Effectiveness of maternal pertussis vaccination in Singapore: A test-negative case-control study

Pertussis vaccination (Tdap -Tetanus-diphtheria-acellular pertussis) for pregnant women has been recommended since November 2017 in Singapore. In this prospective test-negative case-control study from 2018 to 2019, we aimed to evaluate vaccine effectiveness (VE) against pertussis infection and pertussis-related intensive care unit (ICU) admission according to Tdap (Tetanus-diphtheria-acellular pertussis) during pregnancy and/or infant pertussis vaccination. A total of 58 children (26 cases, 32 controls) were recruited with 4 ICU admissions. The median age was 3 months (interquartile range [IQR] 1.50–4.56 months). Overall, 25.9 % of mothers had received antenatal Tdap vaccination and 43.1 % of infants received pertussis vaccination, majority only 1 dose. Tdap in pregnancy alone without infant vaccine or with 0–1 infant dose had a VE of 97.62 % (95 % confidence interval [CI] 53.25–99.88 %), 98.17 % (95 %CI 66.61–99.9 %) respectively, against pertussis infection and 71.9 % (95 %CI 0.0–98.64), 75.86 % (95 % CI 0.0–98.78) respectively, against ICU admissions. Conclusion: Maternal Tdap vaccination was highly protective against infant pertussis and should be routinely recommended for all pregnant women.     

Assessing determinants of the intention to accept a pertussis cocooning vaccination: A survey among healthcare workers in maternity and paediatric care

ObjectiveTo assess the intention to accept a pertussis cocooning vaccination and to examine the determinants that influence this intention among healthcare workers (HCWs) in maternity and paediatric care.DesignCross-sectional survey.SettingMaternity assistants, midwives, and paediatric nurses in the Netherlands.MethodsWe developed a 123-item questionnaire based on a literature review and the Reasoned Action Approach (a social cognitive model of behaviour). We used the questionnaire to explore the determinants of intention to accept pertussis cocooning vaccination among the HCW groups. We also assessed the behavioural beliefs underlying HCWs’ attitudes towards pertussis cocooning. We used correlation and regression analyses to assess univariate and multivariate associations in the study variables.ResultsAltogether, 486 maternity assistants, 320 midwives, and 200 paediatric nurses completed the questionnaire; 45%–63% reported their intentions to accept pertussis vaccination. Attitude, anticipated affect regarding non-acceptance, and decisional uncertainty were uniquely associated with the intention to accept a pertussis vaccination. The respondents’ attitude towards pertussis cocooning vaccination was further explained by their general vaccination beliefs, agreement with a policy advice to vaccinate HCWs, the perceived cost-benefit ratio, and the perceived personal responsibility to prevent pertussis in patients.ConclusionAbout half of the participating HCWs reported their intentions to accept a pertussis cocooning vaccination. Attitude, anticipated affect regarding non-acceptance, and decisional uncertainty came forward as the most important determinants of intention. This study helps build the evidence base describing the determinants of the intention to accept a pertussis cocooning vaccination among HCWs.     

Effectiveness of maternal pertussis vaccination in preventing infection and disease in infants: The NSW Public Health Network case-control study

