Response of preterm infants to hepatitis B vaccine

A retrospective study of hepatitis B vaccination in preterm birth and low birth weight infants born to hepatitis B surface antigen-positive mothers: Time to close the policy-practice gap

National Immunization Program-version 2016 (ISIV-NIP-v2016) recommended a 4-dose hepatitis B vaccine (HepB) schedule for preterm birth (PTB) and low birth weight (LBW) infants born to HBsAg-positive mothers. However, the implementation of this immunization strategy in the past five years has not been fully evaluated in China. We reviewed the data of pregnant women and live-born infants from 24 hospitals between 2016 and 2021 in Lu'an, Anhui province, to estimate the prevalence of PTB, LBW, and hepatitis B virus (HBV) infected pregnant women. We analyzed the vaccination status of HepB and HBIG among PTB and LBW infants born to HBsAg-positive mothers. A total of 160 222 pregnant women and 159 613 live-born infants were included in this study. The estimated prevalence of PTB, LBW and HBV-infected pregnant women was 3.86% (range: 3.28%-5.10%), 2.77% (range: 2.12%-3.66%), and 3.27% (range: 3.03%-3.49%), respectively. We screened 340 PTB and LBW infants born to HBsAg-positive mothers between 2016 and 2020. We found that the coverage of HepB and HBIG among them was 100% and 99.39%. However, the timely vaccination rate of the HepB birth dose was only 78.59% and only four children (1.22%) received the 4-dose HepB as recommended by ISIV-NIP-v2016. The 4-dose of HepB for PTB and LBW infants born to HBsAg-positive mothers recommended by ISIV-NIP-v2016 was not fully implemented. A strong public health intervention should be taken to close the policy-practice gap in China in the future.

Timing of the First Dose of the Hepatitis B Vaccine in Preterm Infants

Introduction: The World Health Organization (WHO) recommends all newborn infants receive the first dose of the hepatitis B vaccine within 24 h of birth irrespective of maternal hepatitis B carrier status. However, the physiological immaturity of the immune system in preterm infants may influence the immune responses to the vaccine particularly in the first few days and weeks of life, and adverse events may occur following vaccination that are not observed in infants born at term. Objectives: To review existing published guidelines surrounding timing of the first dose of the hepatitis B vaccine in preterm infants born to hepatitis B surface antigen negative (HBsAg-negative) mothers. Methods: A search was performed for relevant papers and guidelines published between January 2002 and July 2022 on the Ovid MEDLINE and Embase databases and through targeted searches. Two authors independently reviewed the search results to identify relevant sources, which were then analysed and described through narrative synthesis. Results: Twenty-seven relevant papers and guidelines regarding 15 countries and regions were included. Of these, 13.3% of guidelines, which represented 16.8% of the overall population of 4.1 billion people covered by the identified guidelines, recommended a nationwide birth dose of the hepatitis B vaccine to all preterm infants. In 40.0% of guidelines (77.9% of the overall population), the birth dose was only recommended for infants with a birth weight of more than 2000–2200 g. Another 33.3% of countries and regions (covering 4.4% of the population) recommended no universal birth dose for all infants, including preterm infants, whilst 13.3% (1.0% of the population) had guidelines that varied between jurisdictions and hospitals within their country/region. Conclusions: Existing guidelines surrounding the timing of the first dose of the hepatitis B vaccine in preterm infants vary substantially between countries and regions. Further research comparing the immunogenicity and safety of different hepatitis B vaccine schedules is needed to provide concrete evidence to provide guidance regarding the timing of vaccination against hepatitis B in preterm infants.

Vaccination in preterm and low birth weight infants in India

In India, the high neonatal and infant mortality rate is due in part to an increasing number of preterm and low birth weight (LBW) infants. Given the immaturity of immune system, these infants are at an increased risk of hospitalization and mortality from vaccine-preventable diseases (VPDs). In this narrative review, we screened the scientific literature for data on the risk of VPDs, vaccination delay and factors related to it in Indian preterm and LBW infants. Although routine childhood vaccinations are recommended regardless of gestational age or birth weight, vaccination is often delayed. It exposes these infants to a higher risk of infections, their associated complications, and death. After-birth complications, lack of awareness of recommendations, vaccine efficacy and effectiveness and concerns related to safety are some of the common barriers to vaccination. Awareness campaigns might help substantiate the need for (and value of) vaccination in preterm and LBW infants.

What is the context?

In India, the high neonatal mortality rate is due in part to an increasing number of pretern and low birth weight intants.

Affected infants have a poorly developed inmune system and are more susceptible to contracting vaccine-preventable diseases.

The Indian Academy of Pediatrics recommends vaccination according to the same schedule used for full term infants, following chronological (not gestational) age.

Delays in vaccinations increase the risk of preventable infections.

What is new?

Our review of the scientific literature shows that, in India:

infections have more serious conseuences in preterm and low birth weight infants

delays to vaccinate affected infants are common, mostly due to safety and effectiveness concerns from parents and healthcare pracitionrs.

What is the impact?

Improving mternal nutritional status and immunization, and perinatal care could help reduce the number of preterm and low birth weight infants.

Combining maternal immunization with vaccination of affected infants can confer safe and effective protection.

Awareness campaigns for parents and healthcare practitioners could address the issue of vaccination delay in pretern and low birth weight infants in India.

