Poor immune responses to influenza vaccination in infants

Effectiveness of seasonal influenza vaccine in elementary and middle schools: a 10-year follow-up investigation

BACKGROUND

Influenza spreads from schools to the rest of society. Thus, we conducted questionnaire surveys of influenza vaccination in elementary and middle schools in a district for 10 years to determine immunization rates and infection conditions among students who were potential sources of infection at home.

METHODS

The questionnaire-based survey on influenza vaccine administration, influenza infection, and influenza types contracted, as well as influenza immunization history, was conducted in 10 seasons over a period of 10 years.

RESULTS

In elementary schools, vaccination was associated with lower morbidity in most years, whereas in middle schools, morbidity increased among students who were vaccinated every year. Our study did not find consistent trends among faculty and staff. In addition, we found that morbidity was significantly higher among elementary (P < 0.001) and middle (P < 0.05) school students who had been vaccinated since infancy than among those who had not been vaccinated since infancy.

CONCLUSIONS

The results of this study suggest that vaccinating infants for influenza may increase the risk of contracting influenza later in life.

Updating the influenza virus library at Hokkaido University -It's potential for the use of pandemic vaccine strain candidates and diagnosis

Genetic reassortment of influenza A viruses through cross-species transmission contributes to the generation of pandemic influenza viruses. To provide information on the ecology of influenza viruses, we have been conducting a global surveillance of zoonotic influenza and establishing an influenza virus library. Of 4580 influenza virus strains in the library, 3891 have been isolated from over 70 different bird species. The remaining 689 strains were isolated from humans, pigs, horses, seal, whale, and the environment. Phylogenetic analyses of the HA genes of the library isolates demonstrate that the library strains are distributed to all major known clusters of the H1, H2 and H3 subtypes of HA genes that are prevalent in humans. Since past pandemic influenza viruses are most likely genetic reassortants of zoonotic and seasonal influenza viruses, a vast collection of influenza A virus strains from various hosts should be useful for vaccine preparation and diagnosis for future pandemics.

Recombinant Measles AIK-C Vaccine Strain Expressing Influenza HA Protein

Recombinant measles AIK-C vaccine expressing the hemagglutinin (HA) protein of influenza A/Sapporo/107/2013(H1N1pdm) (MVAIK/PdmHA) was constructed. Measles particle agglutination (PA) and influenza hemagglutinin inhibition (HI) antibodies were induced in cotton rats immunized with MVAIK/PdmHA. Cotton rats immunized with two doses of the HA split vaccine were used as positive controls, and higher HI antibodies were detected 3 weeks after the first dose. Following the challenge of A/California/07/2009(H1N1pdm), higher viral loads (10⁷ TCID50/g) were detected in the lung homogenates of cotton rats immunized with the empty vector (MVAIK) or control groups than those immunized with MVAIK/Pdm HA (10³ TCID50/g) or the group immunized with HA split vaccine (10⁵ TCID50/g). Histopathologically, destruction of the alveolar structure, swelling of broncho-epithelial cells, and thickening of the alveolar wall with infiltration of inflammatory cells and HA antigens were detected in lung tissues obtained from non-immunized rats and those immunized with the empty vector after the challenge, but not in those immunized with the HA spilt or MVAIK/PdmHA vaccine. Lower levels of IFN-α, IL-1β, and TNF-α mRNA, and higher levels of IFN-γ mRNA were found in the lung homogenates of the MVAIK/PdmHA group. Higher levels of IFN-γ mRNA were detected in spleen cell culture from the MVAIK/PdmHA group stimulated with UV-inactivated A/California/07/2009(H1N1pdm). In conclusion, the recombinant MVAIK vaccine expressing influenza HA protein induced protective immune responses in cotton rats.