BackgroundInfants are at the highest risk of severe complications – including death – as a result of pertussis infection. Controlling pertussis in this group has been challenging, particularly in those too young to be vaccinated. Following revised national recommendations in March 2015, the state of New South Wales, Australia, introduced a funded maternal vaccination campaign at 28 – 32 weeks of gestation using a 3-component tetanus-diphtheria-acellular pertussis vaccine (dTpa; Boostrix, GSK). This study aimed to assess the effectiveness of maternal vaccination and add to the growing body of evidence for this strategy.MethodsA 1:1 matched case-control study was conducted between 16 August 2015 and 17 August 2016. Cases were laboratory or doctor notified, laboratory confirmed (nucleic acid testing or culture) and aged <6 months at onset. Each control infant was randomly selected from public hospital births in the same geographical area in the period up to 3 days before and after the case’s birthdate. Odds ratios (OR) were calculated using conditional logistic regression. Vaccine effectiveness (VE) was calculated as 1 – OR.FindingsIn total, 117 cases and 117 controls were recruited. The overall VE estimate was non-significantly protective for infants <6 months old (VE 39%, 95% CI −12 to 66%). Higher VE was observed for infants <3 months old (VE 69%, 95% CI 13–89%) and against hospitalisation (VE 94%, 95% CI 59–99%).InterpretationMaternal pertussis vaccination with a 3-component acellular vaccine was found to be highly effective at preventing severe disease in infants, but was less effective at preventing disease which did not require hospitalisation. The overall VE reported in this study was lower than in prior studies and suggests that maternal vaccination, while an effective strategy at preventing severe pertussis, is less effective at protecting against infection or mild disease.     

Dose-dependent effectiveness of acellular pertussis vaccine in infants: A population-based case-control study

BackgroundPertussis is a vaccine-preventable disease which is most severe in young infants. More than two decades after the introduction of acelluar pertussis vaccines (aPV) in national immunization programs in many countries worldwide, a resurgence of pertussis has been recognized. Suboptimal effectiveness of aPV has been blamed as one major reason but only few studies have evaluated dose-dependent vaccine effectiveness (VE) provided by aPV in current practice.MethodsWe performed a population-based retrospective case-control study by comparing pertussis immunization data of children 2.5 months to 2 years of age hospitalized for pertussis and residing in Switzerland with immunization data of a random control sample of children aged 2 years and residing in Switzerland. VE was defined as the percentage of hospitalizations avoided by number of aPV doses. It was calculated as 1-infection rate ratio (IRR)*100. IRR was calculated by dividing infection rates of vaccinated children and infection rates of unvaccinated children. To get dose specific VE, infection rates were stratified by number doses received.ResultsVE against hospitalization due to pertussis increased significantly with each consecutive aPV dose in a “3 + 1” primary course in infants: 42.1% (95% CI: 11.3–62.6), 83.9% (70.2–92.1), 98.2% (96.1–99.3), and 100% (97.9–100) after the 1st, 2nd, 3rd, and 4th dose, respectively.ConclusionAcellular pertussis vaccines continue to demonstrate protection against hospitalization due to pertussis in infants and young children. Therefore, together with advancing immunization of pregnant women and household contacts, better control of severe pertussis in young infants can be achieved by timely initiation of immunization.     

Assessing determinants of the intention to accept a pertussis cocooning vaccination: A survey among Dutch parents

IntroductionPertussis cocooning is one of the strategies aiming to prevent the potential harm of pertussis in infants by vaccinating (among others) their parents. Several countries adopted this strategy, but uptake is a problem. Determinants of parental uptake are important in the design of an effective vaccination programme. Therefore, this study aims to assess parents’ intention to accept a pertussis cocooning vaccination and its determinants.MethodsA 98 item questionnaire was developed based on a theoretical framework, assessing parents’ intention to accept a pertussis cocooning vaccination and its personal and psychosocial determinants. In addition, beliefs underlying parents’ attitude towards pertussis cocooning vaccination were assessed. Both logistic and linear regression analysis were used to assess univariate and multivariate associations amongst study variables.ResultsParents returned 282 questionnaires. The majority of the parents (78%) reported a positive intention to accept a pertussis cocooning vaccination. Attitude (OR 6.6, p < .001), anticipated negative affect in response to non acceptance (OR 1.65, p < .001), anticipated negative affect in response to acceptance (OR 0.55, p .040) and decisional uncertainty (OR 0.52, p .002) were significantly associated with intention. General vaccination beliefs (β 0.58, p < .001), moral norm (β 0.22, p < .001), perceived susceptibility of pertussis in children (β 0.10, p.004), and efficacy outcome expectations (β 0.15, p.011) were significant correlates of attitude towards pertussis cocooning vaccination.ConclusionThe parental intention to accept a pertussis cocooning vaccination in this study is rather high. Targeting the identified determinants of parents’ acceptance in a pertussis cocooning vaccination programme is crucial to secure that intention is translated into actual vaccination uptake.     

