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BACKGROUND: Controlling vaccine-preventable diseases by achieving high childhood vaccination coverage levels is a national priority. However, there are few, if any, comprehensive evaluations of state immunization programs in the United States, and little attention has been given to the importance of vaccination clinic management style and staff motivation. OBJECTIVE: To evaluate the factors associated with the increase in childhood vaccination coverage levels from 53% in 1988 to 89% in 1994 in Georgia's public health clinics. DESIGN: A 1994 mail survey obtaining information on clinic vaccination policies and practices and management practices. SETTING: All 227 public health clinics in Georgia. PARTICIPANTS: Clinic nurses responsible for vaccination services. OUTCOME MEASURE: The 1994 clinic-specific coverage level for 21- to 23-month-old children for 4 doses of diphtheria and tetanus toxoids and pertussis vaccine, 3 doses of polio vaccine, and 1 dose of a measles-containing vaccine as determined by an independent state assessment of clinic coverage levels. RESULTS: Univariate analysis showed that higher coverage levels were significantly (P<.05) associated with smaller clinic size, higher proportions of clientele enrolled in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC), being a nonurban clinic, and numerous vaccination practices and policies. Multivariable analysis showed that only 8 of greater than 150 factors remained associated with higher coverage levels, including having no waiting time to be seen, having telephone reminder systems, conducting home visits for defaulters, and restricting WIC vouchers when a child was undervaccinated. Motivational factors related to higher coverage included clinic lead nurses receiving an incentive to raise coverage and lead nurses participating in assessments of clinic coverage levels by state immunization staff. CONCLUSIONS: No single factor is responsible for raising vaccination coverage levels. Efforts to improve coverage should include local assessment to provide feedback on performance and identify appropriate local solutions. Coordinating with WIC, conducting recall and reminder activities, motivating clinic staff, and having staff participate in decisions are important in raising vaccination levels.
OBJECTIVE: To examine induction and persistence of cell-mediated immunity (CMI) and antibody responses to Bordetella pertussis antigens in infants receiving antipertussis vaccines. DESIGN AND SETTING: A randomized, blinded study of 142 children receiving acellular pertussis vaccines combined with diphtheria-tetanus toxoids (DTaP) (DTaP manufactured by SmithKline Beecham [DTaP-SB], Rixensart, Belgium, and DTaP manufactured by Chiron Biocin [DTaP-CB], Siena, Italy), or a whole-cell pertussis vaccine (DTwP) (Connaught Laboratories Inc, Swiftwater, Pa), or a diphtheria-tetanus (DT) (Chiron Biocine) only vaccine. Three doses of each vaccine were given at 2, 4, and 6 months of age, and CMI and antibody responses were evaluated before and at 1 and 14 months after vaccination. METHODS AND MAIN OUTCOME MEASURES: Cell-mediated immunity was assessed by proliferation of peripheral blood mononuclear cells stimulated in vitro by B pertussis antigens (pertussis toxin, filamentous hemagglutinin, and pertactin). Antibody titers against pertussis toxin, filamentous hemagglutinin, and pertactin were determined by a standardized enzyme-linked immunosorbent assay. RESULTS: A CMI-positive response to at least 1 B pertussis antigen at 1 or both postvaccination assays was detected in 46%, 55%, and 83% of DTwP, DTaP-SB, and DTaP-CB vaccine recipients, respectively. Frequency of CMI response to individual antigens ranged from less than 4.9% against pertussis toxin in DTwP recipients to 52% against pertactin in DTaP-CB recipients. The postvaccination responses measured at 14 months equalled, or had increased frequency or intensity, that of the 1-month postvaccination responses. Elevated antibody titers against the 3 antigens were present in all DTaP recipients 1 month after vaccination and were higher in CMI-positive children than in CMI-negative children. They fell, however, to low, if not negligible, levels 14 months after vaccination. CONCLUSIONS: Acellular pertussis vaccines were better inducers of CMI response than the whole-cell vaccine, particularly against pertussis toxin. Once acquired, CMI persisted, in contrast with the rapid antibody decline. Thus, CMI responses could be a useful adjunct to serology in the evaluation of pertussis vaccine immunogenicity and a better correlate of long-term immunity to B pertussis than antibody titers.
Vaccination can have important indirect effects on the spread of an infectious agent by reducing the level of infectiousness of vaccinees who become infected. To estimate the effect of vaccination on infectiousness, one typically requires data on the contacts between susceptible and infected vaccinated and unvaccinated people. As an alternative, we propose a trial design that involves multiple independent and interchangeable populations. By varying the fraction of susceptible people vaccinated across populations, we obtain an estimate of the reduction infectiousness that depends only on incidence data from the vaccine and control groups of the multiple populations. One can also obtain from these data an estimate of the reduction of susceptibility to infection. We propose a vaccination strategy that is a trade-off between optimal estimation of vaccine efficacy for susceptibility and of vaccine efficacy for infectiousness. We show that the optimal choice depends on the anticipated efficacy of the vaccine as well as the basic reproduction number of the underlying infectious disease process. Smaller vaccination fractions appear desirable when vaccine efficacy is likely high and the basic reproduction number is not large. This strategy avoids the potential for too few infections to occur to estimate vaccine efficacy parameters reliably.
