Enhanced surveillance of tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccines in pregnancy in the Vaccine Adverse Event Reporting System (VAERS), 2011-2015

Safety and Clinical Benefits of Adacel® and Adacel®-Polio Vaccination in Pregnancy: A Structured Literature Review

Vaccination in pregnancy using a tetanus toxoid, reduced dose diphtheria toxoid, and reduced dose acellular pertussis (Tdap) vaccine is important for prevention of severe pertussis disease in young infants. The objectives of this systematic literature review were to search for original research studies evaluating the vaccine effectiveness, immunogenicity, and safety of Adacel®/Adacel-Polio® used during pregnancy to prevent pertussis disease in young infants. Medical databases used included EMBASE, BIOSIS Previews, and Chemical Abstracts, with search terms related to pregnancy, vaccines/immunization, safety, pertussis, effectiveness/efficacy, and immune response; other potentially eligible reports were included where applicable. Search results were restricted to literature published from 1 January 1995 to 26 July 2021. A total of 2021 articles and 4 other reports were identified for primary review. A total of 49 publications qualified for inclusion after primary and secondary reviews. Effectiveness studies of Adacel or Adacel-Polio given in pregnancy consistently showed high levels of protection from pertussis disease in the newborn (vaccine effectiveness: 91-93%). In immunogenicity studies, the response in pregnant women was consistent with that of non-pregnant women. Infants of mothers vaccinated with Adacel or Adacel-Polio in pregnancy had higher anti-pertussis antibody levels at birth and at 2 months of age compared to infants born to women vaccinated with comparator vaccines, placebo, or those not vaccinated during pregnancy. There was evidence of a slightly decreased response to primary pertussis vaccination in infants of mothers vaccinated with Adacel or Adacel-Polio, but this was not thought to be clinically significant. In safety studies, Adacel or Adacel-Polio vaccination was well tolerated by pregnant woman and not associated with pregnancy, postpartum, or neonatal complications. In conclusion, Adacel or Adacel-Polio vaccination in pregnancy is highly effective in protecting young infants from pertussis disease, with a favorable safety profile for both pregnant women and their infants.

A phase 2 randomized controlled dose-ranging trial of recombinant pertussis booster vaccines containing genetically inactivated pertussis toxin in pregnant women

INTRODUCTION

Despite a decrease in infections caused by Bordetella pertussis due to COVID-19 pandemic, booster vaccination of pregnant women is still recommended to protect newborns. Highly immunogenic vaccines containing genetically inactivated pertussis toxin (PTgen) and filamentous hemagglutinin (FHA) may generate comparable anti-PT antibody concentrations, even at lower doses, to chemically inactivated acellular pertussis vaccines (Tdapchem) shown effective for maternal immunization.

METHODS

This phase 2 randomized, observer-blind, active-controlled non-inferiority trial was conducted in healthy Thai pregnant women randomly assigned to receive one dose of low-dose recombinant pertussis-only vaccine containing 1 µg PTgen and 1 µg FHA (ap1gen), or tetanus, reduced-dose diphtheria combined with ap1gen (Tdap1gen), or combined with 2 µg PTgen and 5 µg FHA (Tdap2gen), or with 5 µg PTgen and 5 µg FHA (TdaP5gen, Boostagen®) or comparator containing 8 µg of chemically inactivated pertussis toxoid, 8 µg FHA, and 2.5 µg pertactin (Boostrix™, Tdap8chem). Blood was collected at Day 0 and Day 28 post-vaccination. The non-inferiority of the study vaccines was assessed based on anti-PT IgG antibody levels on Day 28 pooled with results from a similarly structured previous trial in non-pregnant women.

RESULTS

400 healthy pregnant women received one dose of vaccine. Combined with data from 250 non-pregnant women, all study vaccines containing PTgen were non-inferior to comparator vaccine (Tdap8chem). Both ap1gen and TdaP5gen vaccines could be considered to have superior immunogenicity to Tdap8chem. Local and systemic solicited reactions were similar among all vaccine groups.

CONCLUSIONS

Vaccine formulations containing PTgen were safe and immunogenic in pregnant women. The ap1gen vaccine, with the lowest cost and reactogenicity, may be suitable for use in pregnant women when diphtheria and tetanus toxoids are not needed. This study is registered in the Thai Clinical Trial Registry (www.

CLINICALTRIALS

in.th), number TCTR20180725004.

Impact of maternal whole-cell or acellular pertussis primary immunization on neonatal immune response

With the introduction of pertussis immunization for pregnant women in many countries, there has been renewed interest in the impact of whole-cell pertussis vaccine (wP) versus acellular vaccine (aP) on disease control, particularly regarding the best approach for priming. To gather evidence on this topic, we analyzed the impact of aP or wP priming on aP vaccination during pregnancy (aPpreg) in mice. Two-mother vaccination schemes were employed (wP-wP-aPpreg and aP-aP-aPpreg), and the immune response in the mothers and their offspring, as well as the protection of the offspring against Bordetella pertussis challenge, were assessed. Pertussis toxin (PTx)-specific IgG responses were detected in mothers after both the second and third doses, with higher titers after the third dose, regardless of the vaccination schedule. However, a significant reduction in PTx-IgG levels was observed after 22 weeks post aPpreg immunization in mothers with the aP-aP-aPpreg scheme but not in the wP-wP-aPpreg immunized mothers. The aP-aP-aPpreg schedule triggered a murine antibody response mainly to a Th2-profile, while wP-wP-aPpreg induced a Th1/Th2 mixed profile. Both immunization schemes administered to the mothers protected the offspring against pertussis, but the wP-wP-aPpreg vaccination conferred offspring protection in all pregnancies at least up to 20 weeks after receiving the aPpreg-dose. In contrast, the immunity induced by aP-aP-aPpreg began to decline in births that occurred 18 weeks after receiving the aPpreg dose. For the aP-aP-aPpreg scheme, pups born from gestations furthest from aPpreg (+22 weeks) had lower PTx-specific IgG levels than those born closer to the application of the dose during pregnancy. In contrast, for pups born to wP-wP-aPpreg vaccinated mothers, the PTx-specific IgG levels were maintained over time, even for those born at the longest time studied (+22 weeks). It is noteworthy that only the pups born from mothers with aP-aP-aPpreg and receiving a neonatal dose of either aP or wP were more susceptible to B. pertussis infection than mice with only maternal immunity, suggesting interference with the induced immunity (p<0.05). However, it should be noted that mice with maternal immunity, whether vaccinated or not with neonatal doses, are better protected against colonization with B. pertussis than mice without maternal immunity but vaccinated with aP or wP.