Burden of pertussis among young infants in Malaysia: A hospital-based surveillance study

BackgroundThe case fatality rate and the risk of complications due to pertussis is very high in infants. Asia has the second highest childhood pertussis burden. The study aimed to assess the prevalence, clinical complications, and mortality rates of pertussis disease requiring hospitalization among young infants in Malaysia.MethodsThe study was a one-year, hospital-based, multi-site surveillance of infants less than six months of age with symptoms consistent with pertussis and a cross-sectional analysis of their mothers for recent pertussis infection. Information was obtained from medical records and interviews with the parents. Pertussis diagnosis was confirmed for all infants through serum anti-PT titration test or PCR test.Results441 possible cases of pertussis were included in this study. Of these, 12.7 % had laboratory confirmation of pertussis. Infants with confirmed pertussis had significantly higher rates of cyanosis (37.5 % vs 8.6 %; p < 0.0001) and apnea (12.5 % vs 3.9 %; p = 0.027) than test-negative infants. Most infants from both groups were in recovery/recovered at discharge. Those with confirmed pertussis had higher case fatality rate than test-negative cases (5.4 % vs 1.0 %; p = 0.094), but the difference did not reach significance. The majority of confirmed pertussis cases (89.3 %) occurred in infants too young to be fully vaccinated or under-vaccinated for their age. Both test-negative and confirmed pertussis resulted in work-day losses and incurred costs for both parents.ConclusionsA high pertussis disease burden persists in infants less than six months of age, especially among those un- and under-vaccinated. Maternal and complete, on-time infant vaccination is important to reduce disease burden.     

The impact of parental postpartum pertussis vaccination on infection in infants: A population-based study of cocooning in Western Australia

During a pertussis epidemic in 2011–2012 the Western Australian (WA) Department of Health implemented a ‘cocooning’ programme, offering free pertussis-containing vaccine (dTpa) to new parents. We assessed the impact of vaccinating parents with dTpa on the incidence of pertussis infection in newborns.Births in WA during 2011–2012 were linked to a register of parental pertussis vaccinations and to notified reports of laboratory-proven pertussis in children <6 months of age. Parents who received dTpa during the four weeks after their child's birth were defined as ‘vaccinated postpartum.’ Cox proportional-hazards methods were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for the risk of pertussis infection among infants born to parents vaccinated postpartum vs. unvaccinated parents, adjusted for maternal age, geographic region, timing of birth, and number of siblings.Of 64,364 live-births, 43,480 (68%) infants had at least one vaccinated parent (60% of mothers and 36% of fathers). After excluding records where parent(s) were either vaccinated prior to the birth, vaccinated >28 days after the birth, the vaccination date was uncertain, or the child died at birth (n = 42), the final cohort contained 53,149 children, 118 of whom developed pertussis. There was no difference in the incidence of pertussis among infants whose parents were both vaccinated postpartum compared to those with unvaccinated parents (1.9 vs 2.2 infections per 1000 infants; adjusted HR 0.91; 95%CI 0.55–1.53). Similarly, when assessed independently, maternal postpartum vaccination was not protective (adjusted HR 1.19; 95%CI 0.82–1.72). Supplemental sensitivity analyses which varied the time period for parental vaccination and accounted for under-reporting of vaccination status did not significantly alter these findings.In our setting, vaccinating parents with dTpa during the four weeks following delivery did not reduce pertussis diagnoses in infants. WA now provides dTpa vaccine to pregnant women during the third trimester.     