Japanese original delayed hepatitis B vaccination provides adequate immunogenicity against mother-to-child hepatitis B virus infection in preterm infants: A nationwide survey in Japan

OBJECTIVE

We aimed to evaluate immunogenicity following Japanese original delayed hepatitis B (HB) vaccinations for prevention of mother-to-child HB infection in preterm infants.

METHODS

A nationwide survey in Japan was conducted at certified neonatology facilities in 2014. Eighty-four preterm infants born from a serum hepatitis B surface (HBs) antigen-positive mother were included. We collected data on the following parameters: gestational age, birth weight (BW), age at HB vaccination, age at examination of serum anti-HBs titer, and serum anti-HBs titer. The delayed HB vaccination schedule was 3 doses of HB vaccines at 2, 3 and 5 months of age. A seropositive immunogenic response to HB vaccination was defined as an anti-HBs titer ≥10 mIU/mL. Seropositive rates were calculated in all participants. Four subgroups based on BW were as follows: <1000 g (n = 13), 1000-1499 g (n = 16), 1500-1999 g (n = 26), and ≥2000 g (n = 29).

RESULTS

Among 84 preterm infants who completed the delayed vaccination schedule, 82 (98%) achieved seropositive anti-HBs titer at a median age of 6 months. Seropositive rates of infants <1000 g, 1000-1499 g, 1500-1999 g, and ≥2000 g were 92%, 94%, 100%, and 100%, respectively.

CONCLUSION

The Japanese original delayed HB vaccinations achieved sufficient seropositive rates in preterm infants and provide immunogenicity against mother-to-child HB infection.

Common Queries About Immunizations in Preterm Infants

Preterm infants are at an increased risk of morbidity and mortality from vaccine-preventable diseases. Despite this, delays in routine immunization of preterm infants are common. Available guidelines clearly state that they should be immunized according to chronological age, irrespective of gestational age and birth weight or current weight. In this article, we try to assuage parental and provider doubts by reviewing data about immunogenicity, safety, and responses to routine immunizations in preterm infants with and without comorbidities. We also look at evidence for other strategies to help protect this fragile population. [Pediatr Ann. 2018;47(4):e147-e153.].

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.

Hepatitis B Postexposure Prophylaxis in Preterm and Low-Birth-Weight Infants

Objective Recommendations for immunoprophylaxis in low-birth-weight (LBW) infants born to hepatitis B surface antigen (HBsAg)-positive mothers vary. We successfully immunized an HBsAg-exposed infant (birth weight: 400 g) and performed a literature review on the outcome of postexposure immunoprophylaxis in HBsAg-exposed preterm and LBW infants. Methods By use of PubMed we identified articles relevant to the topic. Studies were included if the intended vaccine schedule was completed and follow-up data were reported. Results Antibody response was reported in 31 LBW infants (birth weight < 2,500 g) and 49 infants with gestational age of < 38 weeks. Low anti-HBs antibody levels (< 100 IU/L) were found in 9 (29%) of the 31 LBW infants. Overall, 2 of 20 (10%) preterm infants and 2 of 17 (12%) LBW were HBsAg-positive on follow-up. In one study, none of the 26 exposed very LBW infants became infected. Conclusion Due to heterogeneity in immunization schedules, lack of information on transmission rates, and the small number of included subjects, no firm conclusions can be drawn regarding the optimal postexposure prophylaxis in LBW infants. We propose that active and passive immunization at birth should be completed by three further active doses (0-1-2-12 month schedule) until further prospective studies are available.

Weight-based policy of hepatitis B vaccination in very low birth weight infants in Taiwan: a retrospective cross-sectional study

Background

The current recommendation of giving the first dose of hepatitis B vaccine to very low birth weight (VLBW) infants at 30 days of chronologic age usually is not practical, because most VLBW infants are not medically stable at that age. We use an alternative body-weight-based protocol, and evaluate its efficacy in an endemic area under a universal immunization program.

Methods

The immunogenicity of the current hepatitis B vaccination strategy in 155 VLBW preterm infants was evaluated at age 2 to 13 years, with parental consent. All of the infants were born between 1995 and 2006, and received their first dose of hepatitis B vaccine when they reached 2,000–2,200 g, irrespective of chronological age. Hepatitis B immunoglobulin (HBIG) was given at birth to infants born to HBsAg(+)/HBeAg(+) mothers.

Results

All 155 of the recruited children were HBsAg and anti-HBc negative. The anti-HBs seropositivity rate (geometric mean titer) was 84.1% (146.5 mIU/mL) for children under 3 years, 73.5% (68.8 mIU/mL) for 4- to 7-year-olds, 27.7% (55.4 mIU/mL) for 8- to 11-year-olds and 20% (6.0 mIU/mL) for children ≥12 years of age. More than 90% of these children received the first vaccination after 30 days of age, half (51%) at 60 to 90 days, and 29 children (18.6%) after 90 days of age. Of the 26 infants born to HBsAg(+) mothers, 6/6 infants of HBeAg(+) mothers received HBIG at birth, and 12/20 infants of HBeAg(−) mothers received HBIG. None of the 26 infants became infected.

Conclusions

Delaying hepatitis B vaccinations in VLBW preterm infants until they reach a weight of 2,000 g, with the administration of HBIG at birth for infants of HBsAg(+) mothers provided adequate immunogenicity and protection in a highly endemic area. Weight-based policy of hepatitis B vaccination is an effective and practical alternative strategy for VLBW infants.

