Immunogenicity and immunologic memory of meningococcal C conjugate vaccine in premature infants

Vaccinations in Infants Born Preterm: An Update

Infants born prematurely (before completion of 37 weeks of gestation) are at increased risk of morbidity and mortality due to vaccine preventable diseases, mostly because of their immunological immaturity and failure of transfer of maternal protective antibodies. Despite their great need of being vaccinated, concerns on vaccine safety and efficacy, constitute the main reasons for which vaccinations are often delayed in this group. In this review we summarize the latest evidence on vaccine safety, efficacy and immunogenicity in preterm infants which is similar to full-term infants. Therefore there is no reason for delaying vaccination in this population.

Antibody persistence following meningococcal C conjugate vaccination in children and adolescents infected with human immunodeficiency virus

OBJECTIVE

HIV-infected individuals (HIVI) are threatened by meningococcal infection and presented lower response to vaccines. Data are scarce on long-term persistence of human serum bactericidal antibody (hSBA) after a meningococcal C conjugate (MCC) vaccine in HIVI youth; the authors aimed to describe this persistence in HIVI.

METHODS

HIVI and HIV uninfected individuals (HIVU), aged 2-18 years, CD4 >15% were recruited. Seroprotection (hSBA ≥1:4) at baseline and at 12-18 months after immunization was evaluated and the association of the different factors with the long-term persistence was calculated using logistic regression.

RESULTS

A total of 145 HIVI, 50 HIVU were recruited and immunized, and their median age was 11 years (median age in HIVI group was 12 years, and 10 years in HIVU group, p-value=0.02). 85 HIVI (44%) had undetectable viral load (UVL). Seroprotection rate was 27.2%: 24.1% in HIVI and 36% in HIVU 12-18 months after immunization (p=0.14). Baseline immunity (odds ratio [OR]=70.70, 95% CI: 65.2-766.6); UVL at entry (OR: 2.87, 95% CI: 0.96-8.62) and lower family income (OR: 0.09, 95% CI: 0.01-0.69) were associated with seroprotection among HIVI.

CONCLUSION

Seroprotection at 12-18 months after single dose of MCC was low for both groups, and higher among individuals who presented baseline immunity. Among HIVI, vaccine should be administered after UVL is achieved.

Safety and Immunogenicity of Pneumococcal Conjugate Vaccine in Preterm Infants: A Meta-Analysis

OBJECTIVE

To assess the safety and immunogenicity of pneumococcal conjugate vaccine (PCVs) in preterm infants.

METHODS

In accordance with the PRISM (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement (as of May 2015), a meta-analysis was conducted to evaluate the safety and immunogenicity of PCVs in preterm infants.

RESULTS

Ten thousand nine hundred sixty full-term infants and 2131 preterm infants with 344 preterm infants of <2500 g birth weight [low-birth weight (LBW)] were included, and all the subjects were immunized with either PCV-7, PCV-10 or PCV-13 in this random-effects meta-analysis. For safety, the range of risk ratio (RRs) for local reaction was from 0.88 to 1.02 and from 0.94 to 1.24 for systematic reaction respectively. For immunogenicity, either post-primary or booster vaccination with PCV-7, PCV-10 or PCV-13, genomic mean concentration (GMC) of serotypes 4, 6B, 9 V, 19F and 23F was always less in preterm infants than in full-term infants, in which huge comparison of GMC was found in serotype 19F(SMD = -0.393, 95%CI:-0.612 ~ 0.175). After primary vaccination, the combined risk ratio (RRs) of immune response against seven common serotypes and additional serotype 1 was approximated to 1.00 with narrow 95 % confidence interval (CI) between preterm infants and full-term infants, and at least 91 % sero-conversion of two additional serotypes, 5 and 7F in two cohorts was observed. Furthermore, between very-low-birth-weight (VLBW) infants of <1500 g and 1501 ~ 2500 g, overall RRs of immune response to PCV-7 administration was 0.98 (95%CI: 0.96 ~ 1.00).