Sources of pertussis infection in young infants: A review of key evidence informing targeting of the cocoon strategy

Background

The relative contribution of different categories of contact in transmitting pertussis to very young infants, who experience the most severe morbidity, is the most important single factor determining the likely benefit of pertussis vaccination of their close contacts (the “cocooning” strategy).

Objective

To identify, evaluate the quality of and summarise existing data on potential sources of infant pertussis infection in high income countries, focussing on infants under 6 months old.Data sources: Online databases MEDLINE and EMBASE. Additional studies were identified from the reference lists of relevant articles.Study selection and analysis: Study quality was evaluated by standardised criteria, based on the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement. Pooled estimates of the proportion of pertussis cases attributable to various contact sources were calculated using data from the highest quality studies.

Results

Nine studies met the inclusion criteria; seven included data on contacts of hospitalised infants less than 6 months old. Case definitions and methods of contact ascertainment were variable. Most identified sources were from the household, of which 39% (95%CI 33–45%) were mothers, 16% (95%CI 12–21%) fathers, and 5% (95%CI 2–10%) grandparents. Estimates for siblings (16–43%) and non-household contacts (4–22%) were more heterogeneous. For 32–52% of infant cases, no source was identified. Asymptomatic pertussis infection was found in 8–13% of contacts evaluated.

Conclusions

These data suggest that the greatest potential impact of pertussis vaccination of adults to prevent severe disease in young infants comes from vaccinating mothers, followed by fathers, with grandparents having a minor role. Siblings varied in importance and, given recent data regarding waning immunity in vaccinated children, need further study. Non-household sources are also well documented, highlighting the potential limitations of the cocoon strategy to prevent severe infant disease.     

百日咳感染的家庭聚集性特征分析

目的 了解百日咳就诊患者年龄分布、传染源并分析传播模式。方法 对2012年1月至2013年8月于西安市儿童医院就诊的婴幼儿和/或儿童病例及其流行病学相关病例（有咳嗽症状的密切接触者）进行百日咳实验室检测并确诊,采用Excel 2007软件统计百日咳就诊病例及其传染源或后续病例的临床症状和年龄分布。结果 254例百日咳临床疑似病例和54例流行病学相关病例经实验室检测分别确诊165例和38例。实验室确诊的临床病例中<1岁者共138例（83.6%）;流行病学相关病例中>20岁者36例（94.7%）,所有流行病学相关病例均被误诊或漏诊。实验室诊断病例中其传染源为父母共计25起（78.1%）,并可见由儿童传播至成年人的现象。结论 百日咳的流行呈家庭聚集性。就诊者中多为<1岁婴儿,而成年人病例是婴幼儿病例的主要传染源,且存在严重误诊或漏诊。有必要调整目前百日咳加强免疫策略。     

A retrospective study of administration of vaccination for hepatitis B among newborn infants prior to hospital discharge at a midwestern tertiary care center

ObjectivesInfants are at high risk of developing chronic, life-threatening disease as a result of hepatitis B virus infection. Universal vaccination of infants against hepatitis B virus, before discharge from the hospital after delivery is recommended as a measure to eradicate infection and associated mortality and morbidity. The purpose of this study was to determine rates of perinatal hepatitis B vaccine (Hep B) administration at a tertiary care center in Iowa and to assess the impact of maternal factors on Hep B uptake.MethodsData concerning mother–infant pairs that received care at one institution from 1/2009 to 4/1/2013 were extracted from the system's electronic medical record. Characteristics of study participants were compared using chi-square tests. Multivariate logistic regression was used to assess the association between each factor and vaccination status, controlling for other characteristics.ResultsOf 5663 mother–infant pairs, 5175 (91.4%) infants received Hep B within 7 days after delivery. The majority of those not vaccinated had a medical indication to delay vaccination. Single women were significantly more likely to have an infant not vaccinated, after adjustment for all other factors. Women of minority groups were significantly less likely to have an infant who lacked Hep B at hospital discharge than Caucasian women.ConclusionsSignificant improvements have occurred in Hep B rates in the state and region. Infants of single mothers may be at the greatest risk for lacking vaccination at hospital discharge.     