Hepatitis B vaccine response among infants born to hepatitis B surface antigen-positive women

PURPOSE

Annually, an estimated 25,000 infants are born to hepatitis B surface antigen (HBsAg)-positive women in the United States. Hepatitis B (HepB) vaccine and hepatitis B immune globulin (HBIG) are recommended at birth, followed by completion of vaccine series and post-vaccination serologic testing (PVST). In a large cohort of infants born to HBsAg-positive women, factors influencing vaccine response were evaluated.

METHODS

Data were from HBsAg-negative infants born to HBsAg-positive women in the Enhanced Perinatal Hepatitis B Prevention Program (EPHBPP) from 2008 to 2013. Vaccine non-responders were defined as infants with antibody to hepatitis B surface antigen (anti-HBs) <10mIU/mL at PVST after receiving ≥3 vaccine doses. Multivariable analyses modeled statistically significant predictor variables associated with non-response.

RESULTS

A total of 17,951 maternal-infant pairs were enrolled; 8654 HBsAg-negative infants born to HBsAg-positive mothers received ≥3 doses of vaccine with anti-HBs results. 8199 (94.7%) infants responded to a primary HepB series; 199 (94.8%) to a second series. Factors associated with anti-HBs <10mIU/mL included gestational age <37 weeks, vaccine birth dose >12h after birth, timing of final vaccine dose <6 months after birth, receipt of 3 vs. 4 vaccine doses, and PVST interval >6 months from final vaccine dose in bivariate analysis. PVST interval >6 months from final vaccine dose (OR=2.7, CI=2.0, 3.6) was significantly associated with anti-HBs <10mIU/mL; the proportion increased from 2% at 1-2 months to 21.6% at 15-16 months after the final dose. Receipt of a 4th dose improved the response rate (OR=0.5, CI=0.3, 0.8).

CONCLUSIONS

Ninety-five percent of a large cohort of uninfected infants born to HBsAg-positive mothers in the United States responded to primary HepB vaccine series. The proportion of infants with anti-HBs <10mIU/mL increased with longer interval between the final vaccine dose and PVST. Optimal timing of PVST is within 1-2 months of final vaccine dose to avoid unnecessary revaccination.

Seroprotection after recombinant hepatitis B vaccination among newborn infants: a review

INTRODUCTION

Hepatitis B vaccination starting at birth provides a safety net for infants exposed to hepatitis B virus (HBV) during delivery or in early life. Hepatitis B vaccine is recommended in the United States for infants prior to birthing facility discharge, and within the first 12h of life for infants born to hepatitis B surface antigen (HBsAg)-positive mothers. We performed a literature review and summarized the response to recombinant hepatitis B vaccine among infants.

METHODS

Studies published between 1987 and 2011 assessing seroprotection from recombinant hepatitis B vaccine starting within the first 30 days of life were eligible. Seroprotection was defined using an antibody to hepatitis B surface antigen (anti-HBs) threshold of 10mIU/mL at series completion. Infant seroprotection was compared in trial arms varying by maternal hepatitis B antigen status (e antigen [HBeAg], HBsAg), hepatitis B immune globulin (HBIG) administration, birth weight, vaccine dosage, schedule, and age at first dose.

RESULTS

Forty-three studies were included. The median seroprotection proportion overall was 98% (range 52%, 100%). The final median seroprotection proportions did not vary appreciably by maternal HBsAg status, HBIG administration, or schedule. Higher compared to lower dosage resulted in earlier increases in anti-HBs but not in final seroprotection proportions. Infants with birth weights <2000g compared to ≥2000g had lower median seroprotection proportions (93% and 98%, respectively). Median seroprotection proportions were also lower when infants with birth weights <2000g were vaccinated at 0-3 days of age compared to 1 month of age or older (68% versus 95%, respectively).

CONCLUSION

High levels of protection from recombinant hepatitis B vaccine are achieved in term infants vaccinated at birth, effectively preventing transmission of HBV and resultant morbidity and mortality. Implications, if any, for long-term protection are unknown for differences in responses among infants vaccinated at birth compared to ages older than 1 month.

Impact of birth weight at term on rates of emergency room visits and hospital admissions following vaccination at 2 months of age

BACKGROUND

Birth weight of children born at term may theoretically be associated with risk of adverse events from immunization.

METHODS

We analyzed data on children born between April 1st 2002 and March 31st 2009 in the province of Ontario. Using the self-controlled case series design, we examined the risk of the combined endpoint of emergency room visit and hospital admission in the immediate three days post vaccination at 2 months of age compared to a control period 9-18 days after vaccination. In term children, we conducted 4 comparisons of relative incidence (RI) of events: (1) 4 lower birth weight quintiles compared to the largest quintile (2) SGA10 infants compared to non SGA10 infants, (3) low birth weight infants (<2500g) compared to non low birth weight infants and (4) SGA10 infants vaccinated before 60 days compared to those vaccinated after 60 days.

RESULTS

There was a significant trend towards increasing relative incidence of the combined endpoint with decreasing birth weight quintile (p=0.016). There was an increased relative incidence of events in SGA10 versus non SGA10 infants (RI 1.25 (95% CI 1.09-1.44)) and in SGA10 children vaccinated before 60 days of age compared to after 60 days of age (RI 1.57 (95% CI 1.14-2.18)). No significant effect was observed in low birth weight children. The impact of birth weight was primarily mediated through an increase in ER visits in the 24h following vaccination.

