Maternal immunization: an update for pediatricians

Impact of maternal SARS-CoV-2 booster vaccination on blood and breastmilk antibodies

Maternal COVID-19 vaccination could protect infants who are ineligible for vaccine through antibody transfer during pregnancy and lactation. We measured the quantity and durability of SARS-CoV-2 antibodies in human milk and infant blood before and after maternal booster vaccination. Prospective cohort of lactating women immunized with primary and booster COVID-19 vaccines during pregnancy or lactation and their infants. Milk and blood samples from October 2021 to April 2022 were included. Anti-nucleoprotein (NP) and anti-receptor binding domain (RBD) IgG and IgA in maternal milk and maternal and infant blood were measured and compared longitudinally after maternal booster vaccine. Forty-five lactating women and their infants provided samples. 58% of women were anti-NP negative and 42% were positive on their first blood sample prior to booster vaccine. Anti-RBD IgG and IgA in milk remained significantly increased through 120-170 days after booster vaccine and did not differ by maternal NP status. Anti-RBD IgG and IgA did not increase in infant blood after maternal booster. Of infants born to women vaccinated in pregnancy, 74% still had positive serum anti-RBD IgG measured on average 5 months after delivery. Infant to maternal IgG ratio was highest for infants exposed to maternal primary vaccine during the second trimester compared to third trimester (0.85 versus 0.29; p<0.001). Maternal COVID-19 primary and booster vaccine resulted in robust and long-lasting transplacental and milk antibodies. These antibodies may provide important protection against SARS-CoV-2 during the first six months of life.

Pertussis antibody levels in infants and their mothers receiving combined tetanus-diphtheria toxoid and acellular pertussis vaccine during pregnancy in Turkey

OBJECTIVE

Pertussis is an important cause of morbidity and mortality in infants under two months of age and these high risk babies are dependent on maternally derived antibodies until completion of their first immunization series. This study aimed to evaluate the vaccine response of late preterm and term newborns as well as their mothers who underwent combined tetanus-diphtheria toxoid and acellular pertussis (Tdap) vaccination during pregnancy.

STUDY DESIGN

A total of 70 pregnant women were administered Tdap vaccine (Boostrix®, GSK) between 27 and 33 gestational weeks of pregnancy. The IgG antibodies against pertussis toxin (PT) and filamentous hemagglutinin (FHA) in maternal blood before vaccination and in both maternal and umbilical cord blood after vaccination were evaluated using the in-house ELISA method. The geometric mean concentrations (GMC) and placental transfer ratios of antibodies were measured.

RESULTS

Participants' with a mean age of 29.59 ± 4.70 years received Tdap vaccine at an average 28.6 ± 1.31 gestational weeks. Average pre and post vaccination levels of anti-PT IgG GMCs and anti-FHA IgG GMCs were 8.01 IU/ml vs 39.48 IU/ml (p = 0.001) and 122.24 IU/ml vs 183.97 IU/ml (p < 0.001), respectively. The anti-PT and anti-FHA IgG GMCs of cord blood after vaccination was 25.15 IU/ml and 118.77 IU/ml, respectively (p < 0.001 and p = 0.064). Placental transfer ratios of anti-PT ve anti-FHA IgG antibodies were detected as 0.65 and 0.62, respectively.

CONCLUSION

Immunization of pregnant women with Tdap at the third trimester results in high maternal and infant antibody levels. Maternal immunization during each pregnancy seems to be the best strategy in revealing the highest maternal and infant antibodies and in narrowing the gap between birth and immune system maturation in infants. Pregnant women in our country should also get the Tdap vaccine during pregnancy especially in the early third trimester.

Preterm birth: Case definition & guidelines for data collection, analysis, and presentation of immunisation safety data

Preterm birth is commonly defined as any birth before 37 weeks completed weeks of gestation. An estimated 15 million infants are born preterm globally, disproportionately affecting low and middle income countries (LMIC). It contributes directly to estimated one million neonatal deaths annually and is a significant contributor to childhood morbidity. However, in many clinical settings, the information available to calculate completed weeks of gestation varies widely. Accurate dating of the last menstrual period (LMP), as well as access to clinical and ultrasonographic evaluation are important components of gestational age assessment antenatally. This case definition assign levels of confidence to categorisation of births as preterm, utilising assessment modalities which may be available across different settings. These are designed to enable systematic safety evaluation of vaccine clinical trials and post-implementation programmes of immunisations in pregnancy.

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.

Bordetella pertussis seroprevalence in Belgian adults aged 20-39 years, 2012

SUMMARY The last report on pertussis seroprevalence in Belgium concerned samples collected during 1993-1994. In the context of the Eupert-Labnet WP6 seroprevalence study (comparing sera from 16 European member states), 1500 anonymized leftover diagnostic samples were collected randomly during the second semester of 2012 by the clinical chemistry laboratories of six participating Belgian centres, distributed equally between Flanders, Wallonia and Brussels Capital Region. As suggested by the WP6 organizers, a total of 750 samples (125/centre) were selected from subjects in the 20-29 years age group and 750 samples (125/centre) from subjects in the 30-39 years age group. Anti-PT IgG levels were measured using Virion-Serion ELISA and analysed using predefined cut-off levels. Sixty-one (4%) sera were indicative of an infection in the past 2 years (between 50 and 100 IU/ml) and another 61 (4%) sera had anti-PT IgG antibodies reflecting acute infection (>100 IU/ml). These results highlight the presence of a Bordetella pertussis reservoir in the adult 'healthy' Belgian population.