The protective role of maternally derived antibodies against Bordetella pertussis in young infants

Interventional study to improve pertussis and influenza vaccination uptake in pregnant women

OBJECTIVES

Pertussis and influenza are endemic infections and associated with relevant morbidity and mortality in newborns and young infants. The Swiss Federal Office of Public Health has recommended influenza vaccination since 2011 and pertussis vaccination in pregnancy (ViP) since 2013 and expanded to repetition in each pregnancy since 2017. ViP is safe and effective in preventing severe diseases, but implementation is a challenge. We hypothesized that the proportion of women receiving ViP is persistently low despite existing national recommendations. Our primary objective was to compare the proportion of pertussis and influenza vaccine recommendations for and its acceptance by pregnant women before and after an information campaign tailored to obstetricians. Secondly, we aimed to identify reasons for missing or declining ViP.

STUDY DESIGN

We conducted a prospective, single-center, single-arm implementation study in the maternity ward at the University Women's Hospital Basel. We performed standardized interviews with women hospitalized for postpartum care before (October to December 2019, Phase 1, n = 262) and after an information campaign (October to December 2020, Phase 2, n = 233) and compared categorical variables using chi-squared or Fisher's exact test and continuous variables using Whitney Mann U test.

RESULTS

We found no significant differences in the proportion of recommendation for pertussis ViP (80 % vs. 84 %, p = 0.25) and implementation (76 % vs. 78 %, p = 0.63) between Phase 1 and 2. Main reasons for missing or declining vaccinations were lack of recommendation (62.8 %) and safety concerns regarding the unborn child (17.7 %). In contrast, the proportion of recommendation for influenza ViP (45 % vs. 63 %, p < 0.001) and implementation (29 % vs. 43 %, p < 0.001) increased significantly.

CONCLUSION

Proactive recommendations by obstetricians play a key role in the implementation of ViP but is still insufficient in our setting. We believe that future efforts should aim to explore possible hurdles that impede recommendations by obstetricians for ViP. The focus should be on the needs and experiences of obstetricians in private practice, but also other health care professionals involved in care of pregnant women. Local campaigns do not seem effective enough, therefore national campaigns with new strategies are desirable.

[Should French pregnant women be vaccinated against pertussis during pregnancy?]

Many countries with a high perinatal level have started a policy of vaccination of pregnant women against pertussis. To date, France has not chosen this policy. The objective was to review knowledge on pertussis mortality in infants. Compare the strategies available to protect the infant before his first vaccination, scheduled for two months of age. We proceeded to a litterature analysis, from January 1998 to 2021. Search by the following keywords used ; "Whooping cough, vaccination, pregnancy, strategy, cocooning", on the scientific basis of "Pubmed", as well as French and foreign vaccination recommendations. Currently 90% of whooping cough deaths are concerning infants under six months of age and this mortality represents 2% of mortality in the first year of life. Vaccination at birth is not effective. The cocooning strategy, which consists of vaccinating those around the child, is expensive and difficult to implement. A systematic vaccination policy for pregnant women is effective and reasonably expensive when compared to the cocooning strategy. In England, it was recently accompanied by a 78% reduction in confirmed cases of pertussis in infants under six months of age. In conclusion, compared to cocooning strategy, pertussis vaccination of pregnant women appears more effective and cost-effective, and this with each pregnancy.

Infant antibody levels following 10-valent pneumococcal-protein D conjugate and DTaP-Hib vaccinations in the first year of life after maternal Tdap vaccination: An open-label, parallel, randomised controlled trial

BACKGROUND

Maternal antibody levels after Tdap vaccination during pregnancy may affect infant primary antibody responses to pertussis, Tetanus toxoid (TT), Diphtheria toxoid (DT) vaccinations and pneumococcal vaccines with diphtheria toxin mutants like CRM197 as carrier protein.

METHODS

Mothers were recruited in an open label randomised parallel controlled trial in 2014-2016 through midwifes. They received Tdap [Boostrix] at 30-32 weeks of pregnancy (n = 58) or within 48 h after delivery (n = 60). Infants received DTaP-IPV-Hib-HepB [Infanrix Hexa] and 10-valent protein D conjugated pneumococcal conjugate vaccine (PHiD-CV10 [Synflorix]) at age 3, 5 and 11 months. We now report on infant specific IgG levels towards DT, TT, Haemophilus influenzae type b polyribosylribitol phosphate (Hib PRP) and PHiD-CV10 before and after primary- and booster vaccination as secondary study endpoints; pertussis antibodies were the primary endpoint of the study. This trial is registered in clinicaltrialsregister.eu (EudraCT 2012-004006-9) and trialregister.nl (NTR number NTR4314).

FINDINGS

Post primary vaccinations, antibody levels to DT, but not TT, were significantly lower after Tdap vaccination during pregnancy compared to controls (GMC ratio 0.4, 95% CI 0.3-0.6 and 0.9, 95% CI 0.6-1.2, respectively). Antibodies to serotype 19F were significantly lower in the maternal Tdap group, whereas there were no differences in antibody levels to Hib PRP and the other 9 pneumococcal serotypes. Post booster vaccinations, no significant differences were observed, except for DT.

INTERPRETATION

Maternal Tdap vaccination results in significant interference with infants responses not only to DT but also to conjugated pneumococcal vaccines containing DT mutants as carrier proteins. These interactions after maternal Tdap vaccination need to be taken into account when designing infants' national immunization schedules and choice of vaccines.

FUNDING

The Dutch Ministry of Health, Welfare and Sport.

Association between the timing of maternal vaccination and newborns' anti-pertussis toxin antibody levels

BACKGROUND

Pertussis remains an important global public health concern, despite the presence of extensive immunization programs. Incidence and severity of pertussis are typically higher in neonates and young infants. As a strategy to protect these young infants, maternal vaccination with Tdap (tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis) has been recommended in Brazil. The objective of this study was to evaluate the effects of Tdap vaccination during pregnancy on the anti-pertussis toxin (PT) IgG response in mothers and their infants at birth.

