Timeliness of immunisations in preterm infants in the Netherlands

Effect of Palivizumab Prophylaxis on Respiratory Syncytial Virus Infection in Very Preterm Infants in the First Year of Life in The Netherlands

Respiratory Syncytial Virus (RSV) poses a severe threat to infants, particularly preterm infants. Palivizumab, the standard preventive prophylaxis, is primarily utilized in high-risk newborns due to its cost. This study assessed palivizumab's effectiveness in preventing RSV infections in predominantly very preterm infants during their first year of life. Serum samples from a prospective multicentre cohort study in the Netherlands were analyzed to assess RSV infection rates by measuring IgG levels against three RSV proteins: nucleoprotein, pre-fusion, and post-fusion protein. Infants were stratified based on gestational age (GA), distinguishing very preterm (≤32 weeks GA) from moderate/late preterm (>32 to ≤36 weeks GA). In very preterm infants, palivizumab prophylaxis significantly reduced infection rates (18.9% vs. 48.3% in the prophylaxis vs. non-prophylaxis group. Accounting for GA, sex, birth season, and birth weight, the prophylaxis group showed significantly lower infection odds. In infants with >32 to ≤36 weeks GA, the non-prophylaxis group (55.4%) showed infection rates similar to the non-prophylaxis ≤32-week GA group, despite higher maternal antibody levels in the moderate/late preterm infants. In conclusion, palivizumab prophylaxis significantly reduces RSV infection rates in very premature infants. Future research should explore clinical implications and reasons for non-compliance, and compare palivizumab with emerging prophylactics like nirsevimab aiming to optimize RSV prophylaxis and improve preterm infant outcomes.

Measles, mumps, and rubella vaccine at age 6 months and hospitalisation for infection before age 12 months: randomised controlled trial

OBJECTIVE

To test for potential non-specific effects of an additional, early measles, mumps, and rubella (MMR) vaccine at age 5-7 months on risk of infection related hospitalisation before age 12 months.

DESIGN

Randomised, double blinded, placebo controlled trial.

SETTING

Denmark, a high income setting with low exposure to MMR.

PARTICIPANTS

6540 Danish infants aged 5 to 7 months.

INTERVENTIONS

Infants were randomly allocated 1:1 to intramuscular injection with standard titre MMR vaccine (M-M-R VaxPro) or placebo (solvent only).

MAIN OUTCOME MEASURES

Hospitalisations for infection, defined as all hospital contacts of infants referred from primary care for hospital evaluation and with an infection diagnosed, analysed as recurrent events, from randomisation to 12 months of age. In secondary analyses implications of censoring for date of subsequent diphtheria, tetanus, pertussis, polio, Haemophilus influenzae type B, and immunisation with pneumococci conjugate vaccine (DTaP-IPV-Hib+PCV), potential effect modification by sex, prematurity (<37 weeks' gestation), season, and age at randomisation were tested, and the secondary outcomes of hospitalisations ≥12 hours and antibiotic use were evaluated.

RESULTS

6536 infants were included in the intention-to-treat analysis. 3264 infants randomised to MMR vaccine experienced 786 hospitalisations for infection before age 12 months compared with 762 for the 3272 infants randomised to placebo. In the intention-to-treat analysis the rate of hospitalisations for infection did not differ between the MMR vaccine and placebo groups (hazard ratio 1.03, 95% confidence interval 0.91 to 1.18). For infants randomised to MMR vaccine compared with those randomised to placebo, the hazard ratio of hospitalisations for infection with a duration of at least 12 hours was 1.25 (0.88 to 1.77), and for prescriptions of antibiotics was 1.04 (0.88 to 1.23). No significant effect modifications were found by sex, prematurity, age at randomisation, or season. The estimate did not change when censoring at the date infants received DTaP-IPV-Hib+PCV after randomisation (1.02, 0.90 to 1.16).

CONCLUSION

Findings of this trial conducted in Denmark, a high income setting, do not support the hypothesis that live attenuated MMR vaccine administered early to infants aged 5-7 months decreases the rate of hospitalisations for non-targeted infection before age 12 months.

TRIAL REGISTRATION

EU Clinical Trials Registry EudraCT 2016-001901-18 and ClinicalTrials.gov NCT03780179.

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.

