2.97) for boys (p=0.023, homogeneity test). While anthropometric indices were a strong predictor of mortality among boys, there was little or no association for girls.
Surprisingly, even though the children with the best nutritional status were vaccinated early, early DTP vaccination was associated with increased mortality for girls.
In many Tennessee counties, children under the care of health departments have low measles vaccination levels. An immunization survey and a health department record audit of 2-year-olds were undertaken in two counties to determine the reasons for this situation. The results indicated that faulty clinic procedures played a large part in the failure to vaccinate against measles. Nearly half of the unvaccinated 2-year-olds with health department records had been present in the health department clinic at the appropriate age for measles vaccination; the remainder had dropped out of the well-child program before their first birthday. Emphasis on tuberculin skin testing and delay in the administration of the basic series of DTP immunizations correlated with the failure to vaccinate against measles. For more than half of the children who attended the clinic after their first birthday, no reason was recorded for the failure to vaccinate them against measles. Improved clinic procedures could bring measles vaccination levels within the acceptable range. These procedures would include new methods for correcting immunization delinquency, simultaneous tuberculin skin testing and measles vaccination of children without a history of tuberculosis exposure, emphasis on vaccinating at-risk groups, and more convenient vaccination clinic hours.
OBJECTIVE: This study assessed the timeliness of immunization for children in a Medicaid managed care primary care case management program controlling for patient and provider predictors of immunization status. METHODS: Using administrative data and patient medical records, up-to-date (UTD) and age appropriate immunization (AAI) status were reviewed for 5598 children. The 4:3:1 immunization series (four diphtheria, pertussis, tetanus vaccinations; three polio vaccinations; and one measles, mumps, rubella vaccination) was the standard. RESULTS: Childhood immunization rates were low when assessed using strict adherence to vaccination recommendations. At age 18 months, 28.3% were classified as UTD, and 6.3% were classified as AAI. Compared to children not up-to-date, UTD children were more likely to have public rather than private providers, to have had older mothers, and less likely to have been African American. Among UTD children, AAI children were more likely to reside in urban areas. CONCLUSIONS: Low-income children continue to be under-immunized, even under a managed care initiative. Health care providers and child health advocates need to continue pressure for programs that will increase adherence to nationally recommended guidelines.
This study assessed the timeliness of immunization for children in a Medicaid managed care primary care case management program controlling for patient and provider predictors of immunization status.
Using administrative data and patient medical records, up-to-date (UTD) and age appropriate immunization (AAI) status were reviewed for 5,598 children. The 4:3:1 immunization series (4 diphtheria, pertussis, tetanus vaccinations; 3 polio vaccinations; and one measles, mumps, rubella vaccination) was the standard.
Childhood immunization rates were low when assessed using strict adherence to vaccination recommendations. At age 18 months, 28.3% were classified as UTD, and 6.3% were classified as AAI. Compared to children not up-to-date, UTD children were more likely to have public rather than private providers, to have had older mothers, and less likely to have been African-American. Among UTD children, AAI children were more likely to reside in urban areas.
Low-income children continue to be under-immunized, even under a managed care initiative. Health care providers and child health advocates need to continue pressure for programs that will increase adherence to nationally recommended guidelines.
Medicaid; managed care; immunization; children
A study was conducted to evaluate the immunization status of migrant farm worker children in South Carolina. Results of this study indicate that the children receive their immunizations at times which are significantly later than the recommended schedule. The first, second, third, and fourth oral poliomyelitis vaccine (OPV) doses are being given approximately 10, 15, 23, and 32 months late, respectively. Diphtheria, pertussis, tetanus vaccine (DPT) is likewise late with the first, second, third, and fourth doses occurring 9, 14, 20, and 26 months late. The fifth booster dose in both series was timed properly. The mumps, measles, rubella vaccine (MMR) is approximately 28 months late, on average. An evaluation of antibody status of 41 migrant farm worker children (5-10 years old) revealed that, even with aberrant patterns of administration, all children had adequate antibody titers. These data indicate that, although adequate levels of protection are reached with the pattern of immunization that migrant farm worker children have, there are large groups of children that are unprotected early in life when they are most susceptible to these diseases.