MATERIAL AND METHODS

Maternal and cord blood samples were collected from vaccinated (n = 243) and unvaccinated (n = 75) pregnant women, at the time of delivery, from July 2015 to August 2016 in São Paulo, Brazil. Anti-PT IgG antibodies were quantified by Enzyme-Linked Immunosorbent Assay (ELISA) and geometric mean concentrations (GMC) were calculated. Relationship between timing of vaccination and antibody concentrations were evaluated.

RESULTS

Maternal and cord blood GMCs among the vaccinated group were 5.4 and 5.6 fold higher [66.5 International Units (IU)/mL and 89.8 IU/mL] compared to the unvaccinated group (12.4 IU/mL and 16.1 IU/mL), respectively (p < 0.001). Higher anti-PT IgG GMCs were observed when vaccination occurred ≥60 days before delivery compared to <60 days, suggesting that vaccination early in the third trimester may be more effective than later in pregnancy.

CONCLUSION

Tdap maternal vaccination results in significantly higher anti-PT IgG in newborn infants and supports the current recommendation of the Brazilian Immunization Program.

Child-parent immunization survey: How well are national immunization recommendations accepted by the target groups?

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Most of the time gynecologists had not recommended vaccinations to pregnant women.

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Only 3% of mothers were vaccinated against pertussis and influenza in pregnancy.

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Misconceptions led to non-compliance of pregnant women with recommended vaccinations.

Background

Pertussis disease rates are high in Switzerland, especially in infants and young infants. To protect newborns from this serious disease, EKIF, the Swiss National Immunization Technical Advisory Group, has recommended vaccination against pertussis during pregnancy (2nd or 3rd trimester) since 2013. Also, since 2009, EKIF has recommended vaccination against influenza during pregnancy.

We conducted this study to assess acceptance and implementation of these recently introduced recommendations.

Methods

We performed standardized interviews with parents of children born on or after 01.01.2013, hospitalized at the University of Basel Children’s Hospital, Switzerland, between January and June 2017. If participation was declined, partial consent was sought for four questions regarding age, education level, attitudes towards vaccinations in general and availability of vaccination records.

Results

In 193 of 398 eligible children the mother participated. Five (3%) of 172 mothers had received both pertussis and influenza vaccines during pregnancy, 15 (9%) only against pertussis and 12 (7%) only against influenza. Very few mothers had received vaccination recommendation during pregnancy: 17 (10%) for both pertussis and influenza and 15 (9%) each for pertussis and influenza only. Main reasons for refusal of vaccination despite recommendation were that they were not deemed useful (59% for influenza and 37% for pertussis) and safety concerns for the child (18% for influenza and 26% for pertussis).

Conclusions

Recommendation for and immunization rates against pertussis and influenza during pregnancy are low and need to be improved. As recommendations from health care personnel have been shown to have the most significant impact on immunization rates, we propose to focus on improving awareness and acceptance for immunization in pregnancy among health care personnel involved in the care of pregnant women.

Antenatal vaccination to decrease pertussis in infants: safety, effectiveness, timing, and implementation

Pertussis remains a serious global health issue in infants aged less than 6 months. Neonates and young infants have the highest risk of developing pertussis as they are too young to be vaccinated and thus are more likely to develop more severe pertussis-related complications, including death. Protecting this vulnerable age population from pertussis is considered a main priority in many national health programs. Two vaccine strategies exist to protect infants from pertussis: "cocooning" and maternal vaccination during pregnancy. The latter is the more recent and preferred strategy, which protects newborns by passive transplacental transfer of pertussis antibodies. We review the reported evidence on the safety, effectiveness, timing and implementation of this antenatal immunization strategy.

Pertussis seroepidemiology in women and their infants in Sarlahi District, Nepal

Background

Infants are at greatest risk for pertussis morbidity and mortality. Maternal vaccination during pregnancy has been shown to prevent pertussis in young infants in high- and middle-income countries. However, data on the levels of maternal pertussis antibodies and the efficiency of transplacental transfer in low-income South Asian settings are limited.

Objective

To estimate the prevalence of maternal pertussis antibodies and the efficiency of transplacental transfer in rural southern Nepal.

Design/methods

Paired maternal-infant blood samples were collected from a subsample of participants in a randomized, controlled trial of maternal influenza immunization (n = 291 pairs). Sera were tested by enzyme-linked immunosorbent assays for pertussis toxin, filamentous hemagglutinin, pertactin, and fimbriae. Maternal and infant pertussis antibody levels and transplacental transfer efficiency were determined and potential factors associated with both were assessed.

Results

Elevated maternal antibodies to pertussis toxin, suggesting recent pertussis infection, were rarely detected (4%, tested n = 305). However, paired maternal-cord sera were highly correlated across all antibodies; transplacental antibody transfer ratios for pertussis toxin were 1.14 (n = 291, 95% CI 1.07–1.20); filamentous hemagglutinin 1.10 (n = 120, 95% CI: 1.01–1.20); fimbriae 2/3 1.05 (n = 120, 95% CI: 0.96–1.15) and pertactin 0.96 (n = 289, 95% CI: 0.91–1.00). Older gestational age was associated with increased pertussis toxin and decreased fimbriae 2/3 antibody transport.

Conclusions

A low prevalence of maternal antibody to all four pertussis antigens was noted in Nepal, but transplacental antibody transfer was efficient. No consistent demographic factors were associated with elevated maternal antibody levels or efficiency of transplacental transfer. If an increase in infant pertussis disease burden was detected in this population, maternal immunization could be an effective intervention to prevent disease in early infancy.