Delayed Start of Routine Vaccination in Preterm and Small-for-Gestational-Age Infants: An Area-Based Cohort Study from the Tuscany Region, Italy

Preterm and small-for-gestational-age (SGA) infants are more susceptible to vaccine-preventable diseases. To evaluate routine vaccination timeliness in these high-risk groups, a full birth cohort of infants (n = 41,502) born in 2017 and 2018 in Tuscany was retrospectively followed up until 24 months of age. Infants were classified by gestational age (GA) and SGA status. The vaccinations included: hexavalent (HEXA), measles-mumps-rubella, varicella, pneumococcal conjugate (PCV), and meningococcal C conjugate. Time-to-event (Kaplan–Meier) analyses were conducted to evaluate the timing of vaccination according to GA; logistic models were performed to evaluate the associations between GA and SGA with vaccination timeliness. Time-to-event analyses show that the rate of delayed vaccine receipt increased with decreasing GA for all the vaccinations, with a less marked gradient in later vaccine doses. Compared to full-term infants, very preterm infants significantly showed an increased odds ratio (OR) for delayed vaccination in all the vaccinations, while moderate/late preterm infants only showed an increased OR for HEXA-1, HEXA-3, PCV-1, and PCV-3. SGA infants had a significantly higher risk of delayed vaccination only for HEXA-1 and PCV-1 compared to non-SGA infants. In conclusion, vaccinations among preterm and SGA infants showed considerable delay. Tailored public health programs to improve vaccination timeliness are required in these high-risk groups.

Do Pediatricians and Nurses Recommend Vaccines for Preterm Infants? A Survey in Italy

OBJECTIVE

To assess the level of knowledge, attitudes, and behaviors regarding vaccination in preterm infants among primary care pediatricians (PCPs) and health care workers (HCWs) in neonatal intensive care units (NICUs).

STUDY DESIGN

Data were collected from PCPs through a confidential questionnaire distributed by email, whereas the research team distributed a self-administered anonymous questionnaire to all HCWs working in the selected NICUs.

RESULTS

Overall, 64.1% of HCWs consider vaccines in preterm infants to be very safe. The majority of HCWs (69.8%) stated that they always recommend that preterm infants' parents vaccinate their children following the same schedule as for term infants. This behavior was significantly more likely among those who know that the vaccination schedule for preterm infants is the same as for term infants, who consider vaccines in preterm infants very effective, and who strongly agree that preterm infants should be vaccinated on the same schedule as term infants. Moreover, PCPs were more likely than NICU pediatricians to always recommend that preterm infants' parents vaccinate their children following the immunization schedule of term infants, whereas this behavior was significantly less frequent among NICU nurses.

CONCLUSIONS

There is a need for physicians and nurses in the NICU and in the community to counteract missed or delayed immunizations. Engagement of HCWs in healthcare quality improvement initiatives focused on the promotion of timely vaccinations in preterm infants should be encouraged.

In-hospital and web-based intervention to counteract vaccine hesitancy in very preterm infants' families: a NICU experience

BACKGROUND

Vaccine hesitancy is a global problem, carrying significant health risks for extremely vulnerable population as that of preterm infants. Social media are emerging as significant tools for public health promotion. Our aim was to evaluate both the coverage and the timeliness of routine immunizations in a cohort of preterm infants (< 33 weeks of gestational age) at 24 months of age whose families have been subjected to in-hospital and web-based interventions to counteract vaccine hesitancy.

METHODS

For a period of 2 years parents of preterm infants were instructed during their follow up visits by a member of the NICU team to get correct informations about vaccines from a social network page. Vaccination rates of preterm infants were assessed at 24 months of chronological age with an electronic database and compared to both general population and historical cohort.

RESULTS

Coverage and timeliness of vaccinations at 24 months of age of 170 preterm infants were analyzed in December 2019. Gestational age and birth weight median (IQR) were, respectively, 31.0 (5.0) weeks and 1475.0 (843.8) g. Coverage rates were similar to those of the regional population (p > 0.05), while timeliness of administration was significantly delayed compared to the recommended schedule (p < 0.001). Age of administration was not correlated with either body weight and gestational age at birth (Spearman rank, p > 0.05). DTaP-IPV-HBV-Hib 2nd and 3rd doses, MMR and Varicella vaccines coverage data were higher compared to historical cohort (p < 0.05).

CONCLUSION

Increasing vaccine confidence through web-based interventions could have a positive impact on vaccination acceptance of parents of preterm infants, although timeliness results still delayed. There is a strong need to develop different and effective vaccination strategies to protect this very vulnerable population.

Vaccination timeliness and completeness among preterm and low birthweight infants: a national cohort study