Age-specific effectiveness following each dose of acellular pertussis vaccine among infants and children in New Zealand

BackgroundThough it is believed the switch from whole cell to acellular pertussis vaccine has contributed to the resurgence of pertussis disease, few studies have evaluated vaccine effectiveness (VE) and duration of protection provided by an acellular vaccine schedule including three primary doses but no toddler-age dose. We assessed this schedule in New Zealand (NZ), a setting with historically high rates of pertussis disease, and low but recently improved immunisation coverage. We further evaluated protection following the preschool-age booster dose.MethodsWe performed a nested case-control study using national-level healthcare data. Hospitalised and non-hospitalised pertussis was detected among children 6 weeks to 7 years of age between January 2006 and December 2013. The NZ National Immunisation Register provided vaccination status for cases and controls. Conditional logistic regression was used to calculate dose-specific VE with duration of immunity examined by stratifying VE into ages aligned with the immunisation schedule.ResultsVE against pertussis hospitalisation was 93% (95% confidence interval [CI]: 87, 96) following three doses among infants aged 5–11 months who received three compared to zero doses. This protection was sustained through children’s fourth birthdays (VE ⩾ 91%). VE against non-hospitalised pertussis was also sustained after three doses, from 86% (95% CI: 80, 90) among 5–11 month olds to 84% (95% CI: 80, 88) among 3-year-olds. Following the first booster dose at 4 years of age, the protective VE of 93% (95% CI: 90, 95) among 4-year-olds continued through 7 years of age (VE ⩾ 91%).ConclusionsWe found a high level of protection with no reduction in VE following both the primary course and the first booster dose. These findings support a 3-dose primary course of acellular vaccine with no booster dose until 4 years of age.     

Epidemiology of pertussis in a country with high vaccination coverage

Introduction

Pertussis has been a preventable disease in Catalonia since 1965, but the annual number of cases remains high. The aim of this study was to analyze the epidemiology of pertussis in Catalonia and its implications for control purposes.

Methods

An epidemiological study was carried out in Catalonia between 2004 and 2008. Pertussis cases reported to the Department of Health were collected and disease reports were filled out with the case information. Incidence rates, rate ratios (RR) and their 95% confidence intervals (CI) were calculated.

Results

963 cases were reported: 555 (57.6%) were confirmed and 408 (42.4%) were suspected cases. The reported incidence rate was 2.01 × 10⁻⁵ person years in 2004 and 4.34 in 2008. The biggest increase in cases between 2004 and 2008 was observed in the ≥35 years age group (RR: 6.98; 95%CI: 2.11-36.36). 303 (31.5%) patients were hospitalized, of whom 93.7% were aged <1 year. Clinical differences were observed in paroxysmal cough (83.8% in suspected and 76.4% in confirmed cases, p = 0.005), posttussive vomiting (47.1% and 36.1%, respectively, p = 0.001), apnoea (13.7% and 21.3%, respectively, p = 0.003) and fever (20.1% and 12.4%, respectively, p = 0.001).

Conclusion

Pertussis incidence rates increased during the study period, with the greatest increase occurring in the ≥35 years age group. A booster dose of vaccine in young people could reduce the circulation of B. pertussis in adolescents and adults and indirectly reduce the incidence in children.     