This study compares the presence of environmental poliovirus in two Argentinean populations using oral poliovirus vaccine (OPV) or inactivated poliovirus vaccine (IPV). From January 2003 to December 2005, Córdoba City used IPV in routine infant immunizations, with the exception of intermittent OPV use in August 2005. Between May 2005 and April 2006, we collected weekly wastewater samples in Córdoba City and the province's three major towns, which continued OPV use at all times. Wastewater samples were processed and analyzed for the presence of poliovirus according to WHO guidelines. During the months of IPV use in Córdoba City, the overall proportion of poliovirus-positive samples was 19%. During an intermittent switch from IPV to OPV, this proportion increased to 100% within 2 months. During the 3 months when IPV was reintroduced to replace OPV, a substantial proportion of samples (25%) remained positive for poliovirus. In the OPV-using sites, on average, 54% of samples were poliovirus positive. Seventy-seven percent of poliovirus isolates showed at least one mutation in the VP1-encoding sequence; the maximum genetic divergence from the Sabin strain was 0.7%. Several isolates showed mutations on attenuation markers in the VP1-encoding sequence. The frequency or type of virus mutation did not differ between periods of IPV and OPV use or by virus serotypes. This study indicates that the sustained transmission of OPV viruses was limited during IPV use in a middle-income country with a temperate climate. The continued importation of poliovirus and genetic instability of vaccine strains even in the absence of sustained circulation suggest that high poliovirus vaccine coverage has to be maintained for all countries until the risk of reintroduction of either wild or vaccine-derived poliovirus is close to zero worldwide.
The WHO aims for 90% coverage of the Expanded Program on Immunization (EPI), which in Guinea-Bissau included BCG vaccine at birth, three doses of diphtheria−tetanus−pertussis vaccine (DTP) and oral polio vaccine (OPV) at 6, 10 and 14 weeks and measles vaccine (MV) at 9 months when this study was conducted. The WHO assesses coverage by 12 months of age. The sequence of vaccines may have an effect on child mortality, but is not considered in official statistics or assessments of programme performance. We assessed vaccination coverage and frequency of out-of-sequence vaccinations by 12 and 24 months of age.
Observational cohort study.
Setting and participants
The Bandim Health Project's (BHP) rural Health and Demographic Surveillance site covers 258 randomly selected villages in all regions of Guinea-Bissau. Villages are visited biannually and vaccination cards inspected to ascertain vaccination status. Between 2003 and 2009 vaccination status by 12 months of age was assessed for 5806 children aged 12–23 months; vaccination status by 24 months of age was assessed for 3792 children aged 24–35 months.
Coverage of EPI vaccinations and frequency of out-of-sequence vaccinations.
Half of 12-month-old children and 65% of 24-month-old children had completed all EPI vaccinations. Many children received vaccines out of sequence: by 12 months of age 54% of BCG-vaccinated children had received DTP with or before BCG and 28% of measles-vaccinated children had received DTP with or after MV. By 24 months of age the proportion of out-of-sequence vaccinations was 58% and 35%, respectively, for BCG and MV.
In rural Guinea-Bissau vaccination coverage by 12 months of age was low, but continued to increase beyond 12 months of age. More than half of all children received vaccinations out of sequence. This highlights the need to improve vaccination services.
The policy to provide oral polio vaccine (OPV) at birth was introduced in low-income countries to increase coverage. The effect of OPV at birth on overall child mortality was never studied. During a trial of vitamin A supplementation (VAS) at birth in Guinea-Bissau, OPV was not available during several periods. We took advantage of this “natural experiment” to test the effect on mortality of receiving OPV at birth.
Between 2002 and 2004, the VAS trial randomised normal-birth-weight infants to 50,000 IU VAS or placebo administered with BCG. Provision of OPV at birth was not part of the trial, but we noted whether the infants received OPV or not. OPV was missing during several periods in 2004. We used Cox proportional hazards models to compute mortality rate ratios (MRR) of children who had received or not received OPV at birth.
A total of 962 (22.1%) of the 4345 enrolled children did not receive OPV at birth; 179 children died within the first year of life. Missing OPV at birth was associated with a tendency for decreased mortality (adjusted MRR = 0.69 (95% CI = 0.46–1.03)), the effect being similar among recipients of VAS and placebo. There was a highly significant interaction between OPV at birth and sex (p = 0.006). Not receiving OPV at birth was associated with a weak tendency for increased mortality in girls (1.14 (0.70–1.89)) but significantly decreased mortality in boys (0.35 (0.18–0.71)).