CONCLUSION

Lower birth weight appears to be correlated with an increased risk of emergency room visits within 24h of vaccination. The absolute risk is small and there was no impact on admissions or death.

Heptavalent pneumococcal conjugate vaccine immunogenicity in very-low-birth-weight, premature infants

BACKGROUND

The heptavalent pneumococcal CRM197 conjugate vaccine (PCV-7) has been incompletely studied in very-low-birth-weight (< or =1500 g) infants.

OBJECTIVE

To assess PCV-7 immunogenicity in very-low-birth-weight, premature infants. We hypothesized that the frequency of postvaccine antibody concentrations > or =0.15 microg/mL would vary directly with birth weight.

METHODS

This was a multicenter observational study. Infants 401 to 1500 g birth weight and <32 0/7 weeks gestation, stratified by birth weight, were enrolled from 9 National Institute of Child Health and Human Development Neonatal Research Network centers. Infants received PCV-7 at 2, 4, and 6 months after birth and had blood drawn 4 to 6 weeks following the third dose. Antibodies against the 7 vaccine serotypes were measured by enzyme-linked immunosorbent assay.

RESULTS

Of 369 enrolled infants, 244 completed their primary vaccine series by 8 months and had serum obtained. Subjects were 27.8 +/- 2.2 (mean +/- standard deviation) weeks gestation and 1008 +/- 282 g birth weight. Twenty-six percent had bronchopulmonary dysplasia and 16% had received postnatal glucocorticoids. Infants 1001 to 1500 g birth weight were more likely than those 401 to 1000 g to achieve antibody concentrations > or =0.15 microg/mL against the least 2 immunogenic serotypes (6B: 96% vs. 85%, P = 0.003 and 23F: 97% vs. 88%, P = 0.009). In multiple logistic regression analysis, lower birth weight, postnatal glucocorticoid use, lower weight at blood draw, and Caucasian race were each independently associated with antibody concentrations <0.35 microg/mL against serotypes 6B and/or 23F.

CONCLUSIONS

When compared with larger premature infants, infants weighing < or =1000 g at birth have similar antibody responses to most, but not all, PCV-7 vaccine serotypes.

Low hepatitis B immunogenicity of a hexavalent vaccine widely used in Germany: results of the German Health Survey for Children and Adolescents, 2003–2006

The success of childhood vaccination against hepatitis B relies on persistence of immunity into adolescence and adulthood. In 2000, two hexavalent vaccines with a hepatitis B component (Hexavac®, Infanrix hexa®) were introduced in Germany. Hexavac was withdrawn in 2005 amidst concerns about its long-term hepatitis B protection. We compared hepatitis B surface antibody (anti-HBs) levels in children fully vaccinated with Hexavac or Infanrix hexa (n=477) in a secondary data analysis of a large cross-sectional health survey in Germany. On average 2·4 years after vaccination, 25·3% of Hexavac vaccinees had anti-HBs levels <10 mIU/ml (95% CI 19·0–32·8) compared to 4·7% of Infanrix hexa vaccinees (95% CI 2·4–8·9). These findings suggest that short-term hepatitis B immunogenicity in Hexavac vaccinees may also be weaker. Further studies are warranted to assess whether Hexavac vaccinees should be re-vaccinated or receive a booster vaccination before these birth cohorts reach adolescence.

HEPATITIS B AND PREGNANCY, THE SCIENTIFIC BASIS FOR PERINATAL PREVENTION

Hepatitis B and its complications are one of the major global health problems. Around 2 billion individuals are infected by hepatitis B virus (HBV) worldwide, more than 350 million are chronically infected, and approximately 15 to 40 percents of them will develop serious complications such as liver cirrhosis, hepatic failure, or hepatocellular carcinoma (HCC). The worldwide prevalence of chronic HBV infection ranges from 0.1 to 20 percent and varies widely in different geographic areas. According to the prevalence rate, WHO has classified countries into 3 levels: high areas (>8%) such as Africa, Asia, Western Pacific and Middle East; intermediate areas (2–8%) such as South America and Eastern Europe, and low areas (<2%) such as Western Europe, North America, and Australia.

Vaccines and preterm neonates: why, when, and with what

This review analyses what is known concerning the immune response of preterm (PTIs) and low birth weight infants (LBWIs) to widely used vaccines, the protection they receive from routine immunisation, and the safety and tolerability of the vaccines themselves. It shows why PTIs and LBWIs should be vaccinated using the same schedules as those usually recommended for full-term infants (FTIs), except in the case of hepatitis B vaccine, whose schedule should be repeated in infants who received the first dose during the first days of life when they weighed less than 2000 g because of their reduced immune response. Vaccines are immunogenic, safe and well tolerated in PTIs and LBWIs, in whom early active immunisation is particularly important because they are among the most vulnerable subjects for pediatric infectious diseases. It is therefore essential to make every effort to convince pediatricians and parents that compliance with these recommendations will not cause any clinical problems.