Increasing postpartum rate of vaccination with tetanus,diphtheria, and acellular pertussis vaccine by incorporating pertussis cocooning information into prenatal education for group B streptococcus prevention

BackgroundTo evaluate whether incorporating pertussis cocooning information into prenatal education for group B streptococcus (GBS) prevention increased postpartum rate of vaccination with tetanus, diphtheria, and acellular pertussis (Tdap) vaccine.MethodsWe performed a retrospective pre-intervention/post-intervention study of postpartum women at a teaching hospital in Taiwan. We compared the frequency of Tdap vaccination during the pre-intervention (May 1, 2009 to December 31, 2010) and post-intervention (March 1, 2011–March 31, 2012) time periods. The clinical intervention was incorporation of pertussis cocooning information into prenatal education for GBS prevention to pregnant women presented during a prenatal visit at 35–37 weeks of gestation. Postpartum Tdap vaccination rate during the pre-intervention and post-intervention periods was compared. We also specifically examined group differences in the percentage of women who received postpartum Tdap vaccination to explore factors that influenced their decision regarding Tdap vaccine.ResultsTdap vaccination was more likely during the post-intervention period compared with the pre-intervention period (2268 of 3186 [71.2%] compared with 2556 of 5030 [55.6%]; p < .001). Comparisons between each subgroup of pre-intervention and post-intervention women showed that incorporating pertussis information into prenatal education for GBS prevention was beneficial except for women of maternal age 30–34 years and women living in rural areas.ConclusionsPrenatal GBS screening activities represent an opportunity for healthcare providers to offer pertussis cocooning information to eligible pregnant women to improve rates of postpartum Tdap vaccination.     

Comparing the effect of parental education via both lecture and film upon vaccination uptake for children under one year of age: A cluster randomized clinical trial

Background and AimVaccination is the most cost-effective action in preventing infectious diseases. Despite Iran's success in high vaccination coverage, in some areas there is a delay in vaccination. The aim of this study was to determine and compare the effect of education on immunization via lecture and film upon parental delay in vaccination uptake for children under 12 months of age.MethodsA multicentre cluster-randomized clinical trial with comprehensive urban health centres (CUHCs) in Shooshtar city, Khuzestan province, Iran as the unit of randomization was conducted. Overall, 8 CUHCs were randomized to receive education either via film (n = 165) or lecture (n = 164). In order to assign CUHCs to two groups, a simple random sampling method of coin tossing was used. Parents with children under 12 months and with a history of delayed vaccination were included in the study. Consecutive sampling was performed until the number needed for the cluster was reached. Interventions were delivered in small groups of 5–8 participants. Demographical data and clinical histories were collected from parents directly via a personal characteristic’s questionnaire. Clinical data was extracted from vaccination records, the child's vaccine card and the vaccine information registration system. Statistical analyses of intervention effects were performed as per-protocol analysis.ResultsIn terms of individual characteristics and vaccine information significant differences between the two groups were only observed in relation to the parent of the participant, the child's gender, the number of children in the family, and timely injection of the vaccine in the previous child (p < 0.05). The chance of delay in vaccination after the intervention, without and considering the effect of intervening variables was 78 % and 74 % higher in the lecture group than in the film group, respectively (OR = 1.786, CI = 1.152–2.774 vs AOR = 1.743, CI = 1.011–3.007). Overall, 37.6 % of children in the film-based education group and 51.8 % of children in the lecture-based education group received their next vaccine with a delay of more than 7 days.ConclusionEducation delivered via film can reduce the delay in vaccination more effectively. These findings, along with those of other studies conducted around the world suggest that multimedia education should be considered more widely in the field of education in children's vaccination.     

Differences in avidity of IgG antibodies to pertussis toxin after acellular pertussis booster vaccination and natural infection

Background

Pertussis toxin (PT) is a specific virulence factor of Bordetella pertussis and it is included in all acellular pertussis vaccines (aP). Although immunity after infection seems to persist longer than that after vaccination, the exact mechanism(s) is not known. Primary aim of this study was to develop an ELISA method for measuring avidity index (AI) of IgG-anti-PT antibodies and to compare antibody responses after booster vaccination and infection. Secondary aim was to evaluate if the AI-ELISA has potential in the serodiagnosis of pertussis.