In our study OPV at birth had a sex-differential effect on mortality. Poliovirus is almost eradicated and OPV at birth contributes little to herd immunity. A randomised study of the effect of OPV at birth on overall mortality in both sexes is warranted.
In Pakistan, a high proportion of children fail to complete third dose of diphtheria-tetanus-pertussis (DTP3) after having received the first dose (DTP1). A cohort study was conducted to identify the factors predicting three doses of diphtheria–tetanus–pertussis (DTP3) completion among children who have received DTP1 at six centres of Expanded Programme on Immunization (EPI) in rural Pakistan.
We analyzed a cohort of mother–child pairs enrolled at DTP1 between November 2005 and May 2006 in the standard care group of a larger randomized controlled trial. Data were collected from mothers on a structured questionnaire at enrolment, and each child was followed up at clinic visits for 90 days to record dates of DTP2 and DTP3. Multivariable log-binomial regression analysis was performed to identify the independent predictors of DTP3 completion.
Only 39% (149/378) of enrolled children completed DTP3 during the follow-up period. After adjusting for the centre of enrolment in multivariable analysis, DTP3 completion was higher among children who were ≤60 days old at enrolment [adjusted risk ratio (Adj. RR) 1.39, 95% confidence interval (CI): 1.06–1.82], who were living in a household with monthly household income >Rs. 3000 (US$ 50) (Adj. RR 1.76, 95% CI: 1.16–2.65), and who were living ≤10 min away from EPI centre (Adj. RR 1.31, 95% CI: 1.04–1.66).
Interventions targeting childhood immunization dropouts should focus on bringing more children to EPI centres on-time for initial immunization. Relocation of existing EPI centres and creation of new EPI centres at appropriate locations may decrease the travel time to the EPI centres and result in fewer immunization dropouts.
childhood immunization; Expanded Programme on Immunization; dropouts; determinants; cohort study; Pakistan
This report describes a case of acute flaccid paralysis after administration of oral polio vaccine (OPV). A 4 month-old male patient with the decreased movement of left lower extremity for 1 month was transferred to the Department of Pediatrics. He received OPV with DTaP at 2 months of age. Flaccid paralysis was detected 4 weeks after OPV immunization. Attempts to isolate Sabin-like viruses in the two stool and CSF samples failed because those specimens were collected more than 2 month after the onset of paralysis. Hypotonic monoparesis (GIV/V), hypotonia and atrophy on the left lower extremity, and ipsilateral claw foot persisted for more than 18 months, while we followed him with rehabilitation therapy. This is the first case of officially approved, recipient vaccine-associated paralytic poliomyelitis in Korea.
Poliovirus vaccine; Poliomyelitis
The introduction of pneumococcal conjugate vaccine (PCV) to the U.S. recommended childhood immunization schedule in the year 2000 added three injections to the number of vaccinations a child is expected to receive during the first year of life. Surveys have suggested that the addition of PCV has led some immunization providers to move other routine childhood vaccinations to later ages, which could increase the possibility of missing these vaccines. The purpose of this study was to evaluate whether introduction of PCV affected immunization coverage for recommended childhood vaccinations among 13-month olds in four large provider groups.
In this retrospective cohort study, we analyzed computerized data on vaccinations for 33,319 children in four large provider groups before and after the introduction of PCV. The primary outcome was whether the child was up to date for all non-PCV recommended vaccinations at 13 months of age. Logistic regression was used to evaluate the association between PCV introduction and the primary outcome. The secondary outcome was the number of days spent underimmunized by 13 months. The association between PCV introduction and the secondary outcome was evaluated using a two-part modelling approach using logistic and negative binomial regression.