In 1995, varicella vaccination was introduced into the infant immunization schedule of the United States. Currently, many other countries are considering mass varicella vaccination. Mass vaccination has two dangers: it could increase the number of varicella cases in adults, where severity is greater, and increase cases of zoster. A deterministic, realistic, age-structured model (RAS) was built to study these concerns. Model parameter estimates were derived from a review of the literature and surveillance data from England and Wales. Different vaccine efficacy scenarios, vaccine coverages, and vaccination strategies were investigated. The model predicts that, although an upward shift in the age at infection occurs, the overall morbidity due to varicella is likely to decrease following mass infant vaccination. On the other hand, cases of zoster may significantly increase in the first 50 years following vaccination. The model predicts that, in a population similar to England and Wales (50 m people), varicella vaccination with 90% coverage would prevent 0.6 m inpatient days due to varicella but would generate an extra 1.1 m inpatient days due to zoster over the first 65 years. Thus, under base-case model assumptions, the gain in reduction of varicella morbidity from infant vaccination is offset in the short-term by the increases in zoster morbidity (using inpatient days as a proxy). Paradoxically, less effective vaccines or vaccine programmes can be more effective in reducing overall morbidity (varicella + zoster) by allowing the virus to circulate more, which produces a smaller shift in the age at infection and a smaller increase in zoster cases.
BACKGROUND: It is unknown whether further expansion of the Dutch childhood vaccination program with other vaccines will be accepted and whom should be targeted in educational strategies. AIM: To determine attitudes of parents towards possible future vaccinations for their children and the behavioural determinants associated with a negative attitude. DESIGN: Questionnaire study. METHODS: Parents of children aged between 3 months and 5 years of day-care centres were asked to fill out a questionnaire. Determinants of a negative attitude to comply with possible future vaccinations against example diseases such as pneumonia or influenza, hepatitis B, TBC, smallpox and SARS were assessed using polytomous logistic regression analysis. RESULTS: Of the 283 respondents, 123 (43%) reported a positive attitude towards all vaccinations, 129 (46%) reported to have a positive attitude to have their child vaccinated against some diseases and 31 (11%) had no intention to comply with any new vaccination. Determinants of a fully negative attitude were a high education of the parent (odds ratio [OR] 3.3, 95% confidence interval [95% CI]: 1.3-8.6), being a health care worker (OR 4.2, 95% CI: 1.4-12.6), absence of religion (OR 2.6, 95% CI: 1.0-6.7), perception of vaccine ineffectiveness (OR 6.9, 95% CI: 2.5-18.9) and the perception that vaccinations cause asthma or allergies (OR 82.4, 95% CI: 8.9-766.8). CONCLUSION: Modifiable determinants for a negative attitude to comply with new vaccinations are mainly based on lack of specific knowledge. These barriers to vaccinations might be overcome by improving health education in the vaccination program, especially when targeted at educated parents and health care workers.
Vaccine efficacy and mortality in successive cohorts of children who routinely received either Edmonston-Zagreb high-titre (EZ-HT) or Schwarz standard (SW-STD) measles vaccines have been examined in a rural area of Senegal. The 2 vaccines were equally protective against measles infection (vaccination efficacy: EZ-HT 94%; SW-STD 93%). Children who did not attend a scheduled session to receive measles vaccine had a higher mortality rate between 9 months and 2 years of age than did children receiving either EZ-HT (mortality ratio [MR] = 1.81, 95% confidence interval [CI] 1.06-3.08) or SW-STD measles vaccine (MR = 1.74, 95% CI 0.95-3.21). Children of either sex vaccinated with EZ-HT had lower mortality than their equivalents who had not received any measles vaccine. There was no difference in overall mortality between recipients of EZ-HT and SW-STD (MR = 0.96, 95% CI 0.70-1.30). Using a Cox regression analysis to adjust for sex, age and significant background factors (season and death of mother), mortality rates tended to be lower for male recipients of EZ-HT than for boys receiving SW-STD (MR = 0.73, 95% CI 0.50-1.11) and higher for girls receiving EZ-HT than for girls receiving SW-STD (MR = 1.30, 95% CI 0.81-2.09) (test of interaction between sex and vaccine, P = 0.067). The tendency to reduced survival benefit for girls following receipt of high-titre measles vaccines substantiated observations from randomized trials in Guinea-Bissau, Senegal and Haiti. Existing data provide little support for the notion that high-titre vaccine is deleterious but it may not have the same beneficial effects as standard-titre measles vaccine.