Historical H1N1 Influenza Virus Imprinting Increases Vaccine Protection by Influencing the Activity and Sustained Production of Antibodies Elicited at Vaccination in Ferrets

Influenza virus imprinting is now understood to significantly influence the immune responses and clinical outcome of influenza virus infections that occur later in life. Due to the yearly cycling of influenza viruses, humans are imprinted with the circulating virus of their birth year and subsequently build a complex influenza virus immune history. Despite this knowledge, little is known about how the imprinting strain influences vaccine responses. To investigate the immune responses of the imprinted host to split-virion vaccination, we imprinted ferrets with a sublethal dose of the historical seasonal H1N1 strain A/USSR/90/1977. After a +60-day recovery period to build immune memory, ferrets were immunized and then challenged on Day 123. Antibody specificity and recall were investigated throughout the time course. At challenge, the imprinted vaccinated ferrets did not experience significant disease, while naïve-vaccinated ferrets had significant weight loss. Haemagglutination inhibition assays showed that imprinted ferrets had a more robust antibody response post vaccination and increased virus neutralization activity. Imprinted-vaccinated animals had increased virus-specific IgG antibodies compared to the other experimental groups, suggesting B-cell maturity and plasticity at vaccination. These results should be considered when designing the next generation of influenza vaccines.

Immunotherapeutic Challenges for Pediatric Cancers

Solid tumors contain a mixture of malignant cells and non-malignant infiltrating cells that often create a chronic inflammatory and immunosuppressive microenvironment that restricts immunotherapeutic approaches. Although childhood and adult cancers share some similarities related to microenvironmental changes, pediatric cancers are unique, and adult cancer practices may not be wholly applicable to our pediatric patients. This review highlights the differences in tumorigenesis, viral infection, and immunologic response between children and adults that need to be considered when trying to apply experiences from experimental therapies in adult cancer patients to pediatric cancers.

Inactivated whole virus particle vaccine with potent immunogenicity and limited IL-6 induction is ideal for influenza

In contrast to current ether- or detergent-disrupted "split" vaccines (SVs) for influenza, inactivated whole influenza virus particle vaccines (WPVs) retain the original virus structure and components and as such may confer similar immunity to natural infection. In a collaboration between academia and industry, the potential of WPV as a new seasonal influenza vaccine was investigated. Each of the four seasonal influenza vaccine manufacturers in Japan prepared WPVs and SVs from the same batches of purified influenza virus. Both mice and monkeys vaccinated with the WPVs exhibited superior immune responses to those vaccinated with the corresponding SVs. Vaccination with A/California/07/2009 (H1N1) WPV enabled mice to survive a lethal challenge dose of homologous virus whereas those vaccinated with SV succumbed to infection within 6 days. Furthermore, mice vaccinated with WPV induced substantial numbers of multifunctional CD8⁺ T cells, important for control of antigenically drifted influenza virus strains. In addition, cytokines and chemokines were detected at early time points in the sera of mice vaccinated with WPV but not in those animals vaccinated with SV. These results indicate that WPVs induce enhanced innate and adaptive immune responses compared to equivalent doses of SVs. Notably, WPV at one fifth of the dose of SV was able to induce potent immunity with limited production of IL-6, one of the pyrogenic cytokines. We thus propose that WPVs with balanced immunogenicity and safety may set a new global standard for seasonal influenza vaccines.

Prior vaccinations improve immunogenicity of inactivated influenza vaccine in young children aged 6 months to 3 years: A cohort study

In young children, infrequent antigen exposure, which is partly characterized by fewer vaccinations, may be a factor impairing the immunogenicity of inactivated influenza vaccine.We assessed the effects of prior vaccinations on age-specific immune responses in Japanese children aged 6 months to 3 years, using data from a cohort study with 266 children who had received 2 doses (0.25 mL/dose for < 3 years old, 0.5 mL/dose for 3 years old) in the 2006/2007 season. Serological measures, primarily seroprotection rates, between previously vaccinated and vaccine-naïve children were compared within 1-year age strata. The seroprotection rate was defined in 2 ways as the proportion of subjects who achieved an antibody titer of 1:40 or 1:160. Multivariate logistic regression was also performed to estimate the independent effect of prior vaccination on seroprotection rate.After the first dose, seroprotection rates with the threshold of 1:40 in vaccine-naïve 1-year-olds remained low (28% for AH1, 26% for AH3, 2% for B), similar to those of 0-year-olds. In contrast, seroprotection rates in previously vaccinated 1-year-olds (77% for AH1, 86% for AH3, 18% for B) were significantly higher than those in vaccine-naïve 1-year-olds. These seroprotection rates for AH1 and AH3 were comparable with those in previously vaccinated 2- and 3-year-olds. Although seroprotection rates for B remained low in every age stratum even after the second dose, seroprotection rate in previously vaccinated 1-year-olds (50%) was similar to that in 3-year-olds. After adjustment for age, baseline antibody titer and experience of acute febrile respiratory illness in the preceding season, odds ratios showed a significant independent positive effect of prior vaccination on seroprotection rate for every strain. After the seroprotection threshold was changed from 1:40 to 1:160, the results of the effects of prior vaccinations on immunogenicity were similar or became more evident, which demonstrate the robustness of our findings.Our study found that prior vaccinations improved poor immunogenicity among young children, especially in 1-year-olds.