Overall, 93% of children were up-to-date at 13 months, and 70% received all non-PCV vaccinations without any delay. Among the entire study population, immunization coverage was maintained or slightly increased from the pre-PCV to post-PCV periods. After multivariate adjustment, children born after PCV entered routine use were less likely to be up-to-date at 13 months in one provider group (Group C: OR = 0.5; 95% CI: 0.3 – 0.8) and were less likely to have received all vaccine doses without any delay in two Groups (Group B: OR = 0.4, 95% CI: 0.3 – 0.6; Group C: OR = 0.5, 95% CI: 0.4 – 0.7). This represented 3% fewer children in Group C who were up-to-date and 14% (Group C) to 16% (Group B) fewer children who spent no time underimmunized at 13 months after PCV entered routine use compared to the pre-PCV baseline. Some disruptions in immunization delivery were also observed concurrent with temporary recommendations to suspend the birth dose of hepatitis B vaccine, preceding the introduction of PCV.
These findings suggest that the introduction of PCV did not harm overall immunization coverage rates in populations with good access to primary care. However, we did observe some disruptions in the timely delivery of other vaccines coincident with the introduction of PCV and the suspension of the birth dose of hepatitis B vaccine. This study highlights the need for continued vigilance in coming years as the U.S. introduces new childhood vaccines and policies that may change the timing of existing vaccines.
This study was aimed to determine the status and related factors of age-appropriate immunization among urban-rural children aged 24-35 months in a 2005 population-based survey in Nonsan, Korea.
Materials and Methods
We conducted household survey and provider check using questionnaire and checklist to obtain data on immunization status for children, aged 24-35 months. Age-appropriate immunization was defined as status of receiving the fourth diphtheria-tetanus-pertussis (4 DTP), 3 Polio, the first measles-mumps-rubella (1 MMR) doses, and the 4 : 3 : 1 series.
Age-appropriate immunization rates were 51.7% for 4 DPT, 88.0% for 3 Polio, 87.9% for 1 MMR, and 50.3% for the 4 : 3 : 1 series. First-born children, lower perceived barrier scores, and higher perception of immunization data were significantly related to age-appropriate immunization.
The findings indicated that age-appropriate immunization rate could be improved by implementing reminder/recall service and providing the knowledge about immunization. Identification and consideration related factors would improve immunization rate and age-appropriate immunization.
Related factors; age-appropriate immunization; DPT; Polio; MMR
We studied the interactions of hepatitis B vaccine with other vaccines used in the World Health Organization expanded programs of immunization. Three groups of Senegalese children were vaccinated with hepatitis B vaccine (HB) alone, diphtheria-tetanus-pertussis (DTP)-polio vaccine alone, or a combination of hepatitis B vaccine and DTP-polio vaccines simultaneously. The immune responses to HBsAg, tetanus toxoid, diphtheria toxoid, and pertussis were measured after one and two vaccinations at 6-month intervals. The immune responses to the combination of HB vaccine and DTP-polio vaccines were similar to the immune responses observed after administration of each vaccine alone. In addition, no adverse reactions were noted. These experimental trials also demonstrated that with a DTP-polio vaccine containing 30Lf of tetanus and diphtheria toxoids, two doses given at 6-month intervals are sufficient to provide a satisfactory immune response. In the case of pertussis and HB vaccines; however, a third dose is necessary.
Since 1988, Brazil's Unified Health System has sought to provide universal and equal access to immunisations. Inequalities in immunisation may be examined by contrasting vaccination coverage among children in the highest versus the lowest socioeconomic strata. The authors examined coverage with routine infant immunisations from a survey of Brazilian children according to socioeconomic stratum of residence census tract.
The authors conducted a household cluster survey in census tracts systematically selected from five socioeconomic strata, according to average household income and head of household education, in 26 Brazilian capitals and the federal district. The authors calculated coverage with recommended vaccinations among children until 18 months of age, according to socioeconomic quintile of residence census tract, and examined factors associated with incomplete vaccination.
Among 17 295 children with immunisation cards, 14 538 (82.6%) had received all recommended vaccinations by 18 months of age. Among children residing in census tracts in the highest socioeconomic stratum, 77.2% were completely immunised by 18 months of age versus 81.2%–86.2% of children residing in the four census tract quintiles with lower socioeconomic indicators (p<0.01). Census tracts in the highest socioeconomic quintile had significantly lower coverage for bacille Calmette-Guérin, oral polio and hepatitis B vaccines than those with lower socioeconomic indicators. In multivariable analysis, higher birth order and residing in the highest socioeconomic quintile were associated with incomplete vaccination. After adjusting for interaction between socioeconomic strata of residence census tract and household wealth index, only birth order remained significant.