CONCLUSIONS

Preterm infants have a great tolerance to PCV-7, PCV-10 or PCV-13 vaccination. PCV-7 could elicit optimal immune response post vaccination in preterm infants, even in VLBW infants.

Immunization of preterm infants

Vaccinations of premature infants are often delayed despite being at an increased risk of contracting vaccine preventable diseases. This article reviews the current knowledge on the immune response to widely used vaccines, on the protection derived from routine immunization and on vaccine safety and tolerability in a population of preterm infants. Available data evaluating the immune response of preterm infants support early immunization without correction for gestational age. For a number of antigens, the antibody response to initial doses of vaccines may be lower than that of term infants, but protective concentrations are often achieved and memory successfully induced. Vaccines are immunogenic, safe and well tolerated in preterm infants. Preterm infants should be vaccinated using the same schedules as those usually recommended for full-term infants, with the exception of the hepatitis B vaccine, where additional doses should be administered in infants receiving the first dose during the first days of life if they weighed less than 2000 g because of a documented reduced immune response.

Update on the use of meningococcal serogroup C CRM₁₉₇-conjugate vaccine (Meningitec) against meningitis

Meningitec is a CRM197-conjugated meningococcal serogroup C (MenC) vaccine, first licensed in 1999. It has been used as a primary and booster vaccine in infants, toddlers, older children and adults, and has been shown to be immunogenic and well-tolerated in all age groups, including premature infants. Vaccine effectiveness has been demonstrated using combined data on all three licensed MenC conjugate vaccines. Evidence from clinical trials, however, suggests that the different MenC conjugate vaccines behave differently with respect to the induction and persistence of bactericidal antibody and generation of immune memory. It appears that Meningitec has a less favorable immunologic profile compared particularly to tetanus toxoid (TT) MenC conjugate vaccines. Data from comparative trials have raised interesting questions on priming of the immune system by conjugate vaccines, particularly in infants. The results from these and other studies are reviewed here with specific focus on Meningitec.

13-valent pneumococcal conjugate vaccine (PCV13) in preterm versus term infants

OBJECTIVES

This study evaluated the immune response and safety profile of 13-valent pneumococcal conjugate vaccine (PCV13) in preterm infants compared with term infants.

METHODS

This Phase IV, open-label, 2-arm, multicenter, parallel-group study enrolled 200 healthy infants (preterm, n = 100; term, n = 100) aged 42 to 98 days. All subjects received PCV13 at ages 2, 3, 4 (infant series), and 12 (toddler dose [TD]) months, together with routine vaccines (diphtheria-tetanus-acellular pertussis, hepatitis B, inactivated poliovirus, and Haemophilus influenzae type b vaccine and meningococcal group C conjugate vaccine).

RESULTS

Most subjects achieved an anticapsular immunoglobulin G (IgG) antibody concentration ≥ 0.35 μg/mL for all serotypes: >85% after the infant series (except preterm infants for serotypes 5, 6A, and 6B) and >97% after TD (except for serotype 3). Preterm infants had overall lower IgG geometric mean concentrations compared with term infants; however, geometric mean fold increases after TD were similar for all serotypes. Opsonophagocytic activity results were consistent with IgG results and titers increased after TD in both groups for all serotypes, including serotype 3. PCV13 was generally well tolerated, with similar safety profiles in all preterm subgroups.

CONCLUSIONS

Immune responses were lower in preterm infants than in term infants. However, the majority of subjects in both groups achieved both pneumococcal serotype-specific IgG antibody levels after the infant series that exceeded the World Health Organization-established threshold of protection and functional antibody responses. Responses were uniformly higher after TD, reinforcing the importance of a timely booster dose. PCV13 was well tolerated regardless of gestational age.