Effectiveness of maternal influenza immunization in young infants in Japan

BACKGROUND

Infants with influenza, particularly those younger than 1 year of age, are at high risk of developing a severe case or of dying. Recently, owing to the spread of pandemic influenza A (H1N1) 2009, the Advisory Committee on Immunization Practices recommended maternal immunization to reduce the risk of influenza infection in pregnant women and infants. Such reporting is rare in Japan. The aim of this study was therefore to investigate the effect on the newborn of influenza vaccination of pregnant women in Japan.

METHODS

The study included 200 infants who were born to healthy mothers at Kobayashi Ladies Clinic during influenza season from November 2010 to April 2011. The incidence of fever and laboratory-confirmed influenza was assessed in the infants for the 6 months after their birth.

RESULTS

Of the 200 infants, four were excluded from this study due to loss to follow up. The 106 infants in the group whose mothers received the influenza vaccine (vaccinated group) before parturition were compared with the 90 infants in the group whose mothers did not receive the influenza vaccine (non-vaccinated group). Fever was noted in 36 infants (34.0%) in the vaccinated group and in 47 infants (52.2%) in the non-vaccinated group (P < 0.007), and the incidence of influenza was 0 (0%) and 5 (5.6%), respectively (P = 0.019). The incidence of fever and influenza among infants was significantly lower in the vaccinated group compared with the non-vaccinated group.

CONCLUSIONS

Maternal influenza immunization should be actively recommended in Japan to protect newborns from influenza viruses.

Intranasal Immunization of Mice to Avoid Interference of Maternal Antibody against H5N1 Infection

Maternally-derived antibodies (MDAs) can protect offspring against influenza virus infection but may also inhibit active immune responses. To overcome MDA- mediated inhibition, active immunization of offspring with an inactivated H5N1 whole-virion vaccine under the influence of MDAs was explored in mice. Female mice were vaccinated twice via the intraperitoneal (IP) or intranasal (IN) route with the vaccine prior to mating. One week after birth, the offspring were immunized twice via the IP or IN route with the same vaccine and then challenged with a lethal dose of a highly homologous virus strain. The results showed that, no matter which immunization route (IP or IN) was used for mothers, the presence of MDAs severely interfered with the active immune response of the offspring when the offspring were immunized via the IP route. Only via the IN immunization route did the offspring overcome the MDA interference. These results suggest that intranasal immunization could be a suitable inoculation route for offspring to overcome MDA interference in the defense against highly pathogenic H5N1 virus infection. This study may provide references for human and animal vaccination to overcome MDA-induced inhibition.

Intradermal vaccination for infants and children

Intradermal (ID) vaccination induces a more potent immune response and requires lower vaccine doses as compared with standard vaccination routes. To deliver ID vaccines effectively and consistently, an ID delivery device has been developed and is commercially available for adults. The clinical application of ID vaccines for infants and children is much anticipated because children receive several vaccines, on multiple occasions, during infancy and childhood. However, experience with ID vaccines is limited and present evidence is sparse and inconsistent. ID delivery devices are not currently available for infants and children, but recent studies have examined skin thickness in this population and reported that it did not differ in proportion to body size in infants, children, and adults. These results are helpful in developing new ID devices and for preparing new vaccines in infants and children.

