Antibody persistence in five-year-old children who received a pentavalent combination vaccine in infancy

BACKGROUND: Antibody persistence was studied in 5.5-year-old Swedish children who in infancy completed a vaccine trial of a combined diphtheria toxoid, tetanus toxoid, acellular pertussis, inactivated polio and Haemophilus influenzae type b conjugate vaccine. Three priming doses at ages 2-4-6 months induced higher geometric mean concentrations of antibodies for all antigens than did two doses at 3-5 months, but there were no differences in proportions with protective antibody concentrations. After the booster dose administered at 13 or 12 months of age, respectively, there were no differences in concentrations or proportions between the groups. METHODS: In the present follow-up serum samples from 180 of the 228 vaccinees, 88 from the 4-dose and 92 from the 3-dose group, were 4.5 years later again tested for antibodies. RESULTS: The two groups did not differ significantly in antibody concentrations or proportions with antibodies above protective or other defined levels, with the exception of poliovirus type 3 (P < or = 0.01). In all 89% had > or = 0.01 IU/ml antibodies against diphtheria by enzyme-linked immunosorbent assay and 76% by the Vero cell neutralization test, 93% had > or = 0.01 IU/ml antibodies against tetanus, 96 to 99% had detectable antibodies against the polioviruses and 97% had > or = 0.15 microg/ml H. influenzae type b antibodies. As for pertussis only 44% had detectable antibodies against pertussis toxoid by enzyme-linked immunosorbent assay but 99% by Chinese hamster ovary cell neutralization test, and 94% had detectable antibodies against filamentous hemagglutinin. CONCLUSION: We found the persistence of antibodies satisfactory, with no clinically relevant differences in antibody concentrations demonstrated between children vaccinated according to a three dose or a four dose schedule in infancy.     

Vaccination against measles at 6 months of age]

Measles immunization with the Edmonston Zagreb stain was carried out in 71 six-month-old infants. Proportions of subjects with immunity were 91% among the 47 subjects retested before one year of age and 100% among the 28 subjects retested between two and three years of age. These results support the WHO recommendation that measles immunization should be given at the age of six months. The concerns expressed by some about possible adverse effects of early measles immunization (decreased immune defenses) are discussed, as well as the transfer of maternal antibodies and persistence of these antibodies in the child. The obstacles to such studies in developing countries, including the need for repeated phlebotomies with centrifugation of specimens and freezing of sera, could be circumvented by the use of filter paper dried blood spot samples which seem to provide reliable results although with values somewhat lower than those found in frozen sera.     

Ten year follow-up of healthy children who received one or two injections of varicella vaccine

BACKGROUND: The rate of varicella and persistence of varicella antibody after a one dose vs. a two dose regimen of varicella virus vaccine live Oka/Merck (VARIVAX; Merck & Co., Inc., West Point, PA) in approximately 2000 children were compared during a 9- to 10-year follow-up period. METHODS: Children 12 months to 12 years of age with a negative history of varicella were randomized in late 1991 to early 1993 to receive either one or two injections of varicella vaccine given 3 months apart. Subjects were actively followed for varicella, any varicella-like illness or zoster and any exposures to varicella or zoster on a yearly basis for 10 years after vaccination. Persistence of varicella antibody was measured yearly for 9 years. RESULTS: Most cases of varicella reported in recipients of one or two injections of vaccine were mild. The risk of developing varicella >42 days postvaccination during the 10-year observation period was 3.3-fold lower (P < 0.001) in children who received two injections than in those who received one injection (2.2% vs. 7.3%, respectively). The estimated vaccine efficacy for the 10-year observation period was 94.4% for one injection and 98.3% for two injections (P < 0.001). Measurable serum antibody persisted for 9 years in all subjects. CONCLUSIONS: Administration of either one or two injections of varicella vaccine to healthy children results in long term protection against most varicella disease. The two dose regimen was significantly more effective than a single injection.     

Comparison of seroconversion rates between well-nourished and malnourished children after measles immunization at nine months of age

The study was based on activities developed at Embu, SP, between October 1989 and June 1990. Its purpose was to study serological turning after child vaccination against measles at the age of nine months. Two groups were compared, both within the same age limits. Group number I included eutrophic children and group number II included undernourished children. Gomes criteria was used to evaluate the childreńs nutritional state. Antibodies (AB) dosage was done through hemagglutination inhibition (HI) and ELISA. These two laboratory methods were also checked regarding its sensibility. Out of 130 children studied, 80 could be evaluated. From this total, 56 (70%) belonged to group I and 24 (30%) belonged to group II. When the ELISA method was used, a significantly higher seroconversion percentage (P < 0.05 or 5%) was found among children belonging to group II. This percentage was not detected when the HI method was used.     