Evidence from Brazilian capitals shows success in achieving high immunisation coverage among poorer children. Strategies are needed to reach children in wealthier areas.
Epidemiology; ethnicity; health status; health policy; surveillance
The success of the Global Polio Eradication Initiative was remarkable, but four countries - Afghanistan, Pakistan, India and Nigeria - never interrupted polio transmission. Pakistan reportedly achieved all milestones except interrupting virus transmission. The aim of the study was to establish valid and reliable estimate for: routine oral polio vaccine (OPV) coverage, logistics management and the quality of monitoring systems in health facilities, NIDs OPV coverage, the quality of NIDs service delivery in static centers and mobile teams, and to ultimately provide scientific evidence for tailoring future interventions.
A cross-sectional study using lot quality assessment sampling was conducted in the District Nankana Sahib of Pakistan's Punjab province. Twenty primary health centers and their catchment areas were selected randomly as 'lots'. The study involved the evaluation of 1080 children aged 12-23 months for routine OPV coverage, 20 health centers for logistics management and quality of monitoring systems, 420 households for NIDs OPV coverage, 20 static centers and 20 mobile teams for quality of NIDs service delivery. Study instruments were designed according to WHO guidelines.
Five out of twenty lots were rejected for unacceptably low routine immunization coverage. The validity of coverage was questionable to extent that all lots were rejected. Among the 54.1% who were able to present immunization cards, only 74.0% had valid immunization. Routine coverage was significantly associated with card availability and socioeconomic factors. The main reasons for routine immunization failure were absence of a vaccinator and unawareness of need for immunization. Health workers (96.9%) were a major source of information. All of the 20 lots were rejected for poor compliance in logistics management and quality of monitoring systems. Mean compliance score and compliance percentage for logistics management were 5.4 ± 2.0 (scale 0-9) and 59.4% while those for quality of monitoring systems were 3.3 ± 1.2 (scale 0-6) and 54.2%. The 15 out of 20 lots were rejected for unacceptably low NIDs coverage by finger-mark. All of the 20 lots were rejected for poor NIDs service delivery (mean compliance score = 11.7 ± 2.1 [scale 0-16]; compliance percentage = 72.8%).
Low coverage, both routine and during NIDs, and poor quality of logistics management, monitoring systems and NIDs service delivery were highlighted as major constraints in polio eradication and these should be considered in prioritizing future strategies.
The study was undertaken, first, to determine the coverage rate of hepatitis B (HB) vaccine and second to evaluate the immune response to HB vaccine among children under 10 years old by measuring the level of circulating anti-HB surface antigen (anti-HBs) antibodies after immunisation with three doses.
First, 840 children were randomly selected from 4 randomly selected sites in Sana’a city to study the coverage rate of the vaccine; of these, 504 children vaccinated against HBV prior to the study, were tested (56% males and 44% females). Sera were tested for anti-HBs antibodies by ELISA quantitative technique. Each individual’s data was collected in a pre-designed questionnaire including: vaccination date, sex, and age at the time of the study.
The coverage rate of HBV vaccine was only 69.9%, being slightly higher among male children (72.1%) than female children (66.8%). A total of 276 (54.8%) of the 504 children responded to the vaccine with anti-HBs antibody level ≥ 10 mIU/ml, while 228 (45.2%) of the 504 children had non-protective anti-HBs antibodies levels (<10IU/ml). Children of ages 3–5 years had the highest protective rate (63.6%), and the lowest protective rate was in the 9–10 years age group.
This study revealed a low coverage rate of HBV vaccine and a low protective rate against HBV infection. A considerable proportion of vaccinated children should be considered for either revaccination or booster doses. There is also the need to complete HBV vaccine coverage among the child population in San’a, Yemen.
Hepatitis B; Vaccine; Children; Yemen; Sana’a
Kenya introduced a pentavalent vaccine including the DTP, Haemophilus influenzae type b and hepatitis b virus antigens in Nov 2001 and strengthened immunization services. We estimated immunization coverage before and after introduction, timeliness of vaccination and risk factors for failure to immunize in Kilifi district, Kenya.