Control of influenza infection is impaired by diminished interferon-γ secretion by CD4 T cells in the lungs of toddler mice

Respiratory viral infections, such as influenza, can lead to delayed viral clearance in toddlers, possibly exacerbating disease morbidity. We hypothesized that defective CD4 T cells in toddlers may contribute to a failure to clear virus at a similar rate to adults. Thus, we developed a young mouse model to examine potential divergent responses between toddlers and adults. We determined that young mice (toddler mice, 21 d old) were actively generating and recruiting effector/memory T cells, whereas memory populations were firmly established in older, adult mice (8-10 wk old). We infected toddler and adult mice with influenza A/PR8/34 (H1N1) and found young mice had elevated morbidity, as measured by enhanced weight loss and lower partial pressure of oxygen levels, throughout the infection, thus, modeling the higher morbidity observed in children (<2 y old) during infection. Early viral loads were comparable to adult mice, but toddler mice failed to clear virus by 10 d postinfection. This delayed clearance corresponded to poor lung recruitment of CD4 T cells, lower antiviral T cell responses, and lower B cell/antibodies in the lungs. Mechanistically, diminished interferon-γ was detected in the lungs of toddler mice throughout the infection and corresponded to intrinsic, rather than extrinsic, CD4 T cell limitations in interferon-γ transcription. Moreover, defects in interferon-γ production appeared downstream from signal transducer and activator of transcription 4 in the interleukin-12 signaling pathway, suggesting maturational delays different from neonates. Importantly, recombinant interferon-γ supplementation rescued CD4 T cell numbers in the lungs and influenza-specific antibody formation. This study highlights the intrinsic limitations in CD4 T cell effector functions that may arise in toddlers and contribute to disease pathology.

Immunogenicity of the trivalent inactivated influenza vaccine in young children less than 4 years of age, with a focus on age and baseline antibodies

In this study, we assessed the effects of the prevaccination titer and age on the immunogenicity of a low dose of influenza vaccine in children less than 4 years of age. A total of 259 children received two vaccine doses (0.1 ml for 0-year-olds and 0.2 ml for children 1 year of age or older) 4 weeks apart during the 2005/2006 season. The hemagglutination inhibition antibody titers were measured before vaccination and 4 weeks after the first and second doses. The geometric mean titer, mean fold rise, seroresponse proportion (≥4-fold rise in titer), and seroprotection proportion (titer ≥1:40) were calculated for the prevaccination titer and age categories. A multivariate logistic regression analysis was performed using the seroresponse and seroprotection proportions as dependent variables and the prevaccination titer and age as explanatory variables. As for the seroresponse against the H1 antigen after the first dose, the adjusted odds ratios of the prevaccination titers (versus <1:10) were 2.2 (95% confidence interval, 0.8 to 5.8) at 1:10 to 1:20 and 0.14 (0.04 to 0.49) at ≥1:40. The corresponding figures for ages were 0.03 (0.01 to 0.07) for the 0-year-olds and 0.17 (0.08 to 0.34) for the 1-year-olds compared with the 2- to 3-year-olds (Ptrend < 0.001). Similar results were also obtained for the H3 and B strains. Significantly elevated odds ratios for seroprotection were observed with greater prevaccination titers and older ages for all strains. The prevaccination titer and age were independently associated with the antibody response in young children. The immune response was weaker in the younger children and those without preexisting immunity.

Taking stock of infections and antibiotic resistance in the elderly and long-term care facilities: A survey of existing and upcoming challenges

Treating elderly patients with infections represents one of the greatest challenges to health-care providers. Older adults are the largest growing sector of the population and suffer excessively from infectious diseases such as pneumonia, urinary tract infections (UTIs), and skin and soft-tissue infections. Often because of disabilities, the elderly require treatment of infectious diseases in long-term care facilities (LTCFs). As a result of antibiotic use, LTCFs have become "reservoirs of resistance" and multi-drug resistant (MDR) pathogens are frequently recovered. Clinicians also need to be aware of the impairment of immune function and other emerging chronic infections (HIV, HCV) that are now present in the elderly. Despite vigilance regarding this issue, delays in diagnosis and initiation of therapy are common. This article reviews the changing landscape of infections in the elderly and the challenge these syndromes present in the context of an increasing older population that requires dedicated resources.