Immunogenicity of a meningococcal serogroup C conjugate vaccine in HIV-infected children, adolescents, and young adults

Children and adolescents infected with HIV typically have a lower response to immunization than do those in the general population. In most developed countries, meningococcal serogroup C conjugate vaccine is one of the recommended vaccines for such individuals. However, there have been no studies evaluating the antibody response to this vaccine in HIV-infected children, adolescents or young adults. In this study, we evaluated that response using serum bactericidal antibody (SBA) and enzyme-linked immunosorbent assay, comparing HIV-infected with non-HIV-infected patients, as well as analysing the occurrence of side effects. In non-responders, we assessed the antibody response to revaccination. This clinical trial involved 92 patients between 10 and 20 years of age: 43 HIV-infected patients (HIV+ group) and 49 non-HIV-infected patients (HIV- group). After one dose of the vaccine, 72.1% of the HIV+ group patients and 100% of the HIV- group patients were considered protected. Of the HIV+ group patients who received a second dose of the vaccine, only 40% acquired protection. Overall, 81.4% of the HIV+ group patients acquired protection (after one or two doses of the vaccine). Side effects occurred in 16.3% and 44% of the HIV+ group and HIV- group patients, respectively. Therefore, the meningococcal serogroup C conjugate vaccine proved to be safe and effective for use in HIV-infected children, adolescents, and young adults, although their antibody response was weaker than that shown by non-HIV-infected patients. This indicates the need to discuss changes to the immunization schedule for children, adolescents, and young adults infected with HIV, in order to ensure more effective protection against meningococcal disease.

Combined Haemophilus Influenzae type B-Neisseria meningitidis serogroup C vaccine is immunogenic and well tolerated in preterm infants when coadministered with other routinely recommended vaccines

BACKGROUND

Preterm infants are at greater risk of morbidity from vaccine-preventable diseases. Therefore, their responses to vaccination are of particular interest.

METHODS

In this open, controlled, Spanish multicenter study, we assessed immunogenicity and safety following primary vaccination of 163 preterm infants (n = 56, <31 weeks' gestation; n = 107, 31-36 weeks' gestation) and 150 full-term infants (>36 weeks' gestation), with Haemophilus Influenzae type B (Hib)-MenC-TT, DTaP(diphtheria-tetanus-acellular pertussis vaccine)-HepB-IPV, and PCV7 at 2 to 4-6 months of age followed by booster vaccination at 16 to 18 months of age. Serum bactericidal activity (rabbit complement) against MenC, and antibodies to Hib and hepatitis b (anti-HBs) were determined. Local/general symptoms were assessed after each vaccination via diary cards. Serious adverse events were recorded throughout the study.

RESULTS

There were no statistically significant differences between preterm and full-term infants in either Hib or MenC seroprotection rates or geometric mean concentrations at 1 month postdose 3, before or 1 month postbooster. Postdose 3, >99% of participants had seroprotective anti-HBs antibody concentrations. Anti-HBs geometric mean concentrations was significantly lower in the <31-week group compared with other groups and this difference persisted until 16 to 18 months of age. Hib-MenC-TT vaccine was well tolerated at all ages. There was one death caused by meningococcal serogroup-B sepsis (full term). No serious adverse events were assessed by the investigator as being vaccine related.

CONCLUSIONS

Hib-MenC-TT vaccine had a similar immunogenicity and safety profile in preterm and full-term infants. These results demonstrate that preterm infants can be safely vaccinated with Hib-MenC-TT at the recommended chronologic age without impacting the responses to the Hib and MenC antigens.

Challenges in immunisation against bacterial infection in children

Polysaccharide-encapsulated organisms such as S. pneumoniae, H. influenzae type b and N. meningitidis are the leading causes of serious invasive bacterial diseases and pneumonia in children. The use of conjugate vaccines in developed countries has markedly decreased the burden of disease and mortality from these organisms through direct protection of the immunised and through herd immunity. Although conjugate vaccines are highly immunogenic, antibody levels after immunisation in early infancy wane, leading to the need for programmes which include booster doses. Understanding the generation of long-term immunity could lead to improvements in vaccine formulation and scheduling with the ultimate goal of providing more sustained protection. Prematurity is a risk factor for disease caused by polysaccharide-encapsulated bacteria and the available data indicate that preterm infants should be immunised according to their chronological age to provide early protection.