In Nov 2002 we performed WHO cluster-sample surveys of >200 children scheduled for vaccination before or after introduction of pentavalent vaccine. In Mar 2004 we conducted a simple random sample (SRS) survey of 204 children aged 9–23 months. Coverage was estimated by inverse Kaplan-Meier survival analysis of vaccine-card and mothers' recall data and corroborated by reviewing administrative records from national and provincial vaccine stores. The contribution to timely immunization of distance from clinic, seasonal rainfall, mother's age, and family size was estimated by a proportional hazards model.
Immunization coverage for three DTP and pentavalent doses was 100% before and 91% after pentavalent vaccine introduction, respectively. By SRS survey, coverage was 88% for three pentavalent doses. The median age at first, second and third vaccine dose was 8, 13 and 18 weeks. Vials dispatched to Kilifi District during 2001–2003 would provide three immunizations for 92% of the birth cohort. Immunization rate ratios were reduced with every kilometre of distance from home to vaccine clinic (HR 0.95, CI 0.91–1.00), rainy seasons (HR 0.73, 95% CI 0.61–0.89) and family size, increasing progressively up to 4 children (HR 0.55, 95% CI 0.41–0.73).
Vaccine coverage was high before and after introduction of pentavalent vaccine, but most doses were given late. Coverage is limited by seasonal factors and family size.
We conducted a vaccine coverage survey in Kilifi District, Kenya in order to identify predictors of childhood immunization. We calculated travel time to vaccine clinics and examined its relationship to immunization coverage and timeliness among the 2169 enrolled children (median age: 12.5 months). 86% had vaccine cards available, >95% had received three doses of DTP-HepB-Hib and polio vaccines and 88% of measles. Travel time did not affect vaccination coverage or timeliness. The Kenyan EPI reaches nearly all children in Kilifi and delays in vaccination are few, suggesting that vaccines will have maximal impact on child morbidity and mortality.
Immunization coverage; Health inequities; Spatial analysis
BACKGROUND: Immunization remains the primary strategy in both the control and prevention of common childhood diseases, particularly in the developing world. Immunization and preprimary health care services were commenced in a rural community in Nigeria in 1998, when vaccine coverage for all Expanded Program on Immunization (EPI) diseases (tuberculosis, polio, diphtheria, pertussis, tetanus, measles, and hepatitis B) was considerably low with only 43% of children fully immunized. METHODS: Children aged 0-2 years and living in a rural community were recruited into the study. Data on vaccination history was collected by both vaccination card and maternal history. Three hundred and twenty-seven children were recruited into the study. Study participants were vaccinated for EPI diseases. Hepatitis-B vaccine was administered at birth, and a combined diphtheria and tetanus toxoids, and pertussis whole cell vaccine (DTP) plus hepatitis-B vaccine was administered in a single injection after six weeks. RESULTS AND CONCLUSIONS: Two years after the program was started, immunization coverage rates were 94% for BCG, 88% for DTP (third dose), and 82% for measles. All antigens showed significant improvements from baseline values (p < 0.0001). Eighty four percent of children were fully immunized against all six diseases, compared with 43% at the commencement (p < 0.0001). Hepatitis-B coverage (three doses) was 58%. The vaccination program has significantly improved vaccination coverage and could be a model for under served, non-industrialized communities.
The global eradication of poliomyelitis will require substantial changes in immunization practices. One of the proposed scenarios includes cessation of vaccination with live oral poliovirus vaccine (OPV) and the creation of an OPV stockpile for emergency response in case of the reintroduction of poliovirus into circulation. We describe here a retrospective analysis of the cessation of OPV usage in a region of the Byelorussian Republic of the former Soviet Union in 1963 to 1966. During this period, a widespread circulation and evolution of independent lineages of vaccine-derived polioviruses took place in the region. Some of these lineages appeared to originate from OPV given to 40 children in the community during this period of essentially no vaccinations. The data demonstrate very high risks associated with both the local cessation of OPV vaccination and the proposed use of OPV to control a possible reemergence of poliovirus in the postvaccination period. The high transmissibility of OPV-derived viruses in nonimmune population, documented here, and the known existence of long-term OPV excretors should be also considered in assessing risks of the synchronized global cessation of OPV usage.