Influenza A/H1N1 MF59-adjuvanted vaccine in preterm and term children aged 6 to 23 months

OBJECTIVE

This study was designed to evaluate the immunogenicity, safety, and tolerability of a monovalent 2009 pandemic influenza A/H1N1 MF59-adjuvanted vaccine in children aged 6 to 23 months who had different gestational ages (GAs) at birth.

METHODS

The study involved 105 children: 35 preterm subjects with a GA of <32 weeks; 35 preterm subjects with a GA of 32 to 36 weeks; and 35 term subjects with a GA of 37 to 42 weeks. Each child received 2 intramuscular vaccine doses (Focetria [Novartis, Siena, Italy]): dose 1 at enrollment and dose 2 after 4 weeks (28 ± 2 days). Serum samples for antibody measurements were collected immediately before administration of dose 1, before administration of dose 2 (28 ± 2 days after baseline), and 4 weeks later (56 ± 2 days after baseline). Local and systemic reactions were assessed during the 14 days after each vaccination.

RESULTS

Of the 101 children who completed the study 32 out of 34 preterm subjects with a GA of <32 weeks, all of the preterm subjects with a GA of 32 to 36 weeks, and all of the term subjects seroconverted and were seroprotected after the first vaccine dose. Local and systemic tolerability was good in all of the groups, but fever was significantly more common after the first dose than after the second dose (P < .05), and there were no between-group differences.

CONCLUSIONS

A single dose of 2009 pandemic influenza A/H1N1 MF59-adjuvanted vaccine evoked a significant immune response against pandemic influenza A/H1N1 virus in children aged 6 to 23 months even if their GA was <32 weeks. The vaccine had a good safety and tolerability profile.

Trivalent live attenuated intranasal influenza vaccine administered during the 2003-2004 influenza type A (H3N2) outbreak provided immediate, direct, and indirect protection in children

OBJECTIVE

Live attenuated influenza vaccine may protect against wild-type influenza illness shortly after vaccine administration by innate immunity. The 2003-2004 influenza A (H3N2) outbreak arrived early, and the circulating strain was antigenically distinct from the vaccine strain. The objective of this study was to determine the effectiveness of influenza vaccines for healthy school-aged children when administered during the influenza outbreak.

DESIGN/METHODS

An open-labeled, nonrandomized, community-based influenza vaccine trial was conducted in children 5 to 18 years old. Age-eligible healthy children received trivalent live attenuated influenza vaccine. Trivalent inactivated influenza vaccine was given to children with underlying health conditions. Influenza-positive illness was compared between vaccinated and nonvaccinated children. Medically attended acute respiratory illness and pneumonia and influenza rates for Scott and White Health Plan vaccinees were compared with age-eligible Scott and White Health Plan nonparticipants in the intervention communities. Herd protection was assessed by comparing age-specific medically attended acute respiratory illness rates in Scott and White Health Plan members in the intervention and comparison communities.

RESULTS

We administered 1 dose of trivalent live attenuated influenza vaccine or trivalent inactivated influenza vaccine to 6569 and 1040 children, respectively (31.5% vaccination coverage), from October 10 to December 30, 2003. The influenza outbreak occurred from October 12 to December 20, 2003. Significant protection against influenza-positive illness (37.3%) and pneumonia and influenza events (50%) was detected in children who received trivalent live attenuated influenza vaccine but not trivalent inactivated influenza vaccine. Trivalent live attenuated influenza vaccine recipients had similar protection against influenza-positive illness within 14 days compared with >14 days (10 of 25 vs 9 of 30) after vaccination. Indirect effectiveness against medically attended acute respiratory illness was detected in children 5 to 11 and adults 35 to 44 years of age.

CONCLUSION

One dose of trivalent live attenuated influenza vaccine was efficacious in children even when administered during an influenza outbreak and when the dominant circulating influenza virus was antigenically distinct from the vaccine strain. We hypothesize that trivalent live attenuated influenza vaccine provides protection against influenza by both innate and adaptive immune mechanisms.