Spontaneous reports of primary ovarian insufficiency after vaccination: A review of the vaccine adverse event reporting system (VAERS)

BACKGROUND

Since 2012, reports of primary ovarian insufficiency (POI) temporally associated with receipt of human papillomavirus (HPV) vaccine have been published leading to questions about a potential causal association. A Vaccine Safety Datalink study did not find an increased risk for POI after vaccination. We reviewed the Vaccine Adverse Event Reporting System (VAERS) to describe POI reports.

METHODS

We searched VAERS, a U.S. passive surveillance system, for domestic POI reports received from 01/01/1990 to 12/31/2017 after any vaccination. The search used both Medical Dictionary for Regulatory Activity Preferred Terms and a text-based search for POI and its symptoms. All reports were reviewed, and the American College of Obstetricians and Gynecologists (ACOG) guidelines for POI diagnosis were applied. Data mining for disproportionate reporting was conducted.

RESULTS

Six hundred fifty-two reports met the search criteria and clinical review identified 19 POI reports. Most reports (n = 16) were received between 2013 and 2017. The median age at vaccination was 14.5 years (range 10-25 years) and the median interval between first dose of vaccination and reporting the event to VAERS was 43 months (range 4-132 months; mean 59.6 months). Four reports met ACOG diagnostic criteria; one with an underlying cause (47XXX chromosomal abnormality) reported. Eleven reports documented menstrual irregularity ≥ 3 months; 5 had ≥ 1 laboratory test result used to diagnose POI. Eighteen of 19 reports described receipt of HPV vaccine with or without other vaccines. Other vaccines reported were meningococcal conjugate vaccine, hepatitis A, varicella and tetanus toxoid, reduced diphtheria toxoid and acellular pertussis. Disproportionate reporting was found for three relevant coding terms after HPV vaccination.

CONCLUSIONS

POI is rarely reported to VAERS. Most reports contained limited diagnostic information and were submitted after published cases of POI following HPV vaccination. Results of our review do not suggest a safety concern.

[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.

Fourteen years of the Pregnancy Registry on maternal immunisation with a reduced-antigen-content tetanus-diphtheria-acellular pertussis (Tdap) vaccine

BACKGROUND

GSK initiated a Pregnancy Registry in the United States (US) for the reduced-antigen-content tetanus-diphtheria-acellular pertussis (Tdap; Boostrix, GSK) vaccine with the aim to detect and describe pregnancy outcomes in women vaccinated with Boostrix 28 days before estimated conception or during pregnancy.

METHODS

Voluntary reports of pregnancy exposure to Boostrix received from spontaneous and post-marketing surveillance sources in the US were assessed. Reports were classified as prospective or retrospective based on the knowledge of pregnancy outcomes at the time of reporting. For completeness, reports of exposure to Boostrix or to the Tdap-inactivated poliovirus vaccine (Boostrix-IPV, GSK) reported to the global safety database from countries outside the US were also evaluated.

RESULTS

From May 2005 to August 2019, 1517 (1455 prospective and 62 retrospective) pregnancy reports were received in the Boostrix US Pregnancy Registry. Of the prospective reports, 250 had known outcomes: 244 live infants with no apparent birth defects (BDs), three live infants with BDs, and three spontaneous abortions with no apparent BDs. Of the retrospective reports, 55 had known outcomes: 33 live infants with no apparent BDs, 16 live infants with BDs, one spontaneous abortion with no apparent BDs, four stillbirths with no apparent BDs, and one stillbirth with BDs. Cumulatively, 1321 pregnancy reports (1006 for Boostrix; 315 for Boostrix-IPV) were received from countries outside the US. Of these, 163 prospective reports and 551 retrospective reports had known outcomes. Results were in line with those from the Boostrix US Pregnancy Registry.

CONCLUSIONS

Data currently available from the Boostrix US Pregnancy Registry and from countries outside the US suggested that exposure to Boostrix or Boostrix-IPV during pregnancy does not raise safety concerns related to adverse pregnancy outcomes or BDs.

Safety and use of tetanus-diphtheria-acellular pertussis-5 (Tdap5) vaccine during pregnancy: findings from 11 years of reporting to a pregnancy registry

The "Adacel (Tdap5) Pregnancy Registry" was used to identify 1182 women who received the tetanus, diphtheria, acellular pertussis [5 components] (Tdap5) vaccine during pregnancy from 2005 to 2016. To evaluate the safety and use of prenatal Tdap5, we calculated the rate of maternal, obstetrical, pregnancy and neonatal outcomes following Tdap5 pregnancy exposure and assessed vaccine uptake by year and trimester of exposure. The most commonly reported maternal adverse events included injection site reactions (2.6%; 95% Confidence Interval 1.8%, 3.7%), nervous system events (1.3%; 0.8%, 2.1%) and musculoskeletal events (1.1%; 0.6%, 1.9%). The most commonly reported complications of pregnancy were hypertension/preeclampsia (5.5%; 3.3%, 8.9%) and gestational diabetes (2.5%; 1.1%, 5.3%), while those for labor and delivery were premature labor (2.9%; 1.4%, 5.7%) and premature membrane rupture (1.5%; 0.4%, 3.8%). These rates were similar to, or lower than those reported for the general population of pregnant women. Among pregnancies with known birth outcomes (N = 275), 90.4% (86.2%, 93.4%) resulted in a live birth, 5.9% (3.6%, 9.5%) in spontaneous abortion, 3.0% (1.4%, 5.8%) in stillbirth, and 0.7% (0.0%, 2.8%) in ectopic pregnancies. Most newborns had normal APGAR scores and birth weights (98.1% and 93.0%, respectively), and only two reported a congenital anomaly (0.7%; 0.0%, 2.8%). An influx of reports in 2012 with third trimester Tdap5 exposure coincided with the 2012 updated Advisory Committee on Immunization Practices recommendations. This analysis did not identify any safety concerns across the continuum of maternal, obstetrical, pregnancy, and neonatal outcomes in women who received Tdap5 vaccination during pregnancy.