Hepatitis B vaccination: The key towards elimination and eradication of hepatitis B

Hepatitis B virus infection is a global health problem. Worldwide, about 360 million people are chronically infected with the virus. They continue to spread the virus to others and are themselves at risk of chronic liver diseases and hepatocellular carcinoma. The infection can now be treated by antivirals or interferons and the transmission route can be interrupted. Nevertheless, the most effective means is to immunize all susceptible individuals, especially young children, with safe and efficacious vaccines. The combined efforts of vaccination, effective treatment and interruption of transmission make elimination of the infection plausible and may eventually lead to eradication of the virus. Because hepatitis B vaccination has a key role in the control of hepatitis B, properties of this vaccine, its effectiveness in pre-exposure and post-exposure settings, duration of protection after vaccination and the need of booster doses are discussed. Mass hepatitis B vaccination in children decreases the carriage of the virus, and the diseases associated with acute and chronic infection, including hepatocellular carcinoma. Challenges that need to be solved to expand mass vaccination, and the strategies towards elimination and eventual eradication of hepatitis B in the world are also discussed.

Immunogenicity and reactogenicity of DTPa-HBV-IPV/Hib vaccine as primary and booster vaccination in low-birth-weight premature infants

AIM

To assess suitability of a combined DTPa-HBV-IPV/Hib vaccine (Infanrix hexa) for immunization of low-birth-weight (<2.0 kg) preterm infants, with particular focus on the hepatitis B response.

METHODS

Open-label study in 170 preterm infants receiving primary vaccination at 2, 4 and 6 months of age and booster vaccination at 18-24 months. Enrollment and analysis were stratified in two groups: infants with birth weight between 1.5 kg and 2.0 kg (low birth weight: LBW), infants with BW <1.5 kg (very low birth weight: VLBW).

RESULTS

One month after the three dose primary vaccination, 93.7% and 94.9% of infants in VLBW and LBW groups, respectively, had anti-HBs antibody concentrations > or = 10 mIU/mL. High seroprotection and response rates (92.4-100%) to all vaccine antigens were observed. Those were reinforced (>98%) by booster vaccination for all antigens except for HBs in VLBW children: only 88.7% of those had anti-HBs antibody concentrations > or = 10 mIU/mL, compared with 96.5% of LBW children (difference statistically not significant). The vaccine was well tolerated in both groups of infants.

CONCLUSION

Preterm infants will benefit by the administration of a primary and booster vaccination with DTPa-HBV-IPV/Hib vaccine.

[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.

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.

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.

Hepatitis B vaccination is effective for babies weighing less than 1800 g

AIM

This trial studied the effectiveness of early hepatitis B (HepB) immunisation in babies weighing less than 1800 grams, born of HepB surface-antigen-negative mothers.

METHODS

The first vaccine dose was given once clinical stability was achieved, with second and third doses given 1 and 6 months later, respectively. HepB serology, done using Abbott ElA (phase 1) and Abbott Axsym (phase 2) before and after June 2001, respectively, was checked at birth (Sero1), prior to (Sero2) and 6 months after (Sero3) the third dose. A booster dose was recommended when Sero3 showed a non-immune status (< 10 mIU/mL).

RESULTS

Median birth weight and gestational age (n = 118) were 1295 [range 475, 1780] g and 31 [range 24, 37] completed weeks, respectively. Sero1 (median age of 4 [range 1, 34] days) showed 64% (n = 113) to be non-immune. The first dose of vaccine was administered at a median weight of 1268 [range 530, 1790] g, median age of 6 [range 1-63] days and median post-menstrual age of 32 [range 24-37] completed weeks. Sero2 (median age of 179 [range 112-260] days), for 110 babies (93.2%) showed immunity in 48.2% (median titres--Phase 1: 26 [range 10, 150] mIU/mL; Phase 2: 34 [range 10, 1000] mIU/mL). Sero3 revealed seroprotection in 77.8% (median titres--Phase 1: 102 [range 12, 150] mIU/mL; Phase 2: 162 [range 16, 1000] mIU/mL). The more mature the bady at time of first dose, the more likely he is to achieve seroprotection (85% amongst those administered at and beyond 33 weeks; 91% among those administered at and beyond Day 10 at Sero3).

CONCLUSIONS

Early HepB immunisation in infants < 1800 g can be safely recommended, with booster doses necessary at 1 year for some infants.

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.

Response of preterm newborns to immunization with a hexavalent diphtheria-tetanus-acellular pertussis-hepatitis B virus-inactivated polio and Haemophilus influenzae type b vaccine: first experiences and solutions to a serious and sensitive issue

OBJECTIVE

Preterm infants are at increased risk from infections and should be vaccinated at the usual chronological age. The aim of the study was to evaluate the immunogenicity and reactogenicity of a hexavalent diphtheria-tetanus-acellular pertussis-hepatitis B virus-inactivated polio and Haemophilus influenzae type b (DTPa-HBV-IPV/Hib) vaccine in preterm infants.

METHODS

In a comparative trial, 94 preterm infants between 24 and 36 weeks (mean +/- SD gestational age: 31.05 +/- 3.45 weeks; mean birth weight: 1420 +/- 600 g) and a control group of 92 full-term infants were enrolled to receive 3 doses of a DTPa-HBV-IPV/Hib vaccine at 2, 4, and 6 months. Immunogenicity was assessed in serum samples that were taken before and 4 weeks after primary vaccination. Evaluation of reactogenicity was based on diary cards.