Vaccine effectiveness against medically attended, laboratory-confirmed influenza among children aged 6 to 59 months, 2003-2004

OBJECTIVES

Influenza is a leading cause of illness among children. Studies rarely have measured influenza vaccine effectiveness among young children, particularly when antigenic match between vaccine and circulating viruses is suboptimal. We assessed vaccine effectiveness against medically attended, laboratory-confirmed influenza for children who were aged 6 to 59 months during the 2003-2004 influenza season.

METHODS

In a case-control study that was conducted in a single pediatric practice, case patients who were aged 6 to 59 months and had laboratory-confirmed influenza were age matched 1:2 to eligible control subjects. Vaccination status was ascertained as of the date of the case patient's symptom onset. Conditional logistic regression was used to calculate vaccine effectiveness, adjusting for underlying medical conditions and health care usage.

RESULTS

We identified 290 influenza case patients who were seen for medical care from November 1, 2003, to January 31, 2004. Vaccine effectiveness among fully vaccinated children, compared with unvaccinated children, was 49%. Partially vaccinated children who were aged 6 to 23 months had no significant reduction in influenza (vaccine effectiveness: -70%), but partially vaccinated children who were aged 24 to 59 months had a significant (65%) reduction in influenza, compared with unvaccinated children.

CONCLUSIONS

Full vaccination provided measurable protection against laboratory-confirmed influenza among children who were aged 6 to 59 months during a season with suboptimal vaccine match. No vaccine effectiveness was identified with partial vaccination among children who were aged 6 to 23 months, affirming that children need to be fully vaccinated to obtain protective effects. These results strengthen the evidence of the vaccine's ability to reduce substantially the burden of disease in this age group.

Humoral and cellular immune responses in children given annual immunization with trivalent inactivated influenza vaccine

BACKGROUND

There have been no prior reports of the frequency of circulating influenza-specific, interferon gamma-producing memory CD4+ and CD8+ T-cells in healthy children who have received multiple influenza immunizations.

METHODS

We evaluated 21 previously immunized children, ages 3 to 9 years, before and 1 month after administration of trivalent inactivated influenza vaccine. Frequencies of influenza-specific CD4+ and CD8+ T-cells stimulated with trivalent inactivated influenza vaccine or A/Panama (H3N2) virus were determined by flow cytometry, and antibody responses to vaccine strains and a drifted H3N2 strain were measured by hemagglutination inhibition assay and neutralizing antibody assays.

RESULTS

Mean change in CD4+ and in CD8+ T-cell frequencies after immunization was 0.01% (P > 0.39) with postimmunization CD4+ frequencies higher than CD8+ frequencies. Children with more previous vaccinations had a higher baseline frequency of CD4+ T-cells (P = 0.0002) but a smaller increase or even a decline from baseline after immunization (P = 0.003). An association between age and change in frequency was not detected. Baseline geometric mean titers (GMTs) and seroprotection rates were significantly higher in older children against A/Panama (neutralizing baseline GMT, P = 0.0488) and A/New Caledonia (hemagglutination inhibition baseline GMT and seroprotection, P < 0.0297). Baseline GMTs against B/Hong Kong were not associated with age or quantity of prior vaccinations.

CONCLUSIONS

These findings suggest that children may plateau in CD4+ T-cell responses to influenza antigens with repeated exposures and that the number of exposures may play a large role in building a memory CD4+ T-cell response to influenza A, perhaps independently from age.

Time course characteristics of human herpesvirus 6 specific cellular immune response and natural killer cell activity in patients with exanthema subitum

The time-course of cell-mediated immunity in exanthema subitum is not well documented. The lymphoproliferative response to purified human herpesvirus 6 (HHV-6) antigen and to phytohemagglutinin was measured and natural killer (NK) cell activities determined in three consecutive specimens obtained biweekly from 18 young children and infants with exanthema subitum. Virus isolation and PCR detection of virus DNA and determination of neutralization antibody to HHV-6 and -7 were also carried out. The magnitude of the HHV-6 specific lymphoproliferative response varied; however, in most cases the time course kinetics revealed a low response in the acute phase with a subsequent gradual increase. In contrast, NK cell activities were high in the acute phase and declined gradually during convalescence. The lymphoproliferative response to phytohemagglutinin did not show a consistent trend in kinetics of time; however, dynamic changes in activity were observed in patients during the acute and convalescent periods. The results suggest that NK cells play a major role in resolving acute phase infection while specific lymphocyte activity develops later. The cause of the delayed development of HHV-6 specific lymphoproliferative response is unknown. The lymphoproliferative response to phytohemagglutinin ratios implied that HHV-6 infection has some impact on host T-cell immunity during the course of exanthema subitum.