Tetanus, Diphtheria, Acellular Pertussis Vaccination During Pregnancy and Risk of Pertussis in the Newborn in Publicly and Privately Insured Mother-infant Pairs in the United States

BACKGROUND

In the United States, pertussis circulation persists and primarily infects infants and children, despite routine vaccinations. To minimize infant morbidity and mortality from the disease before the first DTaP dose, the Advisory Committee on Immunization Practices recommends maternal Tdap vaccination in weeks 27-36 of pregnancy.

METHODS

Cohorts of mother-infant pairs in the Medicaid Analytic eXtract (MAX) (2010-2014) and IBM MarketScan (2011-2015) databases were analyzed to estimate the effectiveness of prenatal Tdap vaccination compared with no vaccination to prevent infant pertussis in the first 6 months. Hazard ratios were estimated with Cox proportional hazards models and adjusted for potential confounders via inverse probability weights. The impact of preterm delivery on the risk of pertussis was analyzed. Results from the 2 databases were pooled.

RESULTS

In MarketScan, women received Tdap vaccination before delivery in 114,067 (25.6%) of 445,638 pregnancies and in MAX, 33,286 (4.8%) of 695,262 pregnancies. Among pregnancies with preterm delivery, only 21.2% and 3.8% in MarketScan and MAX had been vaccinated. The risk of pertussis in unvaccinated term infants was 3.5 (MarketScan) and 17 (MAX) per 10,000; and in preterm infants, it was 8.4 (MarketScan) and 19.8 (MAX) per 10,000. The pooled hazard ratio for Tdap vaccination any time before delivery versus no vaccination was 0.64 [95% confidence interval (CI): 0.41-1.00]. The hazard ratio was 0.11 (95% CI: 0.03-0.36) for preterm and 0.78 (95% CI: 0.48-1.29) for term infants vaccinated before 37 weeks. The incidence of pertussis was higher and the protective hazard ratio stronger during pertussis outbreaks.

CONCLUSIONS

Prenatal Tdap vaccination reduces the risk of pertussis infections in the infants' first 6 months by 36%. Vaccination soon after 27 weeks of pregnancy, before when deliveries began, ensures vaccination includes those born preterm, who are at highest risk for pertussis and benefit particularly from this vaccination.

A phase IV, multi-centre, randomized clinical trial comparing two pertussis-containing vaccines in pregnant women in England and vaccine responses in their infants

BACKGROUND

Pertussis vaccines containing three or five pertussis antigens are recommended in pregnancy in many countries, but no studies have compared the effect on infants' antigen-specific immunoglobulin G (IgG) concentrations. The aim of this study was to compare anti-pertussis IgG responses following primary immunization in infants of mothers vaccinated with TdaP₅-IPV (low dose diphtheria toxoid, tetanus toxoid, acellular pertussis [five antigens] and inactivated polio) or TdaP₃-IPV in pregnancy (three pertussis antigens).

METHODS

This multi-centre phase IV randomized clinical trial was conducted in a tertiary referral centre and primary care sites in England. Women were randomized to receive TdaP₅-IPV (n = 77) or TdaP₃-IPV (n = 77) at 28-32 gestational weeks. A non-randomized control group of 44 women who had not received a pertussis-containing vaccine in pregnancy and their 47 infants were enrolled post-partum.

RESULTS

Following infant primary immunization, there was no difference in the geometric mean concentrations (GMCs) of anti-pertussis toxin, filamentous haemagglutinin or pertactin IgG between infants born to women vaccinated with TdaP₅-IPV (n = 67) or TdaP₃-IPV (n = 63). However, the GMC of anti-pertussis toxin IgG was lower in infants born to TdaP₅-IPV- and TdaP₃-IPV-vaccinated mothers compared to infants born to unvaccinated mothers (n = 45) (geometric mean ratio 0.71 [0.56-0.90] and 0.78 [0.61-0.98], respectively); by 13 months of age, this difference was no longer observed.

CONCLUSION

Blunting of anti-pertussis toxin IgG response following primary immunization occurs in infants born to women vaccinated with TdaP₅-IPV and TdaP₃-IPV, with no difference between maternal vaccines. The blunting effect had resolved by 13 months of age. These results may be helpful for countries considering which pertussis-containing vaccine to recommend for use in pregnancy.

TRIAL REGISTRATION

ClinicalTrials.gov , NCT02145624 , registered 23 May 2014.

Factors That Influence Infant Immunity and Vaccine Responses

The neonatal period and early infancy are times of increased vulnerability to infection. The immune system of infants undergoes rapid changes and a number of factors can influence the maturation and function of the early infant immune system, amongst these factors are maternal infections and immunity. Infants who are HIV-exposed, but uninfected show important immune alterations, which are likely to be associated with the increased morbidity and mortality observed in these infants. Maternally derived antibodies are crucial in early life to protect infants from infection during the time when their own immune system is becoming more experienced and fully mature. However, maternal antibodies can also interfere with the infant's own antibody responses to primary vaccination. Preterm infants are particularly vulnerable to infection, having not had the opportunity to benefit from the transplacental transfer of maternal antibodies in late pregnancy. In addition, further differences have been observed in the innate and adaptive immune system between preterm and term infants. Here, we focus on maternal influences on the infant immune system, using HIV and maternal vaccination as examples and finish by considering how prematurity impacts infant immune responses to vaccination.

The recombinant protein combined vaccine based on the fragment C of tetanus toxin and the cross-reacting material 197

Diphtheria and tetanus toxoids and acellular pertussis (DTaP) vaccines were widely used since 1940s. The exceptional success of childhood vaccination is undisputed. However, the anti-diphtheria and tetanus antibody will decrease with the increase of age in human body. A boosting vaccine for tetanus and diphtheria in adult is recommended by WHO. Recombinant protein vaccine has the advantages of single component and high safety, which is one of the directions to develop boosting vaccines. Therefore, in this study, we evaluated a recombinant TTc and CRM197 combination vaccine (RTCV) that uses the fragment C (TTc) of tetanus toxin and the cross-reacting material 197 (CRM197) of the diphtheria toxin mutant. Our results displayed that RTCV (composed of 10 μg/mL TTc, 20 μg/mL CRM197 antigens, and 500 μg/mL aluminum adjuvants) could induce high levels of IgG and IgG1 antibody in mice, which were similar as those induced by DTaP. These results will provide technical support for a novel boosting vaccine against diphtheria and tetanus. KEY POINTS: • We successfully expressed CRM197 protein in E. coli BL21 (DE3) using pET26b (+) vector. • The anti-TTc and anti-CRM197 antibody titer (IgG) of RTCV was similar with DTaP.

