The impact of additional pertussis vaccine doses on disease incidence in children and infants

The Present and Future Aspects of Life-Long Pertussis Prevention: Narrative Review with Regional Perspectives for Türkiye

Pertussis, caused by Bordetella pertussis, remains one of the most widespread, contagious, and vaccine-preventable diseases. It results in notable morbidity and mortality as well as severe medical, social, and economic burden. Despite high global vaccine coverage, pertussis continues to be a significant epidemiologic problem, with outbreak episodes every few years just as in the pre-vaccination era. In Türkiye, there is a lack of comprehensive data on the current burden of pertussis in different age and risk groups, leading to underdiagnosis and underreporting of the disease, especially in adults who are often not considered at risk. Available data from Türkiye also reveal inadequate levels of protective antibodies in preterm newborns, emphasizing the need for additional preventive measures. Authors stated that improving physician awareness of pertussis symptoms in patients with prolonged cough, increasing access to routine pertussis tests, and conducting surveillance studies would aid in accurate diagnosis and reporting in Türkiye. As the Turkish Ministry of Health Antenatal Care Management Guide suggests routine second and third pregnancy check-up visits at weeks 18-24 and 28-32 correspondingly, this period can be considered the ideal vaccination time for Türkiye. Introducing a booster dose of Tdap at around 10 years of age or during national military service would reduce transmission and protect susceptible individuals. Identifying individuals at high risk of severe pertussis and prioritizing them for a booster dose is also crucial in Türkiye. Enhancing surveillance systems, increasing healthcare professionals' awareness through training, and organizing catch-up visits for missed vaccinations during the COVID-19 pandemic are mentioned as additional strategies to improve pertussis prevention in Türkiye. This review focuses on the global and regional burden of pertussis and obstacles to effective prevention and evaluates existing strategies to achieve lifelong pertussis prevention. Literature and current strategies were also discussed from a Turkish national standpoint.

Pertussis immunisation strategies to optimise infant pertussis control: A narrative systematic review

OBJECTIVE

Countries routinely offering acellular pertussis vaccine, where long-term protection is not sustained, have the challenge of selecting an optimal schedule to minimise disease among young infants. We conducted a narrative systematic review and synthesis of information to evaluate different pertussis immunisation strategies at controlling pertussis disease, hospitalisation, deaths, and vaccine effectiveness among young infants.

METHODS

We conducted a review of the literature on studies about the primary, booster, and/or maternal vaccination series and synthesised findings narratively. Countries offering the first three doses of vaccine within six-months of life and a booster on or before the second year or life were defined as accelerated primary and booster schedules, respectively. Countries offering primary and booster doses later were defined as extended primary and booster schedules. All search results were screened, and articles reviewed and reconciled, by two authors. The Risk of Bias in Non-randomised Studies of Intervention tool was used to evaluate the risk of bias.

FINDINGS

A total of 98 studies were included in the analyses and the following recurring themes were described: timing of vaccination, vaccine coverage, waning immunity/vaccine effectiveness, direct and indirect effectiveness, switching from an accelerated to extended schedule, impact of changes in testing. The risk of bias was generally low to moderate for most studies.

CONCLUSION

Comparing schedules is challenging and there was insufficient evidence to that one schedule was superior to another. Countries must select a schedule that maintains high vaccine coverage and reduced the risk of delaying the delivery vaccines to protect infants.

Bordetella pertussis in School-Age Children, Adolescents, and Adults: A Systematic Review of Epidemiology, Burden, and Mortality in the Middle East

Despite modern diphtheria-tetanus-pertussis (DTP) vaccines and high vaccine coverage, a resurgence of pertussis (whooping cough) has been observed globally. In North America and Europe, high vaccine coverage in children has led to a shift in the age-specific peak incidence of infection away from infants and towards older children and adolescents. However, much less is known about the prevalence of pertussis in older children and adults in the Middle East. A systematic search of MEDLINE, EMBASE, and BIOSIS was undertaken to identify studies published between 1 January 1990 and 17 June 2019, with information on pertussis epidemiology, burden of illness, and mortality in school-aged children, adolescents, and adults in the Middle East. Studies identified for inclusion were reviewed narratively because a statistical comparison was not possible because of the mix of methodologies used. The results showed that surveillance data are weak or missing in most Middle Eastern countries, and among 24 epidemiological studies identified, most were from Iran (14), Israel (4), and Turkey (3), with single studies from the United Arab Emirates and Iraq. Despite various surveillance periods, clinical definitions, and antibody cut-off values used across the studies, the reported seroprevalence of pertussis antibodies suggested that adolescents and adults are commonly exposed to pertussis in the community and that vaccine-acquired immunity from childhood wanes. Few countries in the Middle East include a diphtheria-tetanus-acellular pertussis (Tdap) booster for adolescents on the national schedule. Israel was the only country with epidemiological data in a population that received Tdap, and the study showed that after the introduction of the adolescent booster dose, there was decrease in pertussis among children aged 5–14 years. To conclude, results from the Middle East suggest that in common with other regions, pertussis is widely circulating and that it might be shifting towards older age groups.