BACKGROUND: The recent introduction of acellular pertussis vaccines (Pa) offers the possibility of booster doses in older children and adults. This can be conveniently accomplished by combining acellular pertussis antigens with diphtheria and tetanus toxoids. However the optimal dosage for the booster injection has not yet been determined. OBJECTIVE: To compare the reactogenicity and immunogenicity of diphtheria-tetanus-acellular pertussis vaccines (DTPa) with lower antigen contents to a licensed DTPa vaccine when given at 4-7 years of age as a booster to DTPw-primed children. METHODS: Two hundred and twenty-six children primed with four doses of DTPw before 2 years of age were enrolled and allocated to three groups to receive one dose of either DTPa (Infanrix, SmithKline Beecham, Biologicals), a reduced antigen formulation of this vaccine (dtpa, SmithKline Beecham Biologicals), or an experimental low dose formulation (dtpa-exp; d and t, Michigan Biologic Products Institute). Reactogenicity was assessed using diary cards for 15 days. Immunogenicity was determined as antibody responses against the vaccine components in pre- and 1 month postvaccination sera. RESULTS: Of the 225 children who completed the study, 60.0-66.7% reported symptoms, with no significant differences in rates between groups. Local, systemic and unsolicited symptoms occurred with similar frequencies in all three groups, the vast majority (> 90%) being considered as mild or moderate. No serious adverse events related to vaccination were reported. After vaccination, all subjects displayed seroprotective concentrations against diphtheria and tetanus, and 98.7-100% had antibodies against the three pertussis component antigens. The group receiving the reduced dose of the licensed vaccine showed antibody concentrations comparable to those of the full dose group. However, the group receiving the experimental low dose formulation had statistically significantly lower antibody concentrations against both diphtheria and tetanus toxoids compared with the two other groups, as well as significantly lower anti FHA antibody concentrations. CONCLUSIONS: Reducing the antigen content of dtpa had no deleterious effect on the immunogenicity of the vaccine when given as a fifth dose at 4-7 years of age in DTPw-primed children. The reactogenicity profile of both the reduced antigen dtpa vaccines and DTPa were acceptable, the vast majority of local and systemic reactions being considered as mild to moderate, with no vaccine-related serious adverse events reported. The use of lower antigen content dtpa vaccine as a booster in children aged 4-7 is safe and immunogenic.
BACKGROUND: Whether human immunodeficiency virus type 1 (HIV-1)-positive subjects who test positive for isolated antibody to hepatitis B core antigen (anti-HBc) should be vaccinated with hepatitis B vaccine is not certain. Development of an anamnestic response after vaccination would suggest previous hepatitis B virus (HBV) infection, in which case vaccination is not necessary. METHODS: Sixty-nine HIV-1-positive subjects who tested negative for hepatitis B surface antigen (HBsAg) and antibody to HBsAg (anti-HBs) received vaccination with standard hepatitis B vaccine. Twenty-nine subjects (42%) tested positive for anti-HBc, and 40 (58%) tested negative for anti-HBc. An anamnestic response was defined as an anti-HBs titer of >or=10 IU/L within 4 weeks of the first vaccination. RESULTS: The overall anamnestic response rate was 16% and was not significantly different between subjects who tested positive for anti-HBc (24%) and those who tested negative for anti-HBc (10%) before vaccination (P=.18). Approximately 50% of subjects who tested positive for anti-HBc also tested positive for antibody to hepatitis Be antigen (anti-HBe). The anamnestic response rate was higher in subjects who tested positive for both anti-HBc and anti-HBe (43%) than in subjects who tested positive for anti-HBc but negative for anti-HBe (7%) (P=.035). After a complete series of vaccinations, HIV-1/hepatitis C virus (HCV)-coinfected subjects were less likely to achieve high anti-HBs titers than were subjects infected with HIV-1 alone. CONCLUSIONS: After hepatitis B vaccination, the anamnestic response rate in HIV-1-positive subjects who tested positive for isolated anti-HBc but negative for anti-HBe was low and was comparable to that in subjects who tested negative for anti-HBc. This finding suggests that testing for anti-HBc alone may not be a reliable assessment of protection from HBV infection. HIV-1/HCV coinfection may be associated with impaired responses to hepatitis B vaccine, and evaluation of strategies to improve immunogenicity of the vaccine in such individuals is warranted.