Reports of cell-based influenza vaccine administered during pregnancy in the Vaccine Adverse Event Reporting System (VAERS), 2013-2020

BACKGROUND

In November 2012, the first cell cultured influenza vaccine, a trivalent subunit inactivated influenza vaccine (Flucelvax(®), ccIIV3), was approved in the United States for adults aged ≥18 years. A quadrivalent version (ccIIV4) was later approved in 2016 and replaced ccIIV3. The safety of ccIIV3 or ccIIV4 (ccIIV) was not assessed for pregnant women or their infants during pre-licensure studies.

OBJECTIVE

To assess the safety of ccIIV administered during pregnancy in pregnant women and their infants whose reports were submitted to VAERS during 2013-2020.

MATERIAL AND METHODS

We searched VAERS for United States reports of adverse events (AEs) in pregnant women who received ccIIV from 1 July 2013 through 31 May 2020. Clinicians reviewed reports and available medical records and assigned a primary clinical category for each report. Reports were coded as serious based on the Code of Federal Regulations definition.

RESULTS

VAERS received 391 reports following ccIIV administered to pregnant women. Twenty-four (6.1%) were serious. Two neonatal deaths were reported. No maternal deaths occurred. Among reports with trimester information (n = 340), ccIIV was administered during the second trimester in 170 (50%). The most frequent pregnancy-specific AE was premature delivery in 85 (21.7%) reports, followed by dysmature placenta in 13 (3.3%) and pre-eclampsia/eclampsia in ten (2.3%). The most common non-pregnancy specific conditions were infectious conditions in 32 (8.2%). Among infant conditions, low birth weight was reported in 62 (15.9%) reports. Fifteen birth defects were reported; in 12 with gestational age information, administration of the vaccine occurred late in the second trimester or later.

CONCLUSIONS

Review of maternal ccIIV reports in VAERS was not unexpectedly different from other maternal influenza vaccine safety VAERS reviews.

Concomitant administration of a liquid formulation of human rotavirus vaccine (porcine circovirus-free) with routine childhood vaccines in infants in the United States: Results from a phase 3, randomized trial

BACKGROUND

In response to the detection of porcine circovirus type 1 (PCV-1) in the human rotavirus vaccine (HRV), a PCV-free HRV (no detection of PCV-1 and PCV-2 according to the detection limit of tests used) was developed. Liquid (Liq) PCV-free HRV previously showed immunogenicity and safety profiles comparable to lyophilized (Lyo) HRV.

METHODS

This was a phase 3a, randomized, single-blind study (NCT03207750) conducted in the United States. Healthy infants aged 6-12 weeks received 2 doses (0, 2 months) of either Liq PCV-free HRV or Lyo HRV with routine vaccines (0, 2, 4 months): diphtheria-tetanus-acellular pertussis, hepatitis B and inactivated poliovirus combination vaccine (DTaP-HBV-IPV), monovalent tetanus toxoid-conjugated vaccine against Haemophilus influenzae type b (Hib-TT), and 13-valent pneumococcal conjugate vaccine. Co-primary objectives were: (i) to assess non-inferiority of immune responses to routine vaccine antigens 1 month post-dose 3 following co-administration with Liq PCV-free HRV compared to Lyo HRV; (ii) to rule out a 10% decrease in seroresponse to pertussis antigens after dose 3. Other objectives were to evaluate immunogenicity and safety of HRV vaccines.

RESULTS

Of 1272 vaccinated infants, 990 (489 in Liq PCV-free HRV and 501 in Lyo HRV group) were included in the per-protocol set. All statistical criteria were met, thus co-primary objectives were demonstrated. Seroprotection/seropositivity rates in both groups were high: 100% for diphtheria/tetanus, ≥99.3% for HBV, ≥99.8% for polio, ≥99.8% for each pertussis antigen, ≥90.8% for all pneumococcal serotypes except serotype 3 (≥69.1%), and ≥ 97.4% for Hib. Most infants seroconverted for anti-RV antibodies (76.3% of Liq PCV-free HRV and 78.9% of Lyo HRV recipients). Geometric mean concentrations/titers were comparable between groups. Incidences of adverse events and serious adverse events were similar between groups.

CONCLUSION

Routine pediatric vaccines co-administered with Liq PCV-free HRV showed non-inferior immune responses and similar safety profiles to those following co-administration with Lyo HRV.

The Association of Prenatal Tetanus, Diphtheria, and Acellular Pertussis (Tdap) Vaccination With Attention-Deficit/Hyperactivity Disorder

As prenatal vaccinations become more prevalent, it is important to assess potential safety events. In a retrospective cohort study of Kaiser Permanente Southern California (Pasadena, California) mother-child pairs with birth dates during January 1, 2011-December 31, 2014, we investigated the association between prenatal tetanus, diphtheria, and acellular pertussis (Tdap) vaccination and risk of attention-deficit/hyperactivity disorder (ADHD) in offspring. Information on Tdap vaccination during pregnancy was obtained from electronic medical records. ADHD was defined by International Classification of Diseases codes (Ninth or Tenth Revision) and dispensed ADHD medication after age 3 years. Children were followed to the date of their first ADHD diagnosis, the end of Kaiser Permanente membership, or the end of follow-up (December 31, 2018). In Cox proportional hazards models, we estimated unadjusted and adjusted hazard ratios for the association between maternal Tdap vaccination and ADHD, with inverse probability of treatment weighting (IPTW) used to adjust for confounding. Of 128,756 eligible mother-child pairs, 85,607 were included in the final sample. The ADHD incidence rate was 3.41 per 1,000 person-years in the Tdap-vaccinated women and 3.93 per 1,000 person-years in the unvaccinated (hazard ratio = 1.01, 95% confidence interval: 0.88, 1.16). The IPTW-adjusted analyses showed no association between prenatal Tdap vaccination and ADHD in offspring (hazard ratio = 1.00, 95% confidence interval: 0.88, 1.14). In this study, prenatal Tdap vaccination was not associated with ADHD risk in offspring, supporting recommendations to vaccinate pregnant women.

Active SMS-based surveillance of adverse events following immunisation with influenza and pertussis-containing vaccines in Australian pregnant women using AusVaxSafety

BACKGROUND

Maternal immunisation is important to protect both mother and baby, but safety concerns can lead to low uptake. AusVaxSafety participant-based surveillance actively monitors adverse events following immunisation (AEFI) in Australia. We aimed to analyse AEFI in the days following vaccination with seasonal inactivated influenza vaccine (IIV) and/or reduced antigen diphtheria-tetanus-acellular pertussis vaccine (dTpa) in pregnant women in Australia.

METHODS

De-identified AEFI reports were solicited from vaccine recipients via automated SMS survey (using SmartVax software) following routine vaccination with IIV and/or dTpa at 219 national sentinel surveillance sites from 2015 to 2018. AEFI rates were compared by vaccine group (IIV alone, dTpa alone, or IIV and dTpa together), vaccine brand, trimester (IIV only) and vaccination period (April to August 2016-2018; IIV only). Women who had two vaccination encounters during surveillance were identified and AEFI rates compared for each dose.

RESULTS

Among 13,758 participants, overall AEFI rates were lower following IIV (4.9%) than dTpa (6.4%) or IIV and dTpa given concomitantly (7.4%). The AEFI profile was similar for both vaccines, with injection site reactions, tiredness, and headache most commonly reported. Injection site pain and swelling/redness were significantly more common in women who received dTpa than IIV. Reports of medical attendance following immunisation were similar (0.3%) for each vaccine group. AEFI rates did not differ by IIV brand (FluQuadri®, Fluarix® Tetra), dTpa brand (Boostrix®, Adacel®), or by trimester. Among women with sequential dTpa vaccinations, 6.0% (7/116) had an AEFI following their second dTpa dose.

CONCLUSIONS

Self-reported AEFI rates did not differ by trimester (IIV), or by vaccine brand (IIV or dTpa). Concomitant influenza and pertussis vaccination was associated with more frequent, but low rates of minor, expected AEFI. These real world 'citizen science-based' data provide further reassuring evidence of the safety of maternal vaccination.

Safety of Maternal Immunization Against Pertussis: A Systematic Review

The WHO recommends vaccination of all children against pertussis. However, newborn infants remain vulnerable to infection. Pertussis vaccination during pregnancy has been introduced in several countries to protect newborns via transplacental transfer of maternal pertussis antibodies to the infant. We reviewed the impact of maternal pertussis vaccination on the health of pregnant women, the developing fetus, and health of the newborn. We searched PubMed/MEDLINE, EMBASE, Scopus (Elsevier), Cochrane Database of Systematic Reviews, ProQuest, and Science Direct to identify studies that assessed the safety of maternal pertussis vaccination. Twenty-seven English language publications published between January 1995 and December 2018 were included in this review. Pregnant women receiving pertussis vaccines did not have increased rates of systemic or local reactions. There were no safety concerns with repeat vaccination with other tetanus-containing vaccines or their concomitant administration with influenza vaccines. Maternal pertussis vaccination did not adversely affect pregnancy, birth or neonatal outcomes. This review confirms the safety of maternal pertussis vaccination during pregnancy. FUNDING: Sanofi Pasteur. Plain language summary available for this article.

A Randomized Controlled Trial of the Safety and Immunogenicity of Tetanus, Diphtheria, and Acellular Pertussis Vaccine Immunization During Pregnancy and Subsequent Infant Immune Response

Background

Immunization of pregnant women with tetanus-diphtheria-acellular pertussis vaccine (Tdap) provides protection against pertussis to the newborn infant.

Methods

In a randomized, controlled, observer-blind, multicenter clinical trial, we measured the safety and immunogenicity of Tdap during pregnancy and the effect on the infant's immune response to primary vaccination at 2, 4, and 6 months and booster vaccination at 12 months of age. A total of 273 women received either Tdap or tetanus-diphtheria (Td) vaccine in the third trimester and provided information for the safety analysis and samples for the immunogenicity analyses; 261 infants provided serum for the immunogenicity analyses.

Results

Rates of adverse events were similar in both groups. Infants of Tdap recipients had cord blood levels that were 21% higher than maternal levels for pertussis toxoid (PT), 13% higher for filamentous hemagglutinin (FHA), 4% higher for pertactin (PRN), and 7% higher for fimbriae (FIM). These infants had significantly higher PT antibody levels at birth and at 2 months and significantly higher FHA, PRN, and FIM antibodies at birth and 2 and 4 months, but significantly lower PT and FHA antibody levels at 6 and 7 months and significantly lower PRN and FIM antibody levels at 7 months than infants whose mothers received Td. Differences persisted prebooster at 12 months for all antigens and postbooster 1 month later for PT, FHA, and FIM.

Conclusions

This study demonstrated that Tdap during pregnancy results in higher levels of antibodies early in infancy but lower levels after the primary vaccine series.

Clinical Trials Registration

NCT00553228.

Challenges in evaluating post-licensure vaccine safety: observations from the Centers for Disease Control and Prevention

Introduction: Vaccination is one of the most successful and cost-effective public health interventions. Although vaccines undergo extensive safety and efficacy evaluations prior to licensure, vaccine safety assessment post-licensure is essential for detecting rare and longer-term adverse events (AEs) and maintaining public confidence in vaccines and recommended immunization programs. Despite the proven effect of vaccines to save lives and prevent disease and overwhelming evidence of vaccines' safety and societal benefit, like any drug, no vaccine can be considered as completely safe and completely effective. New vaccines continue to be introduced and require rapid safety assessment post-licensure through pharmacovigilance reports as well as epidemiologic studies to investigate any potential safety signals.Areas covered: We discuss selected challenges for conducting pharmacovigilance and epidemiologic studies of AEs after vaccination in the United States using the post-licensure safety surveillance infrastructure of the Centers for Disease Control and Prevention (CDC).Expert opinion: The availability of specific post-licensure surveillance systems to monitor and study AEs after vaccination, such as the Vaccine Adverse Event Reporting System, the Vaccine Safety Datalink, and the Clinical Immunization Safety Assessment Project, each with its unique set of strengths and limitations, provide a harmonized and supportive approach to meet several of these barriers.

Insights and expectations for Tdap vaccination of pregnant women in Italy

BACKGROUND

Pertussis is a widespread vaccine-preventable disease, associated with an increasing trend to hospitalization among newborns. Pertussis in newborns can be fatal, and the most effective way to prevent it is maternal immunization (MI) with a reduced antigen content tetanus, diphtheria, and acellular pertussis vaccine (Tdap). In Italy, the National Immunization Plan (NIP) 2017-2019 introduced de novo Tdap vaccination during each pregnancy at no cost for the recipient. Despite this, vaccination coverage is suboptimal. This survey of pregnant women across Italy was conducted to investigate their knowledge and expectations of Tdap.

METHODS

A cross-sectional survey was conducted. Pregnant women up to 28th gestational weeks were interviewed by Telephone using a questionnaire with 16 questions. Statistics were descriptive.

RESULTS

The final sample recruited 600 respondents evenly distributed across Italy. The average duration of pregnancy at the time of the interview was 20.8 weeks (standard deviation [SD] 6.0). Most women (60.7%) were between 30 and 40 years of age. About half were aware of the risks of pertussis for newborns (54.5%) and the increased risk of hospitalization (59.8%); 47.2% were aware that Tdap MI was offered free of charge under the NIP. Safety information regarding the mother and newborn was considered the most important information in deciding whether to be vaccinated (47.4%), followed by safety information related only to the newborn (29.5%). About half (52.2%) stated that they would "certainly" accept MI, and 25.3% would like to receive more information. Gynecologists were the preferred healthcare providers (HCPs) for the provision of MI information (34.3%), followed by pediatricians (25.5%). Two-thirds of the respondents would prefer to be informed about MI before getting pregnant (66.0%). Vaccines investigated specifically for use in pregnancy were preferred by respondents. Overall, no relevant differences were observed between women pregnant for the first time and those with more than one pregnancy, nor between geographical regions.

CONCLUSIONS

The results show room for improving the awareness and understanding of the risks of pertussis for infants and the protective role of MI. The pregnant women preferred to receive advice on MI from an HCP, primarily their gynecologist. They were most interested in information on the safety profile of Tdap during pregnancy, on the mother, fetus, and newborn. The potential impact of this study to support clinical practice of Healthcare Providers is highlighted in the Focus on the Patient section. [Formula: see text].

The Effect of Maternal Immunisation During Pregnancy on Infant Vaccine Responses

INTRODUCTION

Immunisation during pregnancy to protect infants against tetanus, pertussis and influenza is recommended in many countries. However, maternal antibodies can interfere with infant vaccine responses. We investigated the effect of antenatal diphtheria-tetanus-acellular pertussis (dTpa) and trivalent inactivated influenza (TIV) immunisation on specific and heterologous antibody responses to routine immunisations given in the first year of life.

METHODS

In total, 471 healthy infants were included. At 7 and 13 months of age, antibodies to the primary course of routine vaccines given at 6 weeks, 4 and 6 months of age (pertussis (pertussis toxin (PT), filamentous haemagglutinin (FHA), pertactin (PRN)), polio (type 1, 2, 3), Haemophilus influenzae type b (Hib), pneumococcus (serotype 1, 3, 4, 5, 6A, 6B, 7F, 9V, 14, 18C, 19A, 19F, 23F)) were measured, and at 13 months of age, antibodies to the 12-month routine vaccines (Hib, meningococcus C, measles, mumps and rubella). The seroprotection rates for each vaccine and the geometric mean concentrations (GMC) of antibodies were compared between infants whose mothers did or did not receive dTpa or TIV immunisation during pregnancy.

RESULTS

A total of 369 infants were included in the final analysis. Maternal dTpa immunisation was associated with reduced antibody responses to both specific (diphtheria and pertussis) and heterologous (polio and pneumococcus) vaccine antigens. This effect was stronger for persistence of antibodies at 13 months of age than it was at 7 months of age. At 7 months of age, adjusted average antibody concentrations were significantly lower for diphtheria, pertussis (PT, FHA, PRN) and polio type 2, and at 13 months of age, for diphtheria, pertussis (PT, FHA, PRN), polio type 1-3 and pneumococcal serotypes 1, 4, 5, 6A, 6B, 7F, 18C and 23F. Additionally, at 13 months of age, seroprotection rates for diphtheria, PT, pneumococcal serotype 1, 6A and 6B were significantly lower in infants after maternal dTpa immunisation. In contrast, for Hib, in infants with maternal dTpa immunisation, the adjusted average antibody concentration and the seroprotection rate were higher, particularly at 7 months of age. Maternal TIV immunisation had minimal effect on infant vaccine responses.

CONCLUSION

Whilst maternal immunisation protects infants in the first few months of life, it might interfere with both specific and heterologous (unrelated) vaccines responses in infants.

RESEARCH IN CONTEXT

Evidence before this study: Maternal immunisation during pregnancy helps to protect infants during the period before they complete their primary immunisations. It has been proven to be safe and beneficial. However, pre-existing maternal antibodies can influence antibody responses following infant immunisation, an effect called 'blunting'. Previous studies have investigated the influence of dTpa but not influenza immunisation during pregnancy on infant vaccine responses. The majority of studies investigated antibody concentrations only to the specific vaccine antigens included in the maternal immunisation, and there is scarce data available on heterologous vaccine responses, particularly pneumococcal responses.Added value of this study: In this study, we have shown that maternal dTpa immunisation during pregnancy is associated with reduced antibody responses to both specific (diphtheria and pertussis) and heterologous (polio and pneumococcus) vaccine antigens. This effect is stronger for persistence of antibodies at 13 months of age than after primary immunisation at 7 months of age. In contrast, for Hib, in infants with maternal dTpa immunisation, antibody concentrations are higher, particularly at 7 months of age. Maternal TIV immunisation has minimal effect on infant vaccine responses.Implications of all the available evidence: Whilst maternal immunisation protects infants in the first few months of life, it might interfere with both specific and heterologous (unrelated) vaccines responses in infants. As most vaccines induce very high antibody responses, small differences in antibody concentrations may not be of clinical significance. However, since maternal immunisation during pregnancy also influences seroprotection rates, strategies, such as additional booster doses in the second year of life, particularly for pertussis and pneumococcus, might need to be considered to address this.

Is there any harm in administering extra-doses of vaccine to a person? Excess doses of vaccine reported to the Vaccine Adverse Event Reporting System (VAERS), 2007-2017

BACKGROUND

The administration of an extra dose of a vaccine may occur due to a programmatic error (e.g., vaccination error) when there is need to provide one of the antigens of a combination vaccine not readily available as a single antigen, or when there is need to provide immunization in a person with uncertain vaccination histories (e.g., refugees). There is little data available on the safety of an extra dose of vaccine.

OBJECTIVE

To assess for the presence of adverse events (AEs) most commonly reported following the administration of excess doses of vaccine in the Vaccine Adverse Event Reporting System (VAERS).

METHODS

We searched VAERS for US reports where an excess dose of vaccine was administered to a person received from 1/1/2007 through 1/26/2018. We reviewed medical records for all serious reports and a random sample of non-serious reports. The most common AEs among reports of excess dose of vaccine administered were compared with the corresponding AEs for all vaccines reported to VAERS during the same period.

RESULTS

Out of 366,815 total VAERS reports received, 5067 (1.4%) reported an excess dose of vaccine was administered; 3898 (76.9%) did not describe an adverse health event (AHE). The most common vaccines reported were trivalent inactivated influenza (15.4%), varicella (13.9%), hepatitis A (11.4%), and measles, mumps, rubella, varicella (11.1%). Among reports where only AHEs were reported, the most common were pyrexia (12.8%), injection site erythema (9.7%), injection site pain (8.9%), and headache (6.6%). The percentage of AHEs among these reports was comparable to all reports submitted to VAERS during the same study period.

CONCLUSION

More than three-fourths of reports of an excess dose of vaccine did not describe an AHE. Among reports where an AHE event was reported, we did not observe any unexpected conditions or clustering of AEs.

Review of vaccination in pregnancy to prevent pertussis in early infancy

Maternal pertussis vaccination has been introduced in several countries to protect infants from birth until routine infant vaccination takes place. This review assesses existing evidence on the effectiveness and safety of immunization in pregnancy. The search was finalized in April 2017 and was based on searches using several databases. The selection criteria included any experimental or observational study reporting on the immunogenicity, effectiveness or safety of vaccination with a pertussis-containing vaccine in pregnant women and their infants. Following de-duplication and exclusions, we identified 8395 studies, which were reduced to 46 for inclusion. The overall risk of bias was low, with the exception of some early studies and pharmacovigilance safety data. The evidence demonstrates efficient transplacental transfer of maternal antibodies in infants whose mothers were vaccinated with Tdap or Tdap/IPV in pregnancy, with good evidence that this protects against disease in young infants. Safety studies covering more than 150 000 women vaccinated mostly in the late second or third trimesters are generally consistent and provide reassurance of no significant increased risk of recognized maternal conditions or of adverse events (including congenital anomalies) in infants born to vaccinated women. The clinical significance of reduced seroconversion to pertussis following routine immunization is not yet clear, but no increased risk of pertussis in infants whose mothers were vaccinated in pregnancy was found following primary immunizations in North American and English studies. Most post-booster studies suggest that any blunting effect is short-lived and that longer-term protection in infants from active immunization is not compromised.

Prenatal Tetanus, Diphtheria, Acellular Pertussis Vaccination and Autism Spectrum Disorder

: media-1vid110.1542/5803567555001PEDS-VA_2018-0120Video Abstract BACKGROUND: Increasing vaccination of pregnant women makes it important to assess safety events potentially linked to prenatal vaccination. This study investigates the association between prenatal tetanus, diphtheria, acellular pertussis (Tdap) vaccination and autism spectrum disorder (ASD) risk in offspring.

METHODS

This is a retrospective cohort study of mother-child pairs with deliveries January 1, 2011 to December 31, 2014 at Kaiser Permanente Southern California hospitals. Maternal Tdap vaccination from pregnancy start to delivery date was obtained from electronic medical records. A diagnosis of ASD was obtained by using International Classification of Diseases, Ninth and Tenth Revision codes. Children were managed from birth to first ASD diagnosis, end of membership, or end of follow-up (June 30, 2017). Cox proportional hazards models estimated the unadjusted and adjusted hazard ratios (HRs) for the association between maternal Tdap vaccination and ASD, with inverse probability of treatment weighting to adjust for confounding.

RESULTS

Women vaccinated were more likely to be Asian American or Pacific Islander, be nulliparous, have a higher education, receive influenza vaccination prenatally, and give birth at term. ASD was diagnosed in 1341 (1.6%) children, and the incidence rate was 3.78 per 1000 person years in the Tdap exposed and 4.05 per 1000 person years in the unexposed group (HR: 0.98, 95% confidence interval: 0.88-1.09). The inverse probability of treatment weighting-adjusted analyses revealed that prenatal Tdap vaccination was not associated with an increased ASD risk (HR: 0.85, 95% confidence interval: 0.77-0.95).

CONCLUSIONS

Prenatal Tdap vaccination was not associated with an increased ASD risk. We support recommendations to vaccinate pregnant women to protect infants, who are at highest risk of death after pertussis infection.

Pertussis Immunisation in Pregnancy Safety (PIPS) Study: A retrospective cohort study of safety outcomes in pregnant women vaccinated with Tdap vaccine

BACKGROUND

New Zealand has funded the administration of tetanus, diphtheria and acellular pertussis (Tdap) vaccine during pregnancy to prevent infant pertussis since 2013. The aim of this study was to assess the safety of Tdap vaccine administered to pregnant women as part of a national maternal immunisation programme.

METHODS

We conducted a national retrospective observational study using linked administrative New Zealand datasets. The study population consisted of pregnant women eligible to receive funded Tdap vaccination from 28 to 38 weeks gestation in 2013. Primary study outcomes were based on prioritised adverse events for the assessment of vaccine safety in pregnant women, as defined by WHO and Brighton Collaboration taskforces. We examined the effect of Tdap vaccination on prioritised maternal outcomes using Cox proportional hazard models. Adjusted hazard ratios controlled for key confounding variables.

RESULTS

In the cohort of 68,550 women eligible to receive funded antenatal Tdap vaccination during 2013, 8178 (11.9%) were vaccinated and 60,372 (88.1%) were unvaccinated. The use of Tdap in pregnancy was not associated with an increase in the rate of primary outcomes, including preterm labour; pre-eclampsia; pre-eclampsia with severe features; eclampsia; gestational hypertension; fetal growth restriction; or post-partum haemorrhage. Tdap also did not increase secondary outcomes, including gestational diabetes mellitus; antenatal bleeding; placental abruption; premature rupture of membranes; preterm delivery; fetal distress; chorioamnionitis; or, maternal fever during or after labour. Lactation disorders was the only secondary maternal outcome with a significantly increased hazard ratio. Tdap vaccine had a protective effect on pre-eclampsia with severe features, preterm labour, preterm delivery, and antenatal bleeding.

CONCLUSION

We did not detect any biologically plausible adverse maternal outcomes following Tdap vaccination during pregnancy. This study provides further assurance that Tdap administration during pregnancy is not associated with unexpected safety risks.

Prevention of Pertussis, Tetanus, and Diphtheria with Vaccines in the United States: Recommendations of the Advisory Committee on Immunization Practices (ACIP)

This report compiles and summarizes all recommendations from CDC's Advisory Committee on Immunization Practices (ACIP) regarding prevention and control of tetanus, diphtheria, and pertussis in the United States. As a comprehensive summary of previously published recommendations, this report does not contain any new recommendations and replaces all previously published reports and policy notes; it is intended for use by clinicians and public health providers as a resource. ACIP recommends routine vaccination for tetanus, diphtheria, and pertussis. Infants and young children are recommended to receive a 5-dose series of diphtheria and tetanus toxoids and acellular pertussis (DTaP) vaccines, with one adolescent booster dose of tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine. Adults who have never received Tdap also are recommended to receive a booster dose of Tdap. Women are recommended to receive a dose of Tdap during each pregnancy, which should be administered from 27 through 36 weeks' gestation, regardless of previous receipt of Tdap. After receipt of Tdap, adolescents and adults are recommended to receive a booster tetanus and diphtheria toxoids (Td) vaccine every 10 years to assure ongoing protection against tetanus and diphtheria.

Major Birth Defects after Vaccination Reported to the Vaccine Adverse Event Reporting System (VAERS), 1990 to 2014

BACKGROUND

Major birth defects are important infant outcomes that have not been well studied in the postmarketing surveillance of vaccines given to pregnant women. We assessed the presence of major birth defects following vaccination in the Vaccine Adverse Event Reporting System (VAERS), a national spontaneous reporting system used to monitor the safety of vaccines in the United States.

METHODS

We searched VAERS for reports of major birth defects during January 1, 1990, through December 31, 2014. We excluded birth defects from vaccines that had been studied in pregnancy registries or other epidemiological studies (e.g., human papilloma virus, varicella, measles/mumps/rubella, and anthrax vaccines). Birth defects were categorized into trimester of vaccination and classified based on the organs and/or systems affected. If several birth defects affecting different systems were described, we classified those as multiple body systems. Empirical Bayesian data mining was used to assess for disproportionate reporting.

RESULTS

We identified 50 reports of major birth defects; in 28 reports, the vaccine was given during the first trimester; 25 were reports with single vaccines administered. Birth defects accounted for 0.03% of all reports received by VAERS during the study period and 3.2% of pregnancy reports; reported defects affected predominately the musculoskeletal (N = 10) or nervous (N = 10) systems. No unusual clusters or specific birth defects were identified.

CONCLUSION

This review of the VAERS database found that major birth defects were infrequently reported, with no particular condition reported disproportionally. Birth defects after routine maternal vaccination will continue to be monitored in VAERS for signals to prompt future studies. Birth Defects Research 109:1057-1062, 2017. © 2017 Wiley Periodicals, Inc.

Patient reaction to Tdap vaccination in pregnancy

BACKGROUND

The current obstetrical recommendation is to routinely administer the tetanus, diphtheria, and acellular pertussis (Tdap) vaccination during every pregnancy regardless of a patient's prior history. There are minimal data that have prospectively evaluated solicited patient response to this treatment plan. The study objective was to evaluate patient reaction following receipt of Tdap vaccination during pregnancy.

METHODS

This was a prospective observational study conducted from May 2014 through March 2016. The study design involved solicited patient reaction within 1-7days after the administration of the Tdap vaccine. Data collected included pain or soreness, swelling, and/or redness at the injection site, as well as, fever and generalized body aches. Statistical analysis involved simple percentages with Poisson binomial 95% confidence intervals with Chi-square and Fisher's exact comparisons where appropriate.

RESULTS

A total of 737 patients were evaluated and 496 (67%, 95% Confidence Interval [CI] 64-71%) were found to have at least 1 reaction to the vaccination and 187 (25%, 95% CI 22-29%) had 2 reactions or more. Overall, the majority of patients stated that the vaccination was tolerated. However, 24 (3%, 95% CI 2-5%) of the study population stated that they would not accept receipt of Tdap in a subsequent pregnancy because of the response that occurred in the current pregnancy.

CONCLUSION

These data demonstrate that maternal reactions following receipt of Tdap are common (two-thirds of the study population). A potential concern is the finding that some patients might refuse a repeat vaccination in a subsequent pregnancy due to these reactions. If further research reveals similar findings, a pertussis only vaccine for pregnant patients might need to be evaluated.

Tetanus-diphtheria-acellular pertussis vaccination for adults: an update

Although tetanus and diphtheria have become rare in developed countries, pertussis is still endemic in some developed countries. These are vaccine-preventable diseases and vaccination for adults is important to prevent the outbreak of disease. Strategies for tetanus, diphtheria, and pertussis vaccines vary from country to country. Each country needs to monitor consistently epidemiology of the diseases and changes vaccination policies accordingly. Recent studies showed that tetanus–diphtheria–acellular pertussis vaccine for adults is effective and safe to prevent pertussis disease in infants. However, vaccine coverage still remains low than expected and seroprevalence of protective antibodies levels for tetanus, diphtheria, and pertussis decline with aging. The importance of tetanus–diphtheria–acellular pertussis vaccine administration should be emphasized for the protection of young adult and elderly people also, not limited to children.

The safety of maternal immunization

Maternal vaccination offers the opportunity to protect pregnant women and their infants against potentially serious disease. As both pregnant women and their newborns are vulnerable to severe illness, the potential public health impact of mass maternal vaccination programs is remarkable. Several high-income countries recommend seasonal influenza and acellular pertussis vaccines, and many developing countries recommend immunization against tetanus during pregnancy. There is a significant amount of literature supporting the safety of vaccination during pregnancy. As other vaccines are newly introduced for pregnant women, routine systems for monitoring vaccine safety in pregnant women are needed. To facilitate meta-analyses and comparison across systems and studies, future research and surveillance initiatives should utilize the same criteria for defining adverse events following immunization among pregnant women. At least 2 areas require further exploration: 1) identification of pregnancy outcomes associated with concomitant and closely spaced vaccines; 2) evaluation of possible improvement in birth outcomes associated with maternal vaccination. Given the public health impact of maternal vaccination, the existing evidence supporting the safety of vaccination during pregnancy should be used to reassure pregnant women and their providers and improve vaccine uptake in pregnancy.