Reimmunization of children immunized at 18 months of age with Haemophilus influenzae type b vaccine

We studied the response to reimmunization at 36 months of age with Haemophilus influenzae type b (Hib) polyribosylribitol phosphate (PRP) capsular polysaccharide vaccine. Children enrolled in the study had previously received PRP or PRP plus diphtheria and tetanus toxoids with pertussis vaccine at 18 months of age. A control group of children, who received a first dose at 36 months of age, was also studied. Ninety-five percent of children receiving a second dose of vaccine had a postimmunization anti-capsular antibody level of greater than or equal to 1 microgram/mL. In comparison, 70% of 36-month-old children who received their first dose of PRP had a postimmunization level greater than or equal to 1 microgram/mL (P = 0.09). The geometric mean titer at 37 months of age was 8.64 micrograms/mL in children who had received two doses of PRP vaccine, compared with 2.19 micrograms/mL in the group who received only one dose of PRP at 36 months of age (P = 0.04). We conclude that infants immunized at 17 to 19 months of age with PRP had an excellent immunologic response to reimmunization at 36 months of age.     

Immunogenicity of Oka/Merck varicella vaccine in children vaccinated at 12-14 months of age versus 15-23 months of age

OBJECTIVE: Recent reports suggest that breakthrough varicella may be more common in children when the Oka/Merck varicella vaccine is given at 12-14 months of age than when it is given at older ages. An analysis of 5 postlicensure clinical trials with this vaccine was conducted to evaluate immune response relative to the age of the vaccine recipient. METHODS: In 5 clinical trials, 3771 children, 12 through 23 months of age with no history of varicella, received an injection of varicella vaccine. Varicella-zoster virus (VZV) antibody was measured 6 weeks postvaccination by glycoprotein enzyme-linked immunosorbent assay (gpELISA), an assay that correlates with neutralizing antibody. Endpoints evaluated were the response rate (percent of subjects with VZV antibody > or =5 gpELISA units/mL, a titer shown to correlate with protection) and geometric mean titer (GMT) of VZV antibody. Each endpoint was compared across 3 age groups (12-14, 15-17, and 18-23 months of age). Response rates by initial VZV serostatus were evaluated for children vaccinated at 12-14 months of age to assess whether maternal antibody had an impact on the immune response. RESULTS: The response rates were similar among 12-14, 15-17, and 18-23 month olds (93.8, 90.8, and 93.1%, respectively); GMTs were significantly higher among the 12-14 month olds (15.1, 13.5, and 13.7 gpELISA units/mL, respectively). Among children 12-14 months of age, response rates and GMTs were similar regardless of their prevaccination VZV serostatus. CONCLUSIONS: Oka/Merck varicella vaccine is highly immunogenic when given to children 12-14 months of age. The immunogenicity profile is similar to that of children 15-17 and 18-23 months of age. The presence of low titers of VZV antibody before vaccination did not influence vaccine response in 12-14 month olds. These results support current recommendations for universal varicella vaccination beginning at 12 months of age.     

Seroconversion after measles vaccination at nine and fifteen months of age

BACKGROUND: Despite high vaccination coverage, single dose measles immunization programs have been unsuccessful in eliminating the disease. Because seroconversion rates are lower in infants vaccinated before 12 months of age, a second dose of measles vaccine is recommended at 15 months. The aim of this study was to determine the seroconversion rates in children after the first and second doses of measles vaccinations at 9 and 15 months of age. METHODS: Study population comprised 116 infants attending the Well Baby Clinic of Istanbul University, Faculty of Medicine. Serum specimens were obtained from children before and 1 month after the first measles (Rouvax, Schwarz strain 1000 TCID(50)) vaccine given at 9 months. A second dose was given to 72 children at 15 months of age as measles-mumps-rubella (Trimovax, Schwarz measles strain, 1000 TCID(50); Urabe Am 9 mumps strain, 5000 TCID(50); Wister RA 27/3 rubella strain, 1000 TCID(50)). Third blood samples were collected 20 months after the second vaccine. RESULTS: Passive antibody positivity rate was 5.2% at the age of 9 months. Seroconversion rate was 77.6% after the first dose and 81.9% after the second dose of measles vaccine. Of 15 children who were seronegative, 13 (86.7%) became seropositive after the immunization at 15 months. Eleven children (19.2%) seroconverted from positive to negative after the second vaccine. CONCLUSION: The two dose schedule seems to increase the seropositivity rate. Our findings also indicate that increasing vaccination coverage and revaccination at 6 years of age are important even with the early two dose schedule.     