Bordetella pertussis

Pertussis is a highly infectious vaccine-preventable cough illness that continues to be a significant source of morbidity and mortality around the world. The majority of human illness is caused by Bordetella pertussis, and some is caused by Bordetella parapertussis. Bordetella is a Gram-negative, pleomorphic, aerobic coccobacillus. In the past several years, even countries with high immunization rates in early childhood have experienced rises in pertussis cases. Reasons for the resurgence of reported pertussis may include molecular changes in the organism and increased awareness and diagnostic capabilities, as well as lessened vaccine efficacy and waning immunity. The most morbidity and mortality with pertussis infection is seen in infants too young to benefit from immunization. Severe infection requiring hospitalization, including in an intensive care setting, is mostly seen in those under 3 months of age. As a result, research and public health actions have been aimed at better understanding and reducing the spread of Bordetella pertussis. Studies comparing the cost benefit of cocooning strategies versus immunization of pregnant women have been favorable towards immunizing pregnant women. This strategy is expected to prevent a larger number of pertussis cases, hospitalizations, and deaths in infants <1 year old while also being cost-effective. Studies have demonstrated that the source of infection in infants usually is a family member. Efforts to immunize children and adults, in particular pregnant women, need to remain strong.

Influence of maternal vaccination against diphtheria, tetanus, and pertussis on the avidity of infant antibody responses to a pertussis containing vaccine in Belgium

Maternal antibodies induced by vaccination during pregnancy cross the placental barrier and can close the susceptibility gap to pertussis in young infants up to the start of primary immunization. As not only the quantity but also the quality of circulating antibodies is important for protection, we assessed whether maternal immunization affects the avidity of infant vaccine-induced IgG antibodies, in the frame of a prospective clinical trial on pregnancy vaccination in Belgium. Infants born from Tdap (Boostrix®) vaccinated (N = 55) and unvaccinated (N = 26) mothers were immunized with a hexavalent pertussis containing vaccine (Infanrix Hexa®) at 8, 12 and 16 weeks, followed by a fourth dose at 15 months of age. Right before and one month after this fourth vaccine dose, the avidity of IgG antibodies against diphtheria toxin (DT), tetanus toxin (TT), pertussis toxin (PT), filamentous hemagglutinin (FHA) and pertactin (Prn) was determined using 1.5 M ammonium thiocyanate as dissociating agent. In both groups, antibody avidity was moderate for TT, PT, FHA and Prn and low for DT after priming. After a fourth dose, antibody avidity increased significantly to high avidity for TT and PT, whereas it remained moderate for FHA and Prn and low for DT. The avidity correlated positively with antibody level in both study groups, yet not significantly for PT. When comparing both study groups, only PT-specific antibodies showed significantly lower avidity in infants born from vaccinated than from unvaccinated mothers after the fourth vaccine dose. The clinical significance of lower avidity of vaccine induced infant antibodies after maternal vaccination, if any, needs further investigation.

The Effect of Maternal Pertussis Immunization on Infant Vaccine Responses to a Booster Pertussis-Containing Vaccine in Vietnam

BACKGROUND

 Maternal vaccination with an acellular pertussis (aP)-containing vaccine is a recommended strategy in a growing number of industrialized countries, to protect young infants from disease. Little is known on the effect of this strategy in low- and middle-income countries. Following a previous report on the effect of adding a pertussis and diphtheria component to the tetanus vaccination program in pregnant women in Vietnam, we report on infant immune responses to a booster aP vaccine dose in this randomized controlled clinical trial.

METHODS

 Thirty infants of Tdap (tetanus, diphtheria, and acellular pertussis)-vaccinated pregnant women and 37 infants of women vaccinated with a tetanus-only vaccine received a fourth aP-containing vaccine dose in the second year of life. Blood was taken 1 month after the fourth infant dose. Immunoglobulin G (IgG) antibodies against pertussis toxin (PT), filamentous hemagglutinin (FHA), pertactin (Prn), tetanus toxoid (TT), and diphtheria toxoid (DT) were measured using commercially available enzyme-linked immunosorbent assays (ELISA).

RESULTS

 One month after the booster dose, significantly lower antibody titers were measured in the Tdap group for anti-TT IgG (P < .001) only. Anti-DT IgG, anti-PT IgG, anti-Prn IgG, and anti-FHA IgG antibody titers were comparable for both groups. A rise in antibody concentrations was elicited for all (except DT) antigens after boosting.

CONCLUSIONS

 The present results indicate that the blunting of infant pertussis responses induced by maternal immunization, measured after a primary series of aP vaccines, was resolved with the booster aP vaccine dose. These results add to the evidence for national and international decision makers on maternal immunization as a vaccination strategy for protection of young infants against infectious diseases.

The optimal gestation for pertussis vaccination during pregnancy: a prospective cohort study

BACKGROUND

There is an increasing incidence of pertussis infection in infants too young to be adequately protected via vaccination. Maternal pertussis vaccination during the third trimester of pregnancy is a new strategy to provide protection to newborn infants.

OBJECTIVE

This study sought to determine the optimal gestational window for vaccination in the third trimester.

STUDY DESIGN

This prospective study recruited 3 groups of women: an early vaccination group, vaccinated between 28-32 weeks' gestation; a late vaccination group, vaccinated between 33-36 weeks' gestation; and an unvaccinated control group. Maternal venous blood was taken prior to pertussis vaccination. At birth, infant cord blood was collected to determine antibody levels to pertussis toxin (PT), pertactin (PRN), and filamentous hemagglutinin (FHA).

RESULTS

In all, 154 women were recruited from April through September 2014. There was no significant difference between maternal PRN and FHA antibody levels among the 3 groups, however, PT was higher in the early compared to late vaccination group (P = .05). Cord blood antibody levels to PT, PRN, and FHA were significantly higher in those born to vaccinated women compared with unvaccinated controls (P < .001, P = .001, and P < .001, respectively). Vaccination between 28-32 weeks' gestation resulted in significantly higher cord blood PT (4.18.0 vs 3.50 IU/mL, P = .009), PRN (5.83 vs 5.31 IU/mL, P = .03), and FHA (5.56 vs 5.03 IU/mL, P = .03) antibody levels than vaccination between 33-36 weeks' gestation. When adjusted for maternal prevaccination antibody levels, PT levels in early vs late vaccination approached significance (P = .06). PRN levels were significantly higher in the early vaccination group (P = .003). There was no significant difference for FHA antibody levels between the 2 groups (P = .16).

CONCLUSION

Maternal vaccination during the third trimester is effective in affording higher levels of pertussis antibody protection to the newborn infant. Vaccination early in the third trimester appears more effective than later in pregnancy.

