Protective effect of single-dose adjuvanted pandemic influenza vaccine in children. The safety of trivalent influenza vaccine among healthy children 6 to 24 months of age. Failure of inactivated influenza A vaccine to protect healthy children aged 6-24 months. Effectiveness of the 2003-2004 influenza vaccine among children 6 months to 8 years of age, with 1 vs 2 doses. [Influence of multiplicity of immunizations of children with inactivated influenza vaccine on immune response and the effectiveness of protection]. The efficacy of a Salmonella typhi Vi conjugate vaccine in two-to-five-year-old children. A controlled trial of a formalin-inactivated hepatitis A vaccine in healthy children. Age-specific differences in duration of clinical protection after vaccination with meningococcal polysaccharide A vaccine. Influenza vaccine in healthy preschool children.
During the first wave of A/California/7/2009(H1N1) influenza, high rates of hospitalization in children under 5 years were seen in many countries. Subsequent policies for vaccinating children varied in both type of vaccine and number of doses. In Canada, children 36 months to <10 years received a single dose of 0.25 ml of the GSK adjuvanted vaccine (Arepanrix) equivalent to 1.9 microg HA. Children 6 months to 35 months received two doses as did those 36-119 months with chronic medical conditions.
                We conducted a community-based case-control vaccine effectiveness (VE) review of children under 10 years with influenza like illness who were tested for H1N1 infection at the central provincial laboratory. Laboratory-confirmed influenza was the primary outcome, and vaccination status the primary exposure to assess VE after a single 0.25-ml dose.
                If vaccination was designated to be effective after 14 days, no vaccinated child had laboratory-confirmed influenza compared to 38% of controls. The VE of 100% was statistically significant for children <10 years of age and <5 years considered separately. If vaccination was considered effective after 10 days, VE dropped to 96% overall but was statistically significant and over 90% in all age subgroups, including those under 36 months.
                A single 0.25-ml dose of the GSK adjuvanted vaccine (Arepanrix) protects children against laboratory-confirmed pandemic influenza potentially avoiding any increased reactogenicity associated with second doses. Adjuvanted vaccines offer hope for improved seasonal vaccines in the future. The objective of this study was to assess the safety of routine trivalent influenza vaccine (TIV) administration among healthy children 6 through 23 months of age, after the Advisory Committee on Immunization Practices recommendation.
                The study was a retrospective case-control study of children receiving TIV in the first 2 seasons after the Advisory Committee on Immunization Practices recommendation. We assessed outcomes in the 42 days after vaccination in a population of 13,383 children. Each case subject was matched, according to age and gender, with 3 control subjects. Hazard ratios were calculated with conditional logistic regression analysis.
                We found no statistically significantly elevated hazard ratios for the first TIV dose. An elevated risk of pharyngitis was found for children receiving a second TIV dose. No elevated risk of seizure was found.
                These results, for a population of healthy children, showed no medically significant adverse events related to TIV among children 6 to 23 months of age. The efficacy of inactivated influenza vaccine in healthy infants and children younger than 24 months has not been confirmed. The aim of the present study was to determine the prophylactic effect of inactivated influenza vaccine against influenza A in healthy children aged 6-24 months.
                Healthy infants and young children (6-24 months old) were immunized by subcutaneous injection of inactivated influenza vaccine before influenza seasons. Age matched children were randomly assigned as the control. These children were followed up from January to April in each year (2000, 2001 and 2002). The attack rates of influenza A infection was compared and statistically assessed.
                The attack rate of influenza A virus infection in the vaccine group and the control group were 14.8% (n = 27) vs 12.5% (n = 32) in 2000 (P = 0.526); 2.8% (n = 72) vs 7.2% (n = 69) in 2001 (P = 0.203); and 3.4% (n = 52) vs 8.9% (n = 56) in 2002 (P = 0.205). The attack rates of influenza A between the two groups were not significantly different.