Vaccinating premature and low birthweight (LBW) infants according to chronological age has been found safe and effective. Although these infants are susceptible to infections, vaccinations are often delayed. We estimated vaccination coverage (VC) in preterm and LBW infants compared to term infants in a cohort study (2016 Israel birth cohort, n = 181,543) using the National Immunization Registry. Vaccinations included Hepatitis B, Diphtheria-Tetanus-acellular Pertussis-IPV-Haemophilus influenzae B, Oral Polio Bivalent, Rotavirus, Pneumococcal Conjugate, Measles-Mumps-Rubella-Varicella and Hepatitis A. Inclusion criteria: (1) born in Israel; (2) having a unique identifier (allowing data matching); and (3) surviving to 24 months. VC at 24 months and timeliness of vaccine doses were evaluated according to infants' birthweight (BW) and gestational age (GA). Preterm infants (GA < 37 weeks) comprised 7.0% (n = 12,264); LBW infants (BW< 2500 g) were 7.7% (n = 13,950); BW was 1500-2499 g in 6.8%, 1000-1499 g in 0.6% and below 1000 g in 0.3%. Compared to normal birthweight (NBW) infants (BW≥2500 g), LBW infants showed delayed initiation of vaccinations. Odds ratio (OR) for delay: DTaP-IPV-Hib 1 OR = 1.26 [95%CI 1.19-1.33]; Rota 1, OR = 1.22 [95%CI 1.16-1.29]. Vaccination delay rates were higher among smaller new-borns (below 1000 g). At 24 months there was no significant difference regarding vaccination status. This national cohort VC analysis focused on preterm/LBW infants. Vaccinating preterm and LBW infants according to the recommended schedule induces protection against life-threatening infectious diseases. Vaccination initiation among LBW infants showed considerable delay. Health practitioners and parents should cooperate to improve timely vaccination initiation.

The Fifth International Neonatal and Maternal Immunization Symposium (INMIS 2019): Securing Protection for the Next Generation

Despite significant progress in reaching some milestones of the United Nations Sustainable Development Goals, neonatal and early infant morbidity and mortality remain high, and maternal health remains suboptimal in many countries. Novel and improved preventative strategies with the potential to benefit pregnant women and their infants are needed, with maternal and neonatal immunization representing effective approaches. Experts from immunology, vaccinology, infectious diseases, clinicians, industry, public health, and vaccine-related social sciences convened at the 5th International Neonatal and Maternal Immunization Symposium (INMIS) in Vancouver, Canada, from 15 to 17 September 2019. We critically evaluated the lessons learned from recent clinical studies, presented cutting-edge scientific progress in maternal and neonatal immunology and vaccine development, and discussed maternal and neonatal immunization in the broader context of infectious disease epidemiology and public health. Focusing on practical aspects of research and implementation, we also discussed the safety, awareness, and perception of maternal immunization as an existing strategy to address the need to improve maternal and neonatal health worldwide. The symposium provided a comprehensive scientific and practical primer as well as an update for all those with an interest in maternal and neonatal infection, immunity, and vaccination. The summary presented here provides an update of the current status of progress in maternal and neonatal immunization.

Association of Routine Infant Vaccinations With Antibody Levels Among Preterm Infants

IMPORTANCE

The standard schedule of national immunization programs for infants may not be sufficient to protect extremely and very preterm infants.

OBJECTIVE

To evaluate the immunogenicity of routine vaccinations administered to preterm infants.

DESIGN, SETTING, AND PARTICIPANTS

A multicenter, prospective, observational cohort study of preterm infants stratified according to gestational age recruited from 8 hospitals across the Netherlands between October 2015 and October 2017, with follow-up until 12 months of age (October 2018). In total, 296 premature infants were enrolled and compared with a control group of 66 healthy term infants from a 2011 study, immunized according to the same schedule with the same vaccines.

EXPOSURES

Three primary doses of the diphtheria-tetanus toxoids-acellular pertussis-inactivated poliomyelitis-Haemophilus influenza type b-hepatitis B combination vaccine were given at 2, 3, and 4 months after birth followed by a booster at 11 months and a 10-valent pneumococcal conjugate vaccine at 2, 4, and 11 months after birth.

MAIN OUTCOMES AND MEASURES

Primary end points were (1) proportion of preterm infants who achieved IgG antibody against vaccine antigens at concentrations above the internationally defined threshold for protection after the primary series and booster dose and (2) serum IgG geometric mean concentrations after the primary series and booster vaccination. Proportions and geometric mean concentrations were compared in preterm infants and the control group of term infants.

RESULTS

Of 296 preterm infants (56.1% male; mean gestational age, 30 weeks), complete samples before vaccination, 1 month after the primary series, and 1 month after the booster were obtained from 220 preterm infants (74.3%). After the primary series, the proportion of preterm infants across all gestational age groups who achieved protective IgG antibody levels against pertussis toxin, diphtheria, tetanus and 6 of 10 pneumococcal serotypes varied between 83.0% and 100%, Haemophilus influenzae type b between 34.7% and 46.2% (40.6% among all preterm infants overall), and pneumococcal serotypes 4, 6B, 18C, and 23F between 45.8% and 75.1%. After the booster dose, protective antibody levels were achieved in more than 95% of all preterm groups, except for Haemophilus influenzae type b (88.1%). In general, geometric mean concentrations of all vaccine-induced antibodies were significantly lower in all preterm infants vs term infants, except for pertussis toxin and pneumococcal serotypes 4 and 19F after the primary series and booster vaccination.

CONCLUSIONS AND RELEVANCE

Among preterm infants, administration of routine vaccinations during the first year of life was associated with protective antibody levels against most antigens in the majority of infants after the primary series and booster, except for Haemophilus influenzae type b. However, antibody concentrations were generally lower among preterm infants compared with historical controls.