Burden and Outcomes of Severe Pertussis Infection in Critically Ill Infants

OBJECTIVES

Despite World Health Organization endorsed immunization schedules, Bordetella pertussis continues to cause severe infections, predominantly in infants. There is a lack of data on the frequency and outcome of severe pertussis infections in infants requiring ICU admission. We aimed to describe admission rates, severity, mortality, and costs of pertussis infections in critically ill infants.

DESIGN

Binational observational multicenter study.

SETTING

Ten PICUs and 19 general ICUs in Australia and New Zealand contributing to the Australian and New Zealand Paediatric Intensive Care Registry.

PATIENTS

Infants below 1 year of age, requiring intensive care due to pertussis infection in Australia and New Zealand between 2002 and 2014.

MEASUREMENTS AND MAIN RESULTS

During the study period, 416 of 42,958 (1.0%) infants admitted to the ICU were diagnosed with pertussis. The estimated population-based ICU admission rate due to pertussis ranged from 2.1/100,000 infants to 18.6/100,000 infants. Admission rates were the highest among infants less than 60 days old (p < 0.0001). Two hundred six infants (49.5%) required mechanical ventilation, including 20 (4.8%) treated with high-frequency oscillatory ventilation, 16 (3.8%) with inhaled nitric oxide, and 7 (1.7%) with extracorporeal membrane oxygenation. Twenty of the 416 children (4.8%) died. The need for mechanical ventilation, high-frequency oscillatory ventilation, nitric oxide, and extracorporeal membrane oxygenation were significantly associated with mortality (p < 0.01). Direct severe pertussis-related hospitalization costs were in excess of USD$1,000,000 per year.

CONCLUSIONS

Pertussis continues to cause significant morbidity and mortality in infants, in particular during the first months of life. Improved strategies are required to reduce the significant healthcare costs and disease burden of this vaccine-preventable disease.

Rediscovering Pertussis

Pertussis, caused by Bordetella (B.) pertussis, a Gram-negative bacterium, is a highly contagious airway infection. Especially in infants, pertussis remains a major health concern. Acute infection with B. pertussis can cause severe illness characterized by severe respiratory failure, pulmonary hypertension, leucocytosis, and death. Over the past years, rising incidence rates of intensive care treatment in young infants were described. Due to several virulence factors (pertussis toxin, tracheal cytotoxin, adenylate cyclase toxin, filamentous hemagglutinin, and lipooligosaccharide) that promote bacterial adhesion and invasion, B. pertussis creates a unique niche for colonization within the human respiratory tract. The resulting long-term infection is mainly caused by the ability of B. pertussis to interfere with the host's innate and adaptive immune system. Although pertussis is a vaccine-preventable disease, it has persisted in vaccinated populations. Epidemiological data reported a worldwide increase in pertussis incidence among children during the past years. Either acellular pertussis (aP) vaccines or whole-cell vaccines are worldwide used. Recent studies did not detect any differences according to pertussis incidence when comparing the different vaccines used. Most of the currently used aP vaccines protect against acute infections for a period of 6-8 years. The resurgence of pertussis may be due to the lack of herd immunity caused by missing booster immunizations among adolescents and adults, low vaccine coverages in some geographic areas, and genetic changes of different B. pertussis strains. Due to the rising incidence of pertussis, probable solution strategies are discussed. Cocooning strategies (vaccination of close contact persons) and immunizations during pregnancy appear to be an approach to reduce neonatal contagiousness. During the past years, studies focused on the pathway of the immune modulation done by B. pertussis to provide a basis for the identification of new therapeutic targets to enhance the host's immune response and to probably modulate certain virulence factors.

Pertussis vaccination during pregnancy in Belgium: Follow-up of infants until 1 month after the fourth infant pertussis vaccination at 15 months of age

Vaccination of pregnant women with a pertussis containing vaccine is a recommended strategy in some industrialized countries, to protect young infants from severe disease. One of the effects of the presence of high titers of passively acquired maternal antibodies in young infants is blunting of immune responses to infant vaccination. We present infant immune responses to a fourth pertussis containing vaccine dose at 15 months of age, as a follow-up of previously presented data. In a prospective cohort study, women were either vaccinated with an acellular pertussis vaccine (Boostrix(®)) during pregnancy (vaccine group) or received no vaccine (control group). All infants were vaccinated with Infanrix Hexa(®) according to the standard Belgian vaccination schedule (8/12/16 weeks, 15 months). We report results from blood samples collected before and 1 month after the fourth vaccine dose. Immunoglobulin G (IgG) antibodies against pertussis toxin (PT), filamentous hemagglutinin (FHA), pertactin (Prn), tetanus toxoid (TT) and diphtheria toxoid (DT) were measured using commercially available ELISA tests. Antibody levels were expressed in International Units per milliliter. Demographic characteristics were similar in the vaccine and control group. Before the fourth vaccine dose, significantly lower antibody titers were measured in the vaccine group compared to the control group for anti-Prn IgG (p=0.003) and anti-DT IgG (p=0.023), with a steep decay of antibody titers since post-primary vaccination. One month after the fourth dose, antibody titers were only significantly lower in the vaccine group for anti-PT IgG (p=0.006). For all antigens, there was a rise in antibody titer after the fourth vaccine dose. The present results indicate still a minor blunting effect 1 month after a fourth vaccine dose for anti-PT antibodies. However, a good humoral immune response on all measured antigens was elicited in both groups of children. The clinical significance of such blunting effect is yet unknown. Clinicaltrials.gov identifier: NCT01698346.

Maternal Immunization Earlier in Pregnancy Maximizes Antibody Transfer and Expected Infant Seropositivity Against Pertussis

Guidelines recommend that pregnant women be vaccinated against pertussis between gestational weeks 26 and 36. We show that this narrow window can be widened, as optimal neonatal antibody concentrations and expected infant seropositivity rates are elicited between weeks 13 and 33.