RESULTS

All preterm (n = 93) and full-term (n = 89) infants who were included in the immunogenicity analysis had seroprotective titers to diphtheria; tetanus; and polio virus types 1, 2, and 3. The immune response to the Hib and hepatitis B components was lower in preterm than in full-term infants: 92.5% versus 97.8% and 93.4% versus 95.2%, respectively. Vaccine response rates for pertussis antigens were >98.9% in both study groups. Although most geometric mean titers were lower in preterm infants, titers were similar for pertussis, a major threat for premature infants. The vaccine was well tolerated, and there were no differences in reactogenicity between groups. Some extremely immature infants experienced transient cardiorespiratory events within the 72 hours after the first vaccination with no clinical repercussion.

CONCLUSIONS

Preterm infants who were immunized with the hexavalent DTPa-HBV-IPV/Hib vaccine at 2, 4, and 6 months displayed good immune response to all antigens. The availability of this vaccine greatly facilitates the vaccination of premature infants.

Recombivax-HB: perspectives past, present and future

Hepatitis B disease has caused a heavy burden worldwide. The development of an immunogenic, efficacious and safe vaccine to combat this problem has already eased this burden to some extent. The incorporation of the vaccine into the infant and childhood immunization schedule has led to a decrease in the number of new hepatitis B cases reported each year, and there has been a significant decline in hepatocellular carcinoma in children. This implies that the future will see less hepatitis B disease as the infant and adolescent population that has been immunized ages, meaning that the disease burden should fall even further.

Immunization of preterm and low birth weight infants. American Academy of Pediatrics Committee on Infectious Diseases

Preterm (PT) infants are at increased risk of experiencing complications of vaccine-preventable diseases but are less likely to receive immunizations on time. Medically stable PT and low birth weight (LBW) infants should receive full doses of diphtheria, tetanus, acellular pertussis, Haemophilus influenzae type b, hepatitis B, poliovirus, and pneumococcal conjugate vaccines at a chronologic age consistent with the schedule recommended for full-term infants. Infants with birth weight less than 2000 g may require modification of the timing of hepatitis B immunoprophylaxis depending on maternal hepatitis B surface antigen status. All PT and LBW infants benefit from receiving influenza vaccine beginning at 6 months of age before the beginning of and during the influenza season. All vaccines routinely recommended during infancy are safe for use in PT and LBW infants. The occurrence of mild vaccine-attributable adverse events are similar in both full-term and PT vaccine recipients. Although the immunogenicity of some childhood vaccines may be decreased in the smallest PT infants, antibody concentrations achieved usually are protective.

Hib vaccination in infants born prematurely

AIMS

To document the immunogenicity and persistence of antibody to polyribosyl-ribitol phosphate (PRP) as well as the clinical protection against invasive Haemophilus influenzae type b (Hib) disease in premature infants immunised at the routine schedule.

METHODS

Blood was obtained at 2, 5, 12, and 64 months of age from a cohort of prematurely born infants (<or=32 weeks gestation). Anti-PRP antibody concentrations were compared with those of a control cohort of infants born at full term and vaccinated at the same schedule. Hib vaccine failures occurring between October 1992 and October 2000 were reported by paediatricians through an active, prospective, national survey in the UK and Republic of Ireland. The number of prematurely born children with vaccine failure was compared with the corresponding number born at term.

RESULTS

Twenty seven prematurely born infants were followed to 5 years of age. Compared with term infants they had a significantly lower geometric mean concentration of anti-PRP antibody and/or a significantly lower proportion above one or both of the conventional protective antibody concentrations (0.15 and 1.0 micro g/ml) at all ages. A total of 165 cases of invasive Hib disease were identified over eight years of national surveillance. Eighteen were premature (<37 weeks); approximately 12 would be expected. The relative risk of UK premature infants developing disease compared with term infants was 1.5 (95% CI 0.9 to 2.6).

CONCLUSIONS

Premature infants develop lower antibody concentrations than term infants following Hib conjugate vaccination. Premature infants may also have an increased risk of clinical vaccine failure, but interpretation is limited by the small number of premature infants developing invasive Hib disease over eight years of national surveillance. Overall, vaccination with Hib conjugate vaccines affords a high level of protection to premature babies.

Efficacy, immunogenicity and safety of heptavalent pneumococcal conjugate vaccine in low birth weight and preterm infants

OBJECTIVE

To determine the efficacy, immunogenicity and safety of the heptavalent CRM197 pneumococcal conjugate vaccine (PCV) in low birth weight (LBW) and preterm (PT) infants against invasive pneumococcal disease caused by vaccine types.

METHODS

In a randomized double blind trial of 37,868 infants given either PCV or meningococcal type C conjugate vaccine (MCV), 1756 infants <750 g <2500 g (LBW) and 4340 infants from 32 to <38 weeks old (PT) were identified. Risk of invasive pneumococcal disease in LBW and PT infants was compared with risk in normal birth weight (NBW) and full term (FT) infants. Local and systemic events observed within 48 h of recent vaccine were assessed by telephone interviews and similar comparisons made. Premature infant Emergency Department visits and hospitalization were also identified and compared with FT and NBW infants.

RESULTS

Initiation of immunization and intervals between doses were similar for all groups. The risk ratio for invasive pneumococcal diseases for LBW infants compared with NBW infants was 2.6 (P = 0.03), and for PT compared with FT infants the risk ratio was 1.6 (P = 0.06). Vaccine efficacy for both groups was 100%. PCV was as immunogenic in LBW and PT as in NBW and FT infants. Fever and local events after PCV vaccination were similar when adjusted for clustering among multiple doses per child. When stratified for individual doses there was more redness and swelling for LBW infants and more swelling for PT infants after Dose 3. Isolated local and systemic reactions were more commonly seen with PCV than with MCV, a pattern similar to that in NBW and FT infants. Hospitalization rates were similar for PCV and MCV recipients.