                Inactivated influenza vaccine did not reduce the attack rate of influenza A infection in 6-24 month old children. To evaluate the effectiveness of 1 and 2 doses of the 2003-2004 influenza vaccine in preventing medically attended influenza-like illness (ILI) among children 6 to 23 months and 6 months to 8 years of age. Design and
                Outpatient and emergency department visits and immunization records were used to conduct a retrospective cohort study among children 6 months to 8 years of age. ILI and pneumonia and influenza (P&I) outcomes were defined on the basis of International Classification of Diseases, Ninth Revision, codes. Influenza vaccine effectiveness (VE) was calculated as (1 - hazard rate ratio) x 100.
                A total of 29726 children were included in the analyses; 17.3% were 6 to 23 months of age. By November 19, 2003, the start of peak influenza activity, 7.5% and 9.9% of children 6 months to 8 years were fully or partially vaccinated against influenza, respectively. For fully vaccinated children 6 to 23 months of age, VE against ILI and P&I was 25% and 49%, respectively. No statistically significant reduction in ILI or P&I rates was observed for partially vaccinated children 6 to 23 months of age (-3% and 22%, respectively). For fully vaccinated children 6 months to 8 years of age, VE against ILI and P&I was 23% and 51%, respectively. For partial vaccination, VE was significant only for P&I (23%).
                Despite a suboptimal match between the influenza vaccine and predominant circulating strains, influenza vaccination provided substantial protection for fully vaccinated children and possibly some protection for partially vaccinated children <9 years of age. These findings support vaccinating targeted children even when the vaccine match is suboptimal, and they highlight the need to vaccinate previously unvaccinated children with 2 doses for optimal protection. The formation of immunity and epidemiological effectiveness of inactivated influenza vaccines in children, regularly immunized against influenza for three years, were evaluated. The study revealed that a year after each immunization the number of children having antibodies in liters regarded as protective decreased 2-2.5 times. At the periods of epidemics morbidity rate among the vaccines dynamically decreased in these years 1.3, 2.0 and 2.8 times. Considering that a year after the second immunization a high immune stratum (60-78%) was retained in the group under study, we propose that annual immunization of the same children be limited by a period of three years, followed by an interval of one year. Typhoid fever is common in developing countries. The licensed typhoid vaccines confer only about 70 percent immunity, do not protect young children, and are not used for routine vaccination. A newly devised conjugate of the capsular polysaccharide of Salmonella typhi, Vi, bound to nontoxic recombinant Pseudomonas aeruginosa exotoxin A (rEPA), has enhanced immunogenicity in adults and in children 5 to 14 years old and has elicited a booster response in children 2 to 4 years old.
                In a double-blind, randomized trial, we evaluated the safety, immunogenicity, and efficacy of the Vi-rEPA vaccine in children two to five years old in 16 communes in Dong Thap Province, Vietnam. Each of the 11,091 children received two injections six weeks apart of either Vi-rEPA or a saline placebo. Cases of typhoid, diagnosed by the isolation of S. typhi from blood cultures after 3 or more days of fever (a temperature of 37.5 degrees C or higher), were identified by active surveillance over a period of 27 months. We estimated efficacy by comparing the attack rate of typhoid in the vaccine group with that in the placebo group.
                S. typhi was isolated from 4 of the 5525 children who were fully vaccinated with Vi-rEPA and from 47 of the 5566 children who received both injections of placebo (efficacy, 91.5 percent; 95 percent confidence interval, 77.1 to 96.6; P<0.001). Among the 771 children who received only one injection, there was 1 case of typhoid in the vaccine group and 8 cases in the placebo group. Cases were distributed evenly among all age groups and throughout the study period. No serious adverse reactions were observed. In all 36 children studied four weeks after the second injection of the vaccine, levels of serum IgG Vi antibodies had increased by a factor of 10 or more.
                The Vi-rEPA conjugate typhoid vaccine is safe and immunogenic and has more than 90 percent efficacy in children two to five years old. The antibody responses and the efficacy suggest that this vaccine should be at least as protective in persons who are more than five years old. Although inactivated hepatitis A vaccine is known to be well tolerated and immunogenic in healthy children and adults, its efficacy has yet to be established.
