Current antenatal pertussis vaccination guidelines miss preterm infants: An epidemiological study from the Northern Territory

Optimising the timing of whooping cough immunisation in mums (OpTIMUM) through investigating pertussis vaccination in pregnancy: an open-label, equivalence, randomised controlled trial

BACKGROUND

Pertussis vaccination in pregnancy is recommended in many countries to provide protection to young infants. The best timing for this vaccination is uncertain. In the UK, vaccination is recommended between 16 weeks and 32 weeks of gestation. In this trial we aimed to investigate the equivalence of three time periods for pertussis vaccination in pregnancy.

METHODS

In this open-label, equivalence, randomised controlled trial to investigate equivalence of different time windows for pertussis vaccination in pregnancy, participants were randomly assigned (1:1:1 ratio) to receive a pertussis-containing vaccine (Boostrix-inactivated poliovirus vaccine) in one of three gestational age groups, comprising group 1 (≤23 weeks + 6 days), group 2 (24-27 weeks + 6 days), and group 3 (28-31 weeks + 6 days) using a computer-generated randomisation list. The primary outcome was concentration of pertussis-specific antibodies in the infant born at term at birth. Maternal blood sampling was done before and 2 weeks after vaccination and at delivery, together with a cord sample, and an infant sample was collected at least 4 weeks after primary vaccination. Reactogenicity was assessed for 7 days after vaccination. This trial was registered with ClinicalTrials.gov (NCT03908164).

FINDINGS

Between May 7, 2019, and Feb 13, 2020, of 1010 women assessed for eligibility, 364 women were recruited and 351 received the intervention (120 in group 1, 119 in group 2, and 112 in group 3). Equivalence of time periods was demonstrated for anti-pertussis toxin and anti-pertactin IgG concentrations. The cord blood geometric mean concentrations of anti-filamentous haemagglutinin IgG were higher with increasing gestational age at vaccination, such that for infants in group 1 (≤23 weeks + 6 days), equivalence to group 3 (28-31 weeks + 6 days) was not shown. Reported rates of fever were similar between study groups.

INTERPRETATION

Pertussis vaccination at three different time intervals in pregnancy resulted in equivalent concentrations of IgG antibodies in infants against two of the three pertussis antigens assessed. Overall, these findings support recommendations to vaccinate any time between 16 weeks and 32 weeks of gestation.

FUNDING

The Thrasher Research Fund and the National Immunisation Schedule Evaluation Consortium through the National Institute for Health and Care Research policy research programme.

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.

Impact of extending the timing of maternal pertussis vaccination on hospitalized infant pertussis in England, 2014 - 2018

BACKGROUND

In October 2012 a maternal pertussis vaccination program was introduced in England for women between 28 and 32 weeks of pregnancy. In April 2016, the recommended optimal window was extended to 20-32 weeks to improve vaccine coverage and protect preterm infants.This study assesses the impact of offering maternal pertussis vaccination earlier in pregnancy on hospitalized infant pertussis cases.

METHODS

Hospitalized pertussis cases ≤60 days old in England were extracted from Hospital Episode Statistics pre-policy change and post policy change. Data were linked to laboratory-confirmed cases and clinical records were reviewed where cases were not matched. Maternal vaccine status of identified cases was established. Median hospital duration was calculated, and a competing risk survival analysis undertaken to assess multiple factors.

RESULTS

A total of 201 cases were included in the analysis. Of the 151 cases with reported gestational age, the number of hospitalizations amongst full-term infants was 60 cases pre-policy and 62 cases post policy, respectively while preterm cases declined from 20 to 9 (p=0.06). Length of hospital stay did not differ significantly after the policy change. Significantly longer hospital stays were seen in cases aged 0- 4 weeks (median of 3 more days than infants 5-8 weeks), premature infants (median of 4 more days than term infants) and cases with coinfections (median of 1 more day than those without coinfection).

CONCLUSIONS

The number of preterm infants hospitalized with pertussis in England halved after the policy change and preterm infants were no longer over-represented amongst hospitalized cases.

Effectiveness of strategies to increase uptake of pertussis vaccination by new parents and family caregivers: A systematic review

OBJECTIVES

Cocoon immunisation strategies involve administration of Bordetella pertussis containing vaccines to parents and family members who are in close contact with newborns. The objective of this systematic review was to evaluate the effectiveness of strategies to increase uptake of vaccination against Bordetella pertussis infection by parents and family caregivers of newborn children (< 3 months of age).

DESIGN

A protocol driven systematic review was conducted between 2005 and February 2020. CINAHL, Medline, and Google Scholar databases were searched.

SETTING

Inpatient maternity care units, ante-natal and post-natal clinics based in acute care or primary/community care contexts.

PARTICIPANTS

(i) mothers, (ii) fathers and (iii) family caregivers or other regular household contacts of infants < 3 months of age.

INTERVENTIONS

Health promotion interventions and immunisation clinics designed to promote "cocoon immunisation" against Bordetella pertussis infections of the newborn.

MEASUREMENTS

Change in uptake of adult vaccination with a pertussis containing vaccine (dTpa or Tdap) by new parents and family caregivers.

FINDINGS

Eight studies were included in this review. Strategies used to promote vaccination included: written and verbal education, promotional videos, provision of vaccine prescriptions and financial incentives, opportunistic vaccination of family members and population-based health promotional messaging. Six of the eight studies reported positive impacts on vaccination uptake. Four studies evaluating providing opportunistic immunisation during the obstetric admission reported statistically significant increases in maternal (+39% to +57%), paternal (+21% to +52%) and household members (+32%) vaccination rates. Targeted public health campaigns were also found to increase vaccination uptake but in isolation were insufficient to achieve vaccination of all household contacts.

CONCLUSION

Promotion of pertussis vaccination to new parents and the provision of opportunistic vaccination during the obstetric admission or post-natal visit, was the most successful strategy to increase uptake of pertussis vaccination by family caregivers.