Serum immunoglobulin levels do not affect antibody responses to influenza HA vaccine in preterm infants

Antibody responses to two doses of influenza hemagglutinin (HA) vaccine were evaluated in 45 previously unimmunized preterm infants aged 6-11 months before the 2003/2004 influenza season. Twenty-three (51.1%), 21 (46.6%) and 2 (4.4%) of the subjects acquired protective (>or=1:40) hemagglutination inhibition (HI) antibody titers after vaccination for A/New Caledonia (H1N1), A/Panama (H3N2) and B/Shandong, respectively. Antibody responses to A (H1N1), A (H3N2) appeared to be comparable to those reported on full-term infants of similar ages vaccinated with the identical vaccine. Serum IgG levels at vaccination had no positive association with antibody responses on univariate or multivariate analysis, indicating that prolonged hypogammaglobulinemia after 6 months of age in preterm infants was not a factor to affect antibody responses to influenza HA vaccine.

Maternal immunization with both hemagglutinin- and neuraminidase-expressing DNAs provides an enhanced protection against a lethal influenza virus challenge in infant and adult mice

Maternal immunization is the major form of protection against many infectious diseases in early life. In this report, transmission of vaccine-specific maternal antibodies and protection of offspring against a lethal influenza virus challenge were studied. Adult female BALB/c mice were immunized intramuscularly with plasmid DNAs encoding influenza virus hemagglutinin (HA), neuraminidase (NA), or mixture of the two plasmids. The levels of specific antibodies in sera of offspring at different ages and the survival rates following the lethal viral challenge were valued. The results showed effective transmission of maternal antibodies and long-lasting protection in offspring. Along with the growth of offspring, the antibody titers in vivo decreased and the ability against virus infection decreased accordingly. The HA-specific maternal antibodies protected the offspring from a lethal influenza infection up to 2 weeks old, and the NA-specific maternal antibodies protected offspring up to 4 weeks old. Furthermore, antibodies transferred by the mother immunized with the mixture of HA and NA DNAs protected the offspring up to 6 weeks old. This suggests that maternal immunization with a mixture of HA and NA DNAs provide the most effective protection against the virus challenge for the offspring of mice.

Immune response after influenza vaccination in children with cancer

PURPOSE

To assess the immune response to inactivated trivalent split influenza vaccine in children with cancer.

PROCEDURES

Forty-four children with various types of malignancies received two doses of influenza vaccine 2-4 weeks apart. Hemagglutinin-inhibition (HI) antibody titers were determined in paired sera obtained just before the first vaccination and 4 weeks after the second vaccination.

RESULTS

Influenza vaccine was administered to all children without any serious adverse effects. Protective titer rates (proportion of patients achieving antibody titers > or =40 among those with pre-vaccination titers <40) and response rates (proportion of patients with fourfold or more antibody rise) were 72% and 65% for H1N1, 60% and 40% for H3N2, and 38% and 46% for influenza B, respectively. However, patients on chemotherapy showed a significantly lower immune response to influenza A than those having completed chemotherapy; protection titer rates were 42% versus 90% for H1N1 (P = 0.006) and 25% versus 83% for H3N2 (P = 0.019). For influenza B, patients with low IgG showed a lower response rate than those with high IgG (29% vs. 61%, P = 0.040). Multivariate analysis revealed that factors significantly associated with a lower immune response were low IgG (P < 0.001) and administration of chemotherapy (P = 0.003) for H1N1, administration of chemotherapy (P = 0.008) for H3N2, and low white blood cell (WBC) count (P = 0.030) and low IgG (P = 0.030) for influenza B.

CONCLUSIONS

Influenza vaccination given to children with cancer was safe and induced immune reaction comparable to healthy children, although patients on chemotherapy and/or with chemotherapy-related conditions had a limited ability to produce a sufficient immune response.