8月龄内婴儿麻疹临床分析

近几年 ,8月龄内婴儿麻疹逐渐增多 ,现将我院1998年 1月至 2 0 0 0年 10月间 2 3例婴儿麻疹报告如下。1　临床资料1.1　一般资料男性 13例 ,女性 10例 ,其中～ 3月龄 5例 ,～ 6月龄 5例 ,～ 8月龄 13例。 2 3例均有发热 ,体温 38～ 38.9℃ 8例 ,39℃以上 15例 ,咳嗽 17例 ,结膜     

Successful immunization of infants at 6 months of age with high dose Edmonston-Zagreb measles vaccine. Cite Soleil/JHU Project Team

A group of 2097 Haitian infants 6 to 11 months of age were randomized to receive Schwarz or Edmonston-Zagreb strain measles vaccines containing 10- to 500-fold more vaccine viral particles than standard potency vaccines. No unusual adverse reactions were noted. Edmonston-Zagreb vaccines were more effective than equivalent doses of Schwarz vaccines as measured by the proportion of vaccinated children with measles antibody concentrations greater than or equal to 200 mIU/ml 2 months after vaccination and the persistence of antibody at 18 to 24 months of age. High titer Edmonston-Zagreb vaccine administered at 6 months of age induced antibody concentrations greater than or equal to 200 mIU/ml in 83% of infants by plaque reduction neutralization and 93% of infants by enzyme-linked immunosorbent assay with high rates of antibody persistence at 12 to 24 months of age. The World Health Organization recommends high titer Edmonston-Zagreb measles vaccines for routine use at 6 months of age in areas where measles is an important cause of mortality in young infants.     

Rhesus Rotavirus candidate vaccine. Clinical trial in children vaccinated between 2 and 5 months of age

Live attenuated oral rhesus Rotavirus candidate vaccine (strain MMU 18006 [lot RRV-1]) was evaluated for immunogenicity, safety, and clinical protection in a double-blind, placebo-controlled trial involving 200 infants aged 2 to 5 months when vaccinated. Vaccine-induced fourfold or greater rise of Rotavirus antibodies was seen in 62% of the infants. Febrile reactions of short duration on days 3 and/or 4 after vaccination occurred in 26% of the vaccine recipients. The clinical follow-up covered two Rotavirus seasons, in which serotypes 1 and 4 were prevalent. There were 16 cases of confirmed Rotavirus diarrhea in the placebo-treated group and 10 in the vaccine-treated group; from this a vaccine protection rate of 38% was derived. Clinical severity of Rotavirus diarrhea was assessed by a score; 13 cases in the placebo-treated group and 5 in the vaccine-treated group were regarded as severe or moderately severe, giving a vaccine protection rate of 67%. The rhesus Rotavirus vaccine induces partial protection against heterotypic Rotavirus disease, but the level of protection achieved with the present vaccine dose in this age group appears to be insufficient for a general Rotavirus vaccination.     

Antibody response of children to measles vaccine mixed with diphtheria-pertussis-tetanus or diphtheria-pertussis-tetanus-poliomyelitis vaccine

The feasibility of giving measles vaccine mixed with either diphtheria-pertussis-tetanus (DPT) or DPT-poliomyelitis (DPTP) vaccine was investigated to simplify the routine immunization schedule. Children 12 to 18 months of age, due for measles immunization, were given measles vaccine alone or mixed with DPT or DPTP. Their prevaccination and four-weeks postvaccination serum samples were tested for the measles virus hemagglutination-inhibition antibody titer. Although 191 children completed the study, only 160 were initially seronegative. The seroconversion rates and geometric mean antibody titers in children given measles vaccine alone, mixed with DPT, or mixed with DPTP were 98%, 96.3%, and 96.4% and 41, 53, and 53, respectively. Local and systemic reactions were no more frequent in children given the mixture of vaccines than in children given DPTP alone. In summary, injecting measles vaccine mixed with DPT or DPTP did not diminish its immunogenic potency or increase adverse reactions. We believe that freshly mixed measles and DPT or DPTP vaccines can be given together, thus avoiding two separate injections.