CONCLUSION

These data support the use of PCV in LBW infants and PT infants.

Seven-year follow-up of vaccine response in extremely premature infants

OBJECTIVE

To assess the immune response of 7-year-old former extremely preterm (PT) infants to routine childhood immunizations.

METHODS

Sixteen PT (<29 weeks and <1000 g) infants, followed since their primary immunizations at the recommended chronological ages, and 16 age-matched full-term (FT) control subjects were evaluated at 7 years of age. Antibodies to Haemophilus influenzae type b polyribosylribitol phosphate (Hib-PRP), tetanus, pertussis, diphtheria, polio, and hepatitis B (HBsAb) were measured.

RESULTS

The FT group had higher antidiphtheria geometric mean titers (GMT) than the PT group (1.07 vs 0.36 IU/mL). All FT and 13 of 16 PT had protective diphtheria antibody titers (>0.1 IU/mL). The tetanus GMT were 4.22 IU/mL (FT) and 1.99 IU/mL (PT). All children had protective tetanus titers (>0.01 IU/mL). Pertussis titers did not differ between FT and PT. Hib-PRP GMT were higher in FT than in PT (3.21 vs 1.41 microg/mL). All children had anti-PRP > or = 0.15 microg/mL; 12 of 16 FT and 10 of 16 PT had levels > or = 1.0 microg/mL. Polio serotype 1 and 2 GMT were similar between groups, and all children had protective titers (> or = 8). Polio serotype 3 GMT were 59 (FT) and 24 (PT) Karber units; all FT and 12 of 16 PT had protective titers. Among children who had received hepatitis B vaccine, GMT were similar in FT and PT children (120 vs 186 mIU/mL, and similar proportions of children (11 of 16 FT and 12 of 14 PT) had protective HBsAb titers (>10 mIU/mL).

CONCLUSIONS

At 7 years of age, PT children had lower antibody titers to many vaccine antigens than FT children. However, most PT children maintained antibody titers in the protective range.

Immunogenicity of hepatitis B vaccine in preterm and full term infants vaccinated within the first week of life

The immunogenicity of a Hepatitis B vaccine was evaluated in 110 neonates (57 full term and 53 preterm) born to Hepatitis B surface antigen (HBsAg) negative mothers. Three 10 microg doses of recombinant Hepatitis B vaccine were administered: the first dose within the first week of life; the second between 1 and 2 months; and the third at 5-7 months of age. Anti-HBs antibody titres were measured 3 months after the third dose. The seroconversion rate in preterm infants (77%; 95% CI=64.7-87.1) was significantly lower than in full term infants (98%; 95% CI=91.6-99.9) while the mean anti-HBs titres among those infants that did seroconvert was lower in preterm (186.6 mIU ml(-1)) than in full term infants (537.5 mIU ml(-1)). More full term than preterm infants showed titres greater than 100 mIU ml(-1) (71.9 and 41.5%, respectively). We conclude that the administration of a recombinant Hepatitis B vaccine shortly after birth is less immunogenic in preterm infants weighing <1800 g at birth than in full term infants. Currently accepted recommendations for post exposure perinatal prophylaxis may be inadequate to protect preterm infants.

Controlled trial of immune response of preterm infants to recombinant hepatitis B and inactivated poliovirus vaccines administered simultaneously shortly after birth

AIM

The study was conducted to evaluate the immunogenicity of an early, extra dose of enhanced inactivated poliovirus vaccine (IPV) administered simultaneously with recombinant hepatitis B vaccine (HBV) to preterm infants shortly after birth.

METHODS

Three groups were studied. Fifty preterm infants received IPV intramuscularly within 24 hours of birth, in addition to routine recommended childhood immunisations. Fifty two preterm infants and 35 full term infants received routine immunisations only (routine vaccination timing: HBV at birth, 1 and 6 months of age; IPV at 2 and 4 months; oral polio vaccine (OPV) at 4 and 6 months; diphtheria-tetanus-pertussis (DTP) at 2, 4, and 6 months; and Haemophilus influenzae B vaccine at 2 and 4 months). Blood samples were taken at birth, 3 and 7 months of age from all infants, and at 1 month of age from preterm infants only.

RESULTS

At birth, a lower percentage of both study and control preterm infants had antipoliovirus type 3 titres >/= 1:8 than full term infants. At 1 and 3 months of age significantly more early IPV infants had antipoliovirus type 3 titres >/= 1:8 than routinely vaccinated preterm infants (p < 0.05). At 7 months of age there were no significant differences in percentage of antipoliovirus titres >/= 1:8 or geometric mean times (GMTs) between the early IPV group and the routinely vaccinated preterm group. At 3 and 7 months of age, the percentage of positive antihepatitis B titres (>/= 1:10) and the GMT of the early IPV preterm group did not differ significantly from those of preterm controls. There was no significant difference in percentage of positive antihepatitis B titres between the early IPV group and full term controls at any time. GMTs for hepatitis B antibodies were significantly lower in the early IPV preterm group than in full term controls at 3 and 7 months of age.