A systematic review of the burden of pertussis disease in infants and the effectiveness of maternal immunization against pertussis

Introduction Infants too young to be fully immunized are the most vulnerable to severe pertussis disease. To close this susceptibility gap, passive infant immunization through vaccination of pregnant women against pertussis was first introduced in 2011 in the United States and has been extended since then to more than 40 countries. Areas covered We conducted two systematic literature searches to describe the worldwide burden of pertussis disease in infants <6 months of age since 2005, and the effectiveness and impact of maternal pertussis vaccination in preventing infant pertussis since 2011. Expert opinion Pertussis disease incidence rates in infants aged <2-3 months were substantial in all countries with available data, exceeding 1000 cases per 100,000 population during outbreaks. Virtually all pertussis deaths occurred in this age group. Data from Africa, Eastern Mediterranean, and Asia were limited, but suggest a similar or higher disease burden than in Europe or the Americas. Estimates of effectiveness of second/third trimester pertussis vaccination in preventing pertussis disease in <2-3 months old infants were consistently high (69%-93%) across the observational studies reviewed, conducted in various settings with different designs. Maternal vaccination programs appear to be achieving their goal of reducing the burden of disease in very young infants. Plain language summary What is the context? Pertussis, also known as whooping cough, is a highly contagious disease of the respiratory tract. Infants too young to be fully vaccinated are at the highest risk of severe pertussis disease, hospitalization, and death. Vaccinating pregnant women against pertussis with a Tdap vaccine is recommended in more than 40 countries as a safe and effective strategy to protect infants for the first months of life. What is new? This review summarizes recent literature describing the burden of pertussis disease in infants worldwide prior to the introduction of maternal vaccination programs; pertussis disease incidence rates in infants aged <2-3 months were substantial in all countries with available data, exceeding 1000 cases per 100,000 population during outbreaks. Immunization of pregnant women with a Tdap vaccine can prevent about 70-90% of pertussis disease and up to 90.5% of pertussis hospitalizations in infants under 3 months of age. What is the impact? Limited available data suggest that incidence rates of pertussis disease after the introduction of Tdap maternal immunization have declined in infants. Current knowledge supports the implementation of Tdap maternal immunization programs.

Did two booster doses for schoolchildren change the epidemiology of pertussis in Israel?

Pertussis is the only vaccine-preventable disease that has re-emerged in Israel. In the last two decades, despite high primary immunization coverage, crude incidence increased over tenfold, with especially high morbidity among infants and adolescents and with 19 infant deaths. Two pertussis vaccine boosters were added, in 2005 for 7-year-olds and in 2011 for 13-year-olds. We reviewed age group incidence from 1999 to 2016, before and after the booster program introduction. We compared three groups of 13-15 year-olds with identical primary immunization but different booster immunization histories. Vaccine effectiveness was calculated before and after adjustment for specific incidence in those aged 65 and over. Two years after one booster, adjusted vaccine effectiveness was 74.5%. Two years after two boosters, adjusted vaccine effectiveness was 91.8%. However, crude morbidity rates were not reduced. The booster program has been effective only among recipient groups. The program will be continued. Israel is now encouraging pregnant women to be vaccinated against pertussis to improve protection of infants.

[Recent progress in clinical research on pertussis]

Pertussis is a highly contagious respiratory disease. Despite the high vaccination coverage, re-emergence of pertussis has been reported in many countries over the past two decades. With the increase in the incidence of pertussis, there has been a shift in the epidemiological features: an increased incidence of pertussis has been noted in older children and adults, who normally lack typical clinical manifestations, and who may be easily missed according to current diagnostic references for pertussis. In order to achieve better prevention and treatment of pertussis, this review article summarized the recent research progress in the epidemiology, clinical features, etiology, diagnosis, treatment, and prevention of pertussis, particularly focusing on the diagnosis of pertussis in older children and adults.

Pertussis Across the Globe: Recent Epidemiologic Trends From 2000 to 2013

Pertussis has reemerged as a problem across the world. To better understand the nature of the resurgence, we reviewed recent epidemiologic data and we report disease trends from across the world. Published epidemiologic data from January 2000 to July 2013 were obtained via PubMed searches and open-access websites. Data on vaccine coverage and reported pertussis cases from 2000 through 2012 from the 6 World Health Organization regions were also reviewed. Findings are confounded not only by the lack of systematic and comparable observations in many areas of the world but also by the cyclic nature of pertussis with peaks occurring every 3-5 years. It appears that pertussis incidence has increased in school-age children in North America and western Europe, where acellular pertussis vaccines are used, but an increase has also occurred in some countries that use whole-cell vaccines. Worldwide, pertussis remains a serious health concern, especially for infants, who bear the greatest disease burden. Factors that may contribute to the resurgence include lack of booster immunizations, low vaccine coverage, improved diagnostic methods, and genetic changes in the organism. To better understand the epidemiology of pertussis and optimize disease control, it is important to improve surveillance worldwide, irrespective of pertussis vaccine types and schedules used in each country.

Strategies and new developments to control pertussis, an actual health problem

The aim of this article is to describe the current epidemiological situation of pertussis, as well as different short-term strategies that have been implemented to alleviate this threat. The state of the art of the development of new vaccines that are expected to provide long-lasting immunity against pertussis was also included.

The induction of breast milk pertussis specific antibodies following gestational tetanus-diphtheria-acellular pertussis vaccination

BACKGROUND

Center for Disease Control and Prevention recommends vaccination of pregnant women with tetanus-diphtheria-acellular pertussis (Tdap).

AIM

To measure pertussis specific antibodies, total protein and their ratio in breast milk following