Material

Serum samples from a total of 409 subjects were included in the study. Paired sera were taken from 97 adolescents who received booster vaccine ten years ago (dTpa-004) and from 80 young adults who received a second booster dose ten years after the previous booster vaccine (dTpa-040). Thirty-two paired sera from culture-confirmed pertussis patients, 161 single sera from serologically diagnosed patients and 39 single sera from healthy controls were included. AI of IgG-anti-PT antibodies were determined with newly developed ELISA using diethylamine (DEA) as a bond breaking agent. The IgG-anti-PT antibodies were measured by standardized ELISA.

Results

A significant increase was found in antibody concentrations and AI between PRE and one month POST vaccination ten years ago [GMC for antibody: 7.9 IU/ml vs. 98.3 IU/ml (p = 0.0001); for AI: 40.4% vs. 56.1% (p = 0.0001)]. Similar result was observed after the second booster dose [GMC for antibody: 9.2 IU/ml vs. 92.4 IU/ml (p = 0.0001); for AI: 36.1% vs. 59.5% (p = 0.0001)] and between the first and second sera of culture-confirmed patients [GMC for antibody: 6.9 IU/ml vs. 285.1 IU/ml (p = 0.0001); for AI: 40.5% vs. 68.4% (p = 0.0001)]. Healthy controls showed lower levels of both antibodies and AI.

Conclusions

Our results suggest that there may be difference in quality and quantity of antibodies to PT after vaccination and after infection. Furthermore, AI could be a help for vaccine studies.     

A multisite study of pertussis vaccine effectiveness by time since last vaccine dose from three Canadian provinces: A Canadian Immunization Research Network study

BackgroundPertussis remains poorly controlled relative to other diseases targeted by childhood vaccination programs. We combined estimates from four population-based studies of pertussis vaccine effectiveness (VE) in three Canadian provinces using a meta-analytic approach to improve precision and explore regional variation in VE and durability of protection.MethodsStudies were conducted in Alberta, Manitoba, and Ontario over periods ranging from 1996 to 2015. Adjusted log odds ratios (OR; VE = 100*[1-OR]) of the effect of vaccination on pertussis risk were estimated by time since last vaccination in each study and pooled using DerSimonian and Laird random-effects models. We used the I² statistic to estimate between-study heterogeneity and assessed methodological and clinical heterogeneity through subgroup analyses of study design and age.ResultsData on 3,270 pertussis cases and 23,863 controls were available. Pertussis VE declined from 86% (95% CI 79%-90%, I² = 81.5%) at < 1 year since last vaccination to 51% (11%-74%, I² = 80.9%) by ≥ 8 years. Effect estimates were the most heterogeneous in the least and most elapsed time periods since last vaccine dose. This was attributable mostly to variation between provinces in the distribution of age groups and number of vaccine doses received within time periods, as well as study design and small numbers in the most elapsed time period.Interpretation: Consistent trends of decreasing pertussis VE with increasing time since last vaccination across three Canadian provinces indicate the need for immunization schedules and vaccine development to optimize protection for all individuals, especially for adolescents and young adults at greatest risk of infection.     

Effectiveness of acellular pertussis vaccine and evolution of pertussis incidence in the community of Madrid from 1998 to 2015