CONCLUSIONS

Administration of an additional dose of IPV simultaneously with routine HBV to preterm infants shortly after birth provides early protection from poliovirus and hepatitis B infection, and does not interfere with poliovirus antibody production at the age of 7 months.

Current update of pediatric hepatitis vaccine use

Vaccines are now available for the prevention of hepatitis A and hepatitis B. In this article, biologics are reviewed with special attention to their use in the pediatric patient. Special attention is paid to issues that developed in 1999. For hepatitis A vaccine, it is the change in US recommendations regarding increased use in higher-risk US locations. For hepatitis B vaccine, it is the concern about toxicity, real or imagined.

Immunogenicity of plasma-derived hepatitis B vaccine in preterm infants

The objective was to determine whether plasma-derived hepatitis B vaccine is immunogenic in preterm appropriate for gestation babies when administered at birth and to compare the immunogenicity between 5 micrograms and 10 micrograms doses of the vaccine in these babies. Fifty preterm neonates (31-36 weeks gestation) were randomized to receive 5 micrograms or 10 micrograms doses of plasma-derived hepatitis B vaccine at birth, with subsequent doses 1 and 6 months later. Serum specimens were obtained a month after each dose of the vaccine and were tested for antibody to hepatitis B surface antigen (anti-HBs). Thirty six babies (gestation 31-36 weeks), 18 from each group competed the study. While 89.2% of the babies seroconverted, 82.1% achieved seroprotective titres of anti-HBS (> 10 mIU/ml). There was no difference between weight, gestational age, age of administration of vaccine and age of estimation of anti-HBs between 5 micrograms and 10 micrograms groups. The difference in the seroprotective rates were not statistically different between the groups (5 micrograms 78.5%; 10 micrograms--85.7%). Although immune response to plasma derived hepatitis B vaccine in preterm babies is suboptimal when the first dose is administered at birth, the full course achieves adequate seroprotective levels.

Hepatitis B vaccination of premature infants: a reassessment of current recommendations for delayed immunization

OBJECTIVE

Current American Academy of Pediatrics and United States Public Health Service Immunization Practices Advisory Committee recommendations for hepatitis B immunization in premature infants weighing <2 kg at birth born to hepatitis B surface antigen (HBSAg)-negative mothers are to delay the initiation of vaccination until such infants reach 2 kg or until 2 months of age. This proposal to delay vaccination at birth in these low-risk infants was based on limited studies not conducted in the United States. We sought to reassess current recommendations to delay administration of hepatitis B vaccine in low-risk premature infants by determining the immunogenicity of early hepatitis B vaccination in a US population and identifying variables associated with poor immunogenicity.

METHODS

A total of 148 infants <37 weeks' gestation born to mothers negative for HBSAg were recruited at birth and stratified to three birth weight groups: <1000 g, 1000 to 1500 g, and >1500 g. Recombinant hepatitis B vaccine was administered within the first week of life, at 1 to 2 months of age, and at 6 to 7 months of age. Serum obtained at birth and after the second and third doses of vaccine was tested for antibody to HBSAg. Variables associated with poor response were sought prospectively by collecting demographic and clinical data.

RESULTS

A total of 118 subjects (83%) completed the study. Postsecond dose sera were available for 117 infants and postthird dose sera were available for 112 infants. The seroprotection rate (attaining >/=10 mIU/mL HBS antibody) after two doses was low (25%) regardless of birth weight; infants weighing <1000 g at birth had the poorest response (11%). The seroprotection response rate after three doses of vaccine increased with birth weight; infants weighing </=1500 g at birth (groups 1 and 2) had lower rates of response (52% and 68%, respectively) than did infants weighing >1500 g at birth (group 3; 84% response rate). The seroprotection response rate of group 3 infants after three doses of vaccine, although low, could not be differentiated from the response rates reported for full-term infants using 95% confidence intervals. Of all infants who did not achieve protective levels of antibody after three doses of vaccine, 96% (26/27) weighed <1700 g at birth. The geometric mean HBS antibody levels in responders were 88 and 386 mIU/mL after two and three doses, respectively. Of 36 children with a birth weight >1500 g, 33 (91%) achieved levels of HBS antibody >100 mIU/mL after three doses of vaccine, compared with 25/35 (71%) of infants with birth weight <1500 g. Using logistic regression analysis, nonresponders were more likely than were responders to have been treated with steroids (26% vs 9%) and to have had a low birth weight (1037 g vs 1455 g). In addition, the seroresponse rate of black infants was more likely than that of white infants to be associated with poor weight gain (falling off 2 percentile ranks in weight) in the first 6 months of life: 22% of black and 60% of white children who failed to gain weight adequately responded to vaccination, compared with 92% of black and 70% of white children who were growing adequately. Of interest, the only infant with a birth weight of >1700 g who did not make protective levels of specific antibody after three doses of vaccine was 2300 g at birth, but had inadequate weight gain in the first 6 months of life.

CONCLUSIONS

This study supports current recommendations of the American Academy of Pediatrics and the Centers for Disease Control and Prevention for delaying the initiation of hepatitis B immunization beyond the first week of life for premature infants at low risk for hepatitis B infection, particularly in newborns weighing <1700 g at birth. In addition, we have identified variables other than birth weight that were associated with an inadequate immune response to early hepatitis B vaccination in premature infants, such as poor weight gain in the first 6 months of life