Demonstration of immunologic memory using serogroup C meningococcal glycoconjugate vaccine

BACKGROUND

Studies of glycoconjugate vaccines have traditionally used an immune challenge with a plain polysaccharide vaccine to demonstrate immunologic memory. Plain polysaccharide vaccines are poorly immunogenic in children and can induce subsequent immunologic hyporesponsiveness. We therefore assessed the use of glycoconjugate vaccines as an alternative method of demonstrating immunologic memory.

METHODS

Children immunized with hepatitis B vaccine or serogroup C meningococcal glycoconjugate vaccine (MenCC) at age 2, 3, 4 months received a plain polysaccharide meningococcal serogroup A/C vaccine (MenACP) or MenCC at age 12 months. A post hoc analysis of serum bactericidal activity responses to MenCC assessed whether this differed in MenCC primed and MenCC naive infants.

RESULTS

MenCC primed children displayed higher geometric mean serum bactericidal titers than MenCC naive children following MenACP (1518 compared with 30; P = 0.003). A similar difference was seen after a dose of MenCC to toddlers (MenCC primed: 8663, MenCC naive: 710; P < 0.001). The latter comparison became a borderline significance after adjusting for higher pretoddler immunization serum bactericidal geometric mean titers in the MenCC primed group (P = 0.068).

CONCLUSIONS

Administration of glycoconjugate vaccines provides an important alternative method of demonstrating immunologic memory, avoiding the use of plain polysaccharide vaccines that are potentially deleterious in children. This has implications for the design of all future clinical trials of glycoconjugate vaccines.

[Immunization of the preterm infant]

Premature infants have an increased risk of experiencing infectious diseases, some of which are vaccine preventable diseases. Maturation of immune responses begins with exposition to environmental antigens and in premature infants as fast as in term-infants. Premature infants must be vaccinated at 2 months of age, whatever the gestational age. Acellular Pertussis vaccine and pneumococcal conjugate vaccine must be given as early as possible, at two months of age. Immunization schedule in premature infants is the same as in full-term infants : three injections one month apart with a pentavalent vaccine : Diphteria, Tetanus, Poliomyelitis, Pertussis and Haemophilus type b. First injection of hepatitis B vaccine must not be taken in account when this vaccine is given at birth to infants under 2 kg birth weight. Premature infants 6 months of age or older and experiencing chronic lung disease have to be vaccinated against influenza. In all cases, surroundings have to be vaccinated. Apnea and/or bradycardia have been reported within the 48 hours following vaccination in premature infants before 32 weeks of gestational age and justify giving their first injection of vaccine under cardiorespiratory monitoring. These injections will be given before discharge as often as possible.

Reconsideration of the use of meningococcal polysaccharide vaccine

In 2005, a quadrivalent meningococcal conjugate vaccine was licensed in the United States for persons aged 11-55 years of age. For children aged 2-10 years with underlying diseases associated with increased risk of meningococcal disease, unconjugated meningococcal polysaccharide (MPS) vaccination is still recommended. This article reviews the increasing evidence that MPS vaccination impairs serum anticapsular antibody responses to subsequent injections of MPS or meningococcal conjugate vaccines (antibody hyporesponsiveness). Administering MPS as a probe to assess conjugate vaccine-induced immunologic memory also can extinguish subsequent memory anticapsular antibody responses, whereas conjugate vaccination regenerates memory B cells. Whether induction of antibody hyporesponsiveness or loss of immunologic memory increase the risk of acquiring meningococcal disease remains speculative. However, for children at increased risk of meningococcal disease, immunization with meningococcal quadrivalent conjugate vaccine off-label instead of MPS vaccine should be considered. Requirements for licensure of new glycoconjugate vaccines that include performing comparative clinical trials to demonstrate noninferiority with MPS vaccine, or use of a MPS challenge to assess conjugate-induced immunologic memory also should be modified because there are safer approaches for obtaining the same information.