Inactivated influenza virus vaccine efficacy after annual revaccination has been reported to be less than that after first vaccination in boarding school children. We prospectively examined the immunogenicity and efficacy of this vaccine in healthy 30- to 60-year-old volunteers in Houston, Texas, over two epidemic seasons (1983-1985) encompassing outbreaks due to influenza A (H3N2 and H1N1) and influenza B viruses. A placebo group that had never (or not in recent years) received inactivated influenza virus vaccine, a group that received the vaccine for the first time (first vac), and a group given two or more recent vaccinations (multivac) were evaluated in a double-blind fashion each year. Vaccination induced higher frequencies of rise in serum antibody titer to vaccine components in first vac than in multivac volunteers, but mean postvaccination titers were similar. Clinical and virologic evaluations of illnesses during both epidemics and of influenza infections diagnosed serologically over the epidemic seasons revealed no overall reduction in illness from that in the placebo group for either vaccine group; modest reductions in influenza infection-related illness that were significant only for the multivac group against A/H3N2-related illness (55%; p less than 0.04); reduction in moderate-to-severe lower respiratory and/or systemic illness due to influenza for multivac (73%, p less than 0.025) but not first vac (15%, p greater than 0.10) volunteers during the A/H3N2 epidemic; reduction in influenza virus shedding in the multivac (54%, p less than 0.05) but not the first vac (16%, p greater than 0.10) group when compared with the placebo group for both years; and overall 63-81% reductions in documented infections with each influenza virus for both vaccine groups with the exception of A/H1N1 for the first vac group (24%, p greater than 0.10) and type B for the multivac group (58%, p = 0.067). Vaccine efficacy was only modest in these studies, but in contrast to the earlier report in boarding school children, efficacy appeared to be somewhat greater after repeated annual vaccination than after first administration.
The aim of this study was to compare the kinetics and the magnitude of the humoral immune response to two different influenza vaccine formulations, whole and split virus vaccines. BALB/c mice were immunized intramuscularly with one or two doses (3 weeks apart) of 7.5, 15 or 30 microg of haemagglutinin of monovalent A/Panama/2007/99 (H3N2) split or whole virus vaccine. The two vaccine formulations induced similar kinetics of the antibody-secreting cells response; however, differences in the magnitude were observed in the spleen and bone marrow. Vaccination with whole virus vaccine generally elicited a quicker and higher neutralizing antibody response, particularly after the first dose of vaccine. The two vaccine formulations gave different immunoglobulin G (IgG) subclass profiles. Split virus vaccine stimulated both IgG1 and IgG2a antibodies suggestive of mixed T-helper 1 (Th1) and Th2 response, whereas whole virus vaccine induced mainly an IgG2a antibody response, which is indicative of a dominant Th1 response. The increased immunogenicity of whole virus vaccine in a naïve population could reduce the vaccine concentration needed to provide protective immunity.
The objective of this study was to compare the immunogenicity and safety of a single-dose regimen and a two-dose regimen of a trivalent virosome influenza vaccine (Inflexal Berna V) with those of a trivalent subunit influenza vaccine (Influvac) in children and adolescents with cystic fibrosis (CF). In an open, randomized, multicenter study with parallel groups, 11 young children with CF (1 to 6 years old) and 53 older children and adolescents with CF (>6 years old) were randomly assigned to one of the following immunization regimens: virosome vaccine at 0.5 ml on study day 0 or 0.25 ml on days 0 and 28 or a standard regimen of subunit vaccine, i. e., 0.5 ml on day 0 for older children and 0.25 ml on days 0 and 28 for younger children. Safety assessments, i.e., recording of systemic and local adverse events (AEs) and vital signs, were made for a 5-day observation period after each immunization. Hemagglutination inhibition (HI) titers were determined at baseline and 4 weeks after the single-dose and the two-dose immunizations, respectively. Immunogenicity was assessed according to the criteria of the European Agency for the Evaluation of Medicinal Products (EMEA). Both vaccines induced comparable HI antibody titers. Seroconversion (> or =4-fold rise in HI antibody titers, reaching a titer of > or =1:40) was achieved in 41 to 100% of the participants. Seroprotection (HI titer, > or =1:40) and a >2.5-fold increase in geometric mean titers were achieved in 100% of the participants. Thus, all three EMEA requirements for influenza vaccine efficacy were met by all treatment groups and for both vaccines. The virosome vaccine, when administered as a single dose, seemed to induce superior immunogenicity compared with the standard pediatric two-dose regimen. Totals of 42 and 57% of vaccinees receiving virosome and subunit vaccines, respectively, reported at least one local AE (predominantly pain). Totals of 84 and 71% of subjects receiving virosome and subunit vaccines, respectively, complained in response to questions of at least one systemic AE (mainly cough, fatigue, coryza, or headache). The majority of events were mild or moderate and lasted 1 or 2 days only. No obvious relationship was found between AE reporting rate and vaccine formulation, age group, or dose regimen. The relatively high AE reporting rate seemed to be partly related to the symptomatology of the underlying CF disease. In summary, the virosome and subunit vaccines induced in both age groups and against all three influenza strains an efficient immune response and were well tolerated by the children and adolescents with CF.