IntroductionPertussis is a communicable disease that primarily affects infants. Vaccination has led to an important reduction in the incidence of the disease, however, resurgence of the disease has been observed. This study aimed to analyze the incidence of pertussis and assess the vaccination effectiveness (VE) of different schedules of acellular pertussis vaccination in the community of Madrid.MethodsPertussis cases notified to the Mandatory Disease Reporting System from 1998 to 2015 were analyzed. Five comparison periods were created: 1998–2001 (reference), 2002–2005, 2006–2009, 2010–2012 and 2013–2015. The incidence ratio (IR) between inter-epidemic periods was analyzed using a Poisson regression. VE was calculated using the screening method. Vaccine status data were collected from the vaccine registry.ResultsIn total, 3855 cases were notified. Inter-epidemic periods were observed every 3–4 years. The incidence increased (IR: 5.99, p < 0.05) in the 2013–2015 period, particularly among infants younger than 1 month (IR: 32.41, p < 0.05). Vaccination data were available in 89% of cases. For those receiving the last dose at ≤6-month VE was 89.9% (95% confidence interval (CI): 87.3–92.0) after one year of follow-up, and 85.5% (95% CI: 82.4–88.1) after 11 years of follow-up. For those receiving the last dose at 18-months VE decreased from 98.8% (95% CI: 98.3–99.1) to 85.1% (95% CI: 81.9–87.7) in the same period, and for those receiving the last dose at 4-year VE decreased from 99.6% (95% CI: 99.3–99.7) to 79.3% (95% CI: 74.6–83.1).ConclusionsB. pertussis is circulating in our population, as shown by the epidemic peaks and increased incidence of pertussis in recent years. VE increased with the number of doses and decreased with the follow-up period. The effect of this and other vaccination strategies must be monitored to control the disease.     

Pertussis vaccine effectiveness in a frequency matched population-based case-control Canadian Immunization Research Network study in Ontario,Canada 2009–2015

Background

Resurgences of pertussis have occurred in several high-income countries, often linked to waning of immunity from acellular pertussis vaccines. The degree of waning observed has varied by study design and setting. In Ontario, pertussis has not shown a substantial resurgence in the past decade. The routine immunization schedule comprises three priming doses in infancy, toddler and pre-school doses, and an adolescent dose at 14–16?years of age.

Uptake of a government-funded pertussis-containing booster vaccination program for parents of new babies in Victoria,Australia

IntroductionAn epidemic of Bordetella pertussis in Victoria, Australia, led to the implementation of a Government-funded vaccination program for parents of new babies. The rationale was to protect unimmunised infants from infection by vaccinating parents with a pertussis-containing vaccine. This is known as cocooning.AimTo estimate uptake of the vaccine among parents of new babies, two-and-a-half years after the program was implemented.MethodsA state-wide cross-sectional survey of parents was conducted to ascertain vaccine uptake, and to identify where and when the vaccination took place. Surveys were administered between 15 February and 14 March 2012, inclusive.ResultsOf 6308 surveys distributed, 2510 completed surveys were returned (response rate 40%). Ninety-five surveys completed outside the study period were excluded, leaving 2415 available for analysis. Overall, 1937 (80%) mothers and 1385 (70%) fathers were vaccinated in relation to the birth of their most recent child. A majority of mothers were vaccinated in hospital (62%). Most fathers were vaccinated by a general practitioner (72%). The most common point at which mothers were vaccinated was before their child turned two weeks of age (65%). Fathers’ vaccination time-point varied more widely: during pregnancy (25%); before their child turned two weeks of age (29%); and when their child was between two and eight weeks of age (28%).ConclusionResults of this survey indicated excellent uptake of the vaccine among both mothers and fathers under the Government-funded cocooning program. The findings are suggestive of an effective communications program designed to raise awareness of the risks of pertussis, and to promote availability of the funded vaccination program. The results may contribute to policy implementation of adult immunisation programs such as cocooning.     

Effectiveness of two pertussis vaccines in preterm Danish children

Reduced immunogenicity in preterm children has been observed for pertussis vaccines. How immunogenicity relates to clinical protection is not well-established for pertussis, and the corresponding reduction, if any, in post-licensure vaccination effectiveness among preterm children has not been determined. We conducted a nationwide cohort study of 879,424 Danish children including 1553 cases of pertussis hospitalisation. The effectiveness of pertussis vaccination, both whole-cell and acellular, was evaluated in preterm and full-term children. The effectiveness of a completed primary series of pertussis vaccination, whole-cell or acellular, was similar in preterm and full-term children.