                To evaluate the efficacy of the hepatitis A vaccine in protecting against clinically apparent disease, we conducted a double-blind, placebo-controlled trial in an Hasidic Jewish community in upstate New York that has had recurrent outbreaks of hepatitis A. At the beginning of a summer outbreak, 1037 healthy seronegative children 2 to 16 years of age were randomly assigned to receive one intramuscular injection of a highly purified, formalin-inactivated hepatitis A vaccine or placebo. A case was defined by the presence of typical signs and symptoms, a diagnostic increase in IgM antibody to hepatitis A, and a serum concentration of alanine aminotransferase at least twice the upper limit of normal. Cases occurring greater than or equal to 50 days after the injection were included in the evaluation of efficacy. The children were followed for a mean of 103 days.
                A total of 519 children received vaccine, and 518 received placebo. The vaccine was well tolerated, with no serious adverse reactions. From day 50 after the injection, 25 cases of clinically apparent hepatitis A occurred in the placebo group and none in the vaccine group (P less than 0.001), confirming that the vaccine had 100 percent protective efficacy. Before day 21, seven cases occurred in the vaccine group and three cases in the placebo group. After that time, there were no cases among vaccine recipients and 34 cases among placebo recipients.
                The inactivated purified hepatitis A vaccine that we tested is well tolerated, and a single dose is highly protective against clinically apparent hepatitis A. Sequential case-control studies were used to monitor changes in the clinical protection induced by group A meningococcal polysaccharide vaccine over a 3-year period. Overall, vaccine efficacy declined from 87% 1 year after vaccination to 70% and 54% at 2 and 3 years, respectively. When stratified by age at time of vaccination the data showed that, although vaccine efficacy remained high in children greater than or equal to 4 years of age (vaccine efficacy 85%, 74%, and 67% at 1, 2, and 3 years after vaccination, respectively), it declined dramatically in those less than 4 years of age at time of vaccination (vaccine efficacy 100%, 52%, and 8%, respectively, at 1, 2, and 3 years after vaccination). Thus, a single dose of group A meningococcal vaccine does not yield lasting clinical protection in children less than 4 years of age. Studies of influenza vaccination in healthy children have not definitely answered the question of their efficacy.
                We have carried out a randomized trial in a well selected population of healthy preschool children in Sardinia, Italy. During October 1995, 344 children aged 1 to 6 years, were randomly assigned to receive influenza vaccine (n=177) or no treatment (n=167). Two doses of a trivalent subvirion vaccine, containing 15mg of highly purified surface antigens from the component strains A/Johannesburg/33/94-like, A/Singapore/6/86-like and B/ Beijing/184/ 93-like were administered. Follow-up data were collected from December 1, 1995 through April 30, 1996.
                Seroconversion was documented in 17 out of 17 children. No specific systemic symptoms or severe local reactions were observed after vaccination. Influenza-like episodes, defined by the presence of fever and cough or sore throat that lasted at least 72 hours, occurred in 63 (37.7%) of unvaccinated children and in 22 (12.4%) of vaccinated ones. The corresponding reduction in disease incidence was 67% (95% CI: 0.59-0.74). Three episodes of otitis were observed among children in the control group versus zero among vaccinated children (p=0.07). Mean duration of day care center absenteism was significantly reduced by vaccination (2.3 days in unvaccinated and 0.5 day in vaccinated children, p<0.001)
                Influenza vaccine is safe and effective in healthy preschool children. However the favourable implications of vaccination on disease rate in subsequent years have to be evaluated.
The  vaccine was strongly protective for the first year in children over five and adults, but its efficacy beyond the first year could not be determined with precision. Children aged one to five years in low-income countries were also protected but the efficacy in this age group could not be determined. While the vaccine was strongly protective among children aged three months to five years in Finland, the efficacy in narrower age strata could not be determined. The sample size was too small to draw conclusions on the effect of booster doses.