Active immunization of premature and low birth-weight infants: a review of immunogenicity, efficacy, and tolerability

Preterm infants are at increased risk of disease and hospitalization from a number of vaccine-preventable diseases. However, these same infants have immunologic immaturities that may impact vaccine responses. Larger premature infants mount immune responses to vaccines similar to those of full-term infants, but very premature infants (<28-32 weeks' gestation at birth) may have specific defects in vaccine responsiveness. Although there are minor differences in immunogenicity, the immune responses to diphtheria, tetanus, pertussis, and polio antigens are similar enough between full-term and premature infants that clinical consequences are unlikely to result. However, the immunogenicity of Haemophilus influenzae type b conjugate vaccines varies widely among studies of premature infants, and may be affected by the choice of conjugate protein, inclusion in a combination vaccine, and by an infant's overall health. Pneumococcal conjugate vaccine is efficacious in larger premature infants, but little information is available about immunogenicity in smaller premature infants. Meningococcal group C conjugate vaccine appears immunogenic in even very premature infants, but the duration of immunity may be limited. Hepatitis B vaccine given at birth appears poorly immunogenic in infants with birth weights <1500-2000 g, with delay in the administration of the first dose yielding improved immunogenicity. Few data on influenza vaccine in premature infants are available, but infants with pulmonary disease may respond less robustly than others. Bacille Calmette Guérin vaccine appears to be most immunogenic if delayed until at least 34-35 weeks' postmenstrual age in very premature infants, although there may be non-specific advantages to its earlier administration. Premature infants may have persistently lower antibody titers than full-term infants, even years after initial immunization. Sick premature infants experience increased episodes of apnea or cardiorespiratory compromise following vaccine administration, necessitating careful monitoring. Specific factors that impair immune response, quality of the immune response, and safety and immunogenicity evaluation of new vaccines in premature infants are topics needing further research. Premature infants are at significant risk for decisions from healthcare providers that delay beginning and completing their vaccine regimens. A major challenge facing those who care for these infants is the provision of timely immunization.

Immunogenicity, safety and tolerability of meningococcal C CRM197 conjugate vaccine administered 3, 5 and 11 months post-natally to pre- and full-term infants

A total of 79 pre-term infants with a gestational age > or =32 weeks and 74 full-term infants were studied in order to evaluate the immunogenicity, safety and tolerability of meningococcal C (MenC)-CRM(197) conjugate vaccine administered 3, 5 and 11 months post-natally. The evoked immune response seemed to be substantially similar in the pre- and full-term infants, and there were only clinically marginal differences in safety and tolerability between the groups. The results support the use of two doses of MenC-CRM(197) vaccine at 3 and 5 months of age for primary immunisation, with a booster dose being given at about 1 year. In addition to reducing costs, this scheme seems to assure global immunogenicity and potential efficacy that is better than that offered by the accelerated scheme of administration with only three doses of vaccine in the first months of life, and similar to that observed with a fourth dose used as booster after the first year.

Immunisation of premature infants

Premature infants are at increased risk of vaccine preventable infections, but audits have shown that their vaccinations are often delayed. Early protection is desirable. While the evidence base for immunisation of preterm infants is limited, the available data support early immunisation without correction for gestational age. For a number of antigens the antibody response to initial doses may be lower than that of term infants, but protective concentrations are often achieved and memory successfully induced. A 2-3-4 month schedule may be preferable for immunisation of preterm infants in order to achieve protection as early as possible, but an additional dose may be required to achieve persistence of protection. This update focuses on the use of routine childhood vaccines in premature infants.