Background. Maternal immunization against pertussis is currently recommended after the 26th gestational week (GW). Data on the optimal timing of maternal immunization are inconsistent.

Methods. We conducted a prospective observational noninferiority study comparing the influence of second-trimester (GW 13–25) vs third-trimester (≥GW 26) tetanus-diphtheria-acellular pertussis (Tdap) immunization in pregnant women who delivered at term. Geometric mean concentrations (GMCs) of cord blood antibodies to recombinant pertussis toxin (PT) and filamentous hemagglutinin (FHA) were assessed by enzyme-linked immunosorbent assay. The primary endpoint were GMCs and expected infant seropositivity rates, defined by birth anti-PT >30 enzyme-linked immunosorbent assay units (EU)/mL to confer seropositivity until 3 months of age.

Results. We included 335 women (mean age, 31.0 ± 5.1 years; mean gestational age, 39.3 ± 1.3 GW) previously immunized with Tdap in the second (n = 122) or third (n = 213) trimester. Anti-PT and anti-FHA GMCs were higher following second- vs third-trimester immunization (PT: 57.1 EU/mL [95% confidence interval {CI}, 47.8–68.2] vs 31.1 EU/mL [95% CI, 25.7–37.7], P < .001; FHA: 284.4 EU/mL [95% CI, 241.3–335.2] vs 140.2 EU/mL [95% CI, 115.3–170.3], P < .001). The adjusted GMC ratios after second- vs third-trimester immunization differed significantly (PT: 1.9 [95% CI, 1.4–2.5]; FHA: 2.2 [95% CI, 1.7–3.0], P < .001). Expected infant seropositivity rates reached 80% vs 55% following second- vs third-trimester immunization (adjusted odds ratio, 3.7 [95% CI, 2.1–6.5], P < .001).

Conclusions. Early second-trimester maternal Tdap immunization significantly increased neonatal antibodies. Recommending immunization from the second trimester onward would widen the immunization opportunity window and could improve seroprotection.

Reciprocal interference of maternal and infant immunization in protection against pertussis

BACKGROUND

Because of the current re-emergence of pertussis, vaccination during the 3rd trimester of pregnancy is recommended in several countries in order to protect neonates by placental transfer of maternal antibodies. Here, we examined the potential reciprocal interference of mother and infant vaccination in protection against pertussis in mice.

METHODS

Female mice were vaccinated with acellular pertussis vaccines and protection against Bordetella pertussis challenge, as well as functional antibodies were measured in their offspring with or without re-vaccination.

RESULTS

Maternal immunization protected the offspring against B. pertussis challenge, but protection waned quickly and was lost after vaccination of the infant mice with the same vaccine. Without affecting antibody titers, infant vaccination reduced the protective functions of maternally-derived antibodies, evidenced both in vitro and in vivo. Protection induced by infant vaccination was also affected by maternal antibodies. However, when mothers and infants were immunized with two different vaccines, no interference of infant vaccination on the protective effects of maternal antibodies was noted.

CONCLUSION

It may be important to determine the functionality of antibodies to evaluate potential interference of maternal and infant vaccination in protection against pertussis.

Continued high incidence of children with severe influenza A(H1N1)pdm09 admitted to paediatric intensive care units in Germany during the first three post-pandemic influenza seasons, 2010/11-2012/13

BACKGROUND

Previous influenza surveillance at paediatric intensive care units (PICUs) in Germany indicated increased incidence of PICU admissions for the pandemic influenza subtype A(H1N1)pdm09. We investigated incidence and clinical characteristics of influenza in children admitted to PICUs during the first three post-pandemic influenza seasons, using active screening.

METHODS

We conducted a prospective surveillance study in 24 PICUs in Bavaria (Germany) from October 2010 to September 2013. Influenza cases among children between 1 month and 16 years of age admitted to these PICUs with acute respiratory infection were confirmed by PCR analysis of respiratory secretions.

RESULTS

A total of 24/7/20 influenza-associated PICU admissions were recorded in the post-pandemic seasons 1/2/3; incidence estimates per 100,000 children were 1.72/0.76/1.80, respectively. Of all 51 patients, 80% had influenza A, including 65% with A(H1N1)pdm09. Influenza A(H1N1)pdm09 was almost absent in season 2 (incidence 0.11), but dominated PICU admissions in seasons 1 (incidence 1.35) and 3 (incidence 1.17). Clinical data was available for 47 influenza patients; median age was 4.8 years (IQR 1.6-11.0). The most frequent diagnoses were influenza-associated pneumonia (62%), bronchitis/bronchiolitis (32%), secondary bacterial pneumonia (26 %), and ARDS (21%). Thirty-six patients (77 %) had underlying medical conditions. Median duration of PICU stay was 3 days (IQR 1-11). Forty-seven per cent of patients received mechanical ventilation, and one patient (2%) extracorporeal membrane oxygenation; 19% were treated with oseltamivir. Five children (11%) had pulmonary sequelae. Five children (11%) died; all had underlying chronic conditions and were infected with A(H1N1)pdm09. In season 3, patients with A(H1N1)pdm09 were younger than in season 1 (p = 0.020), were diagnosed more often with bronchitis/bronchiolitis (p = 0.004), and were admitted to a PICU later after the onset of influenza symptoms (p = 0.041).

CONCLUSIONS

Active screening showed a continued high incidence of A(H1N1)pdm09-associated PICU admissions in the post-pandemic seasons 1 and 3, and indicated possible underestimation of incidence in previous German studies. The age shift of severe A(H1N1)pdm09 towards younger children may be explained by increasing immunity in the older paediatric population. The high proportion of patients with underlying chronic conditions indicates the importance of consistent implementation of the current influenza vaccination recommendations for risk groups in Germany.

Pertussis vaccination during pregnancy in Belgium: Results of a prospective controlled cohort study

Vaccination during pregnancy has been recommended in some countries as a means to protect young infants from severe infection. Nevertheless, many aspects are still unknown and possible blunting of the infant's immune responses by maternal antibodies, is one of the concerns with maternal vaccination. We report the first prospective controlled cohort study in women and infants on the effects of using Boostrix(®), a combined tetanus, diphtheria and acellular pertussis vaccine, during pregnancy. The primary aim was to measure the influence of this booster dose on the titer and duration of the presence of maternal antibodies in the infants and assess possible interference with infant immune responses. In a controlled cohort study, 57 pregnant women were vaccinated with Tdap vaccine (Tetanus Diphtheria acellular Pertussis, Boostrix, GSK Biologicals), at a mean gestational age of 28.6 weeks. A control group of pregnant women (N=42) received no vaccine. Antibody geometric mean concentrations (GMCs) against tetanus (TT), diphtheria (DT), pertussis toxin (PT), filamentous haemagglutinin (FHA) and pertactin (Prn) were measured with commercial ELISA tests in samples taken preceding maternal vaccination and one month afterwards, at delivery and from the cord blood, and in infants before and 1 month after the primary series of 3 pertussis containing hexavalent vaccines. Infants born to vaccinated women had significantly higher GMC at birth and during the first 2 months of life for all vaccine antigens compared to the offspring of unvaccinated women, thereby closing the susceptibility gap for pertussis in infants. However, blunting was noticed for infant diphtheria and pertussis toxin vaccine responses (p<0.001) in the infants from vaccinated women after the primary vaccination schedule (weeks 8,12 and 16). Since pertussis vaccination has been recommended during pregnancy already, the results of this study support that recommendation and provide additional scientific evidence to document possible interference by maternal antibodies.

The Decline of Pertussis-Specific Antibodies After Tetanus, Diphtheria, and Acellular Pertussis Immunization in Late Pregnancy

We prospectively measured pertussis-specific antibodies 9-15 months after delivery in women immunized with tetanus, diphtheria, and acellular pertussis (Tdap) after the 20th week of their recent pregnancy. The Tdap-immunized women (n = 38) exhibited a decline in geometric mean concentrations between their peripartum and follow-up levels for immunoglobulin G to pertussis toxin (21.48 [95% confidence interval, 12.51-36.89] vs 11.72 [7.09-19.37] IU/mL];); filamentous hemagglutinin (185.95 [157.93-218.94] vs 140.33 IU/mL [113.46-173.57] IU/mL); and pertactin (171.52 [120.73-243.67] vs 83.74 [60.58-115.75] IU/mL) (all P < .001). For women immunized with Tdap during late pregnancy, pertussis-specific immunoglobulin G levels decreased significantly 9-15 months after delivery.

Strategies to decrease pertussis transmission to infants

The Global Pertussis Initiative (GPI) is an expert scientific forum addressing the worldwide burden of pertussis, which remains a serious health issue, especially in infants. This age cohort is at risk for developing pertussis by transmission from those in close proximity. Risk is increased in infants aged 0 to 6 weeks, as they are too young to be vaccinated. Older infants are at risk when their vaccination schedules are incomplete. Infants also bear the greatest disease burden owing to their high risk for pertussis-related complications and death; therefore, protecting them is a high priority. Two vaccine strategies have been proposed to protect infants. The first involves vaccinating pregnant women, which directly protects through the passive transfer of pertussis antibodies. The second strategy, cocooning, involves vaccinating parents, caregivers, and other close contacts, which indirectly protects infants from transmission by preventing disease in those in close proximity. The goal of this review was to present and discuss evidence on these 2 strategies. Based on available data, the GPI recommends vaccination during pregnancy as the primary strategy, given its efficacy, safety, and logistic advantages over a cocoon approach. If vaccination during pregnancy is not feasible, then all individuals having close contact with infants <6 months old should be immunized consistent with local health authority guidelines. These efforts are anticipated to minimize pertussis transmission to vulnerable infants, although real-world effectiveness data are limited. Countries should educate lay and medical communities on pertussis and introduce robust surveillance practices while implementing these protective strategies.

Protecting newborns against pertussis: the value of vaccinating during pregnancy

Resurgence of pertussis has recently been reported in several countries with long-standing pertussis immunization and high vaccination coverage. This situation requires consideration of alternative immunization strategies to protect newborns. In the absence of a vaccine that confers long-lasting immunity, maternal vaccination for pertussis during pregnancy seems to be a safe, immunogenic, effective and accepted strategy to protect infants during the first weeks of life. The existing scientific evidence provides the grounds for pregnant women and healthcare workers to make informed decisions regarding this measure as well as for countries with high pertussis-related infant morbidity and mortality that should consider implementation. Furthermore, this could be a promising strategy to address other vaccine-preventable diseases of pregnancy and the neonatal period.

Pandemic influenza A vs seasonal influenza A in hospitalized children in Athens

BACKGROUND

Data on pandemic H1N1 influenza (pH1N1) virus infection in hospitalised children are limited.

AIMS AND OBJECTIVES

To examine the epidemiological and clinical characteristics of children hospitalised with pH1N1 at a large tertiary-care centre in Athens and compare them with those of children hospitalised with seasonal influenza A in previous years.

METHODS

All children (n = 146) admitted with confirmed pH1N1 between October 2009 to February 2010 and January 2011 to May 2011 were included. Data on children ≧ 6 months of age (n = 109) were compared with those of 138 children admitted with seasonal influenza A who were examined during two previous influenza seasons (2002-2003 and 2004-2005).

RESULTS

The age distribution was similar between seasonal and pandemic H1N1. Bronchial asthma was significantly more common in the seasonal influenza group but the clinical presentation was similar in the two groups, except that fever was more common in patients with pH1N1. Children admitted with seasonal influenza were more likely to develop acute otitis media. There were no significant differences between the two groups for severe outcomes (admission to the ICU, mechanical ventilation or death). Only one child with seasonal influenza (0.6%) and three with pH1N1 influenza (2%) required admission to the ICU. Mean length of hospitalisation was longer in the seasonal influenza group.

CONCLUSION

Clinical manifestations were similar between pH1N1 and seasonal influenza, and the pandemic virus did not appear to cause more severe disease in hospitalised children.

Management and prevention of pertussis infection in neonates

Despite the fact that universal immunization against pertussis led to a dramatic decrease in the incidence and mortality in high-income countries, it has left a window of vulnerability for newborns. Although specific guidelines concerning management of neonatal whooping cough have not yet been developed, the present review summarizes the main available recommendations on diagnostic work-up and treatment of neonatal pertussis. Additionally, new prevention strategies are explored, including the use of an additional booster dose of vaccine to adolescents and adults, vaccination of healthcare workers, immunization of household contacts and caregivers (cocooning strategy), vaccination of pregnant women and, finally, neonatal immunization with novel vaccines. These strategies are analyzed and discussed in terms of efficacy, safety and cost-effectiveness.

Pertussis: still a cause of death, seven decades into vaccination

PURPOSE OF REVIEW

We review the resurgence of pertussis, including recent trends in epidemiology and reasons for the resurgence, as well as updated vaccination schedules and recommendations.

RECENT FINDINGS

There has been a resurgence of pertussis in recent decades, in the United States and worldwide. This is a preventable cause of hospitalizations and deaths, especially among the infant population. Possible reasons for the resurgence include increased awareness via surveillance and reporting, diagnostic testing improvements, infant susceptibility coupled with exposure to infected caregivers, waning immunity despite complete vaccination, inferior long-term efficacy of acellular vaccines compared with whole-cell vaccines, circulating mutant strains of the bacterium, and parents refusing vaccination of their children. Progressively updated vaccine recommendations should be adhered to, as this is currently the only available tool to stem the public health challenge.

SUMMARY

The resurgence of pertussis is a multifaceted problem, but the implementation of immunization for all age groups is of utmost importance.

The effect of timing of maternal tetanus, diphtheria, and acellular pertussis (Tdap) immunization during pregnancy on newborn pertussis antibody levels - a prospective study

BACKGROUND

The Centers for Disease Control and Prevention recommend Tdap immunization during pregnancy, preferably at 27-36 weeks.

AIM

To ascertain whether there is a preferential period of maternal Tdap immunization during pregnancy that provides the highest concentration of pertussis-specific antibodies to the newborn.

METHODS

This prospective study measured pertussis-specific antibodies in paired maternal-cord sera of women immunized with Tdap after the 20th week of their pregnancy (n=61).

RESULTS

The geometric mean concentrations (GMCs) of Immunoglobulin G (IgG) to pertussis toxin (PT) were higher in the newborns' cord sera when women were immunized at 27-30(+6) weeks (n=21) compared with 31-36 weeks (n=30) and >36 weeks (n=7), 46.04 international units/milliliter (IU/mL) (95% CI, 24.29-87.30) vs. 8.69IU/mL (95% CI, 3.66-20.63) and 21.12IU/mL (95% CI, 7.93-56.22), p<0.02, respectively. The umbilical cord GMCs of IgG to filamentous hemagglutinin (FHA) were higher in the newborns' cord sera when women were immunized at 27-30(+6) weeks compared with 31-36 weeks and >36 weeks, 225.86IU/mL (95% CI, 182.34-279.76) vs. 178.31IU/mL (95% CI, 134.59-237.03) and 138.03IU/mL (95% CI, 97.61-195.16), p<0.02, respectively.

CONCLUSIONS

Immunization of pregnant women with Tdap between 27-30(+6) weeks was associated with the highest umbilical cord GMCs of IgG to PT and FHA compared with immunization beyond 31 weeks gestation. Further research should be conducted to reaffirm these finding in order to promote an optimal pertussis controlling policy.

Protecting newborns from pertussis - the challenge of complete cocooning

BACKGROUND

An increase of pertussis cases, especially in young infants and adolescents, has been noted in various countries. Whooping cough is most serious in neonates and young infants in whom it may cause serious complications such as cyanosis, apnoea, pneumonia, encephalopathy and death. To protect newborns and infants too young to be fully immunized, immunization of close contact persons has been proposed ("cocoon strategy") and implemented in several countries, including Switzerland in 2011. The goal of this study was to assess knowledge about pertussis among parents of newborns and acceptance, practicability and implementation of the recently recommended pertussis cocoon strategy in Switzerland.

METHODS

We performed a cross sectional survey among all parents of newborns born between May and September 2012 and 2013 in Basel city and country. Regional statistical offices provided family addresses after approval by the ethical and data protection committees. A standardized questionnaire with detailed instructions was sent to all eligible families. For statistical analyses, independent proportions were compared by Pearson's chi-squared test.

RESULTS

Of 3546 eligible parents, 884 (25%) participated. All three questions exploring pertussis knowledge were answered correctly by 37% of parents; 25% gave two correct answers, 22% gave one correct answer and in the remaining 16% no answer was correct. Pertussis immunization as part of cocooning was recommended to 20% and 37% of mothers and 14% and 32% of fathers in the 2012 and 2013 study cohorts, respectively. Principal advisors for cocooning were pediatricians (66%) followed by gynecologists/obstetricians (12%) and general practitioners (5%). When recommended, 64% of mothers and 59% of fathers accepted pertussis immunization. The majority of vaccinations were administered in the perinatal period and within 2 months of the child's birth. However, cocooning remained incomplete in 93% of families and in most families <50% of close contacts received pertussis vaccination.

CONCLUSIONS

Implementation of cocooning for protecting newborns from pertussis is challenging and usually remains incomplete. Pertussis immunization rates among close contacts of newborns need to be improved. Ideally, all healthcare providers involved in family planning, pregnancy and child birth should recommend cocooning. Pertussis immunization of pregnant women is an additional measure for optimal protection of newborns and should be promoted.

Safety and immunogenicity of tetanus diphtheria and acellular pertussis (Tdap) immunization during pregnancy in mothers and infants: a randomized clinical trial

IMPORTANCE

Maternal immunization with tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine could prevent infant pertussis.

OBJECTIVE

To evaluate the safety and immunogenicity of Tdap immunization during pregnancy and its effect on infant responses to diphtheria and tetanus toxoids and acellular pertussis (DTaP) vaccine.

DESIGN, SETTING, AND PARTICIPANTS

Phase 1-2, randomized, double-blind, placebo-controlled, clinical trial conducted from 2008 to 2012. Forty-eight pregnant women aged 18 to 45 years received Tdap (n = 33) or placebo (n = 15) at 30 to 32 weeks' gestation, with crossover immunization postpartum.

INTERVENTIONS

Tdap vaccination at 30 to 32 weeks' gestation or postpartum.

MAIN OUTCOMES AND MEASURES

Primary outcomes were maternal and infant adverse events, pertussis illness, and infant growth and development until age 13 months. Secondary outcomes were antibody concentrations in pregnant women before and 4 weeks after Tdap immunization or placebo, at delivery and 2 months' postpartum, and in infants at birth, at 2 months, and after the third and fourth doses of DTaP.

RESULTS

No Tdap-associated serious adverse events occurred in women or infants. Injection site reactions after Tdap immunization were reported in 26 (78.8% [95% CI, 61.1%-91.0%]) and 12 (80% [95% CI, 51.9%-95.7%]) pregnant and postpartum women, respectively (P > .99). Systemic symptoms were reported in 12 (36.4% [ 95% CI, 20.4%-54.9%]) and 11 (73.3% [95% CI, 44.9%-92.2%]) pregnant and postpartum women, respectively (P = .03). Growth and development were similar in both infant groups. No cases of pertussis occurred. Significantly higher concentrations of pertussis antibodies were measured at delivery in women who received Tdap during pregnancy vs postpartum (eg, pertussis toxin antibodies: 51.0 EU/mL [95% CI, 37.1-70.1] and 9.1 EU/mL [95% CI, 4.6-17.8], respectively; P < .001) and in their infants at birth (68.8 EU/mL [95% CI, 52.1-90.8] and 14.0 EU/mL [95% CI, 7.3-26.9], respectively; P < .001) and at age 2 months (20.6 EU/mL [95% CI, 14.4-29.6] and 5.3 EU/mL [95% CI, 3.0-9.4], respectively; P < .001). Antibody responses in infants born to women receiving Tdap during pregnancy were not different following the fourth dose of DTaP.

CONCLUSIONS AND RELEVANCE

This preliminary assessment did not find an increased risk of adverse events among women who received Tdap vaccine during pregnancy or their infants. For secondary outcomes, maternal immunization with Tdap resulted in high concentrations of pertussis antibodies in infants during the first 2 months of life and did not substantially alter infant responses to DTaP. Further research is needed to provide definitive evidence of the safety and efficacy of Tdap immunization during pregnancy.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00707148.

Prospective nationwide surveillance of hospitalizations due to pertussis in children, 2006-2010

BACKGROUND

Frequency of pertussis is highly variable from country to country and it depends on multiple factors including case definitions and type of surveillance systems used. Many countries recently reported an increase of pertussis cases especially in infants and adolescents.

METHODS

From April 2006 to March 2011, 15-year-old patients hospitalized with suspected or proven pertussis were reported to the Swiss Pediatric Surveillance Unit. Patients with ≥14 days of cough plus paroxysms, whooping or post-tussive vomiting fulfilled the clinical case definition of pertussis. For laboratory confirmation, Bordetella pertussis polymerase chain reaction was offered free of charge.

RESULTS

Data were available from 159 of 173 reported cases and 130 (90% of them <12 months old) were eligible including 125 laboratory-confirmed B. pertussis infections. Rates per 100,000 population were 2.6 (<16 years) and 38.8 (<12 months), respectively. Most frequent complications were cyanosis (63%) and sleep disturbance (60%); 35 (27%) patients received intensive care and 1 patient died. Source of infection was known in 79 (61%) patients and was mainly a sibling, parent or both. Most patients were unimmunized (65%) or incompletely immunized (30%).

CONCLUSIONS

The high rate of pertussis hospitalization in young infants established in this surveillance project and the incomplete pertussis immunization status in almost all hospitalized patients require further efforts for improvement. In addition, introduction of pertussis immunizations for all adolescents (in 2013), young adults (in 2012) and pregnant women (in 2013) in Switzerland should increase indirect protection of vulnerable newborns and infants too young to be fully immunized.

The pertussis problem

Pertussis is resurgent, and many cases are occurring in vaccinated children and adolescents. In countries using acellular vaccines, waning immunity is at least part of the problem. This article discusses possible improvements in those vaccines.

Immune responses in infants whose mothers received Tdap vaccine during pregnancy

BACKGROUND

The effect of maternal Tdap vaccination on infant immunologic responses to routine pediatric vaccines is unknown.

METHODS

This was a cohort study of infants whose mothers received or did not receive Tdap vaccine during pregnancy. Maternal and cord blood samples were collected at delivery; infant blood samples were collected before and after primary series and booster dose of diphtheria, tetanus, and acellular pertussis (DTaP) and other vaccines. Geometric mean antibody concentrations or titers to pertussis, hepatitis B, tetanus, diphtheria, Haemophilus influenzae type b and polio antigens were measured. Mean maternal-to-cord blood antibody ratios were calculated.

RESULTS

At delivery, maternal and cord antibody concentrations to pertussis antigens were higher in the Tdap group (n=16) than control group (n=54; maternal: 1.9- to 20.4-fold greater; cord: 2.7- to 35.5-fold greater). Increased antibody concentrations persisted for infants at first DTaP (3.2- to 22.8-fold greater). After primary series, antibody concentrations to pertussis antigens were lower in Tdap group (0.7- to 0.8-fold lower), except for fimbriae types 2 and 3 (FIM) (1.5-fold greater). Antibody concentrations to pertussis antigens before and after booster dose were comparable (prebooster: Tdap group 1.0- to 1.2-fold higher than controls; postbooster: 0.9- to 1.0-fold lower). Differences in FIM values at these time points are difficult to interpret, due to varying FIM content among DTaP vaccines administered to infants in both groups.

CONCLUSIONS

Maternal Tdap immunization resulted in higher pertussis antibody concentrations during the period between birth and the first vaccine dose. Although slightly decreased immune responses following the primary series were seen compared with controls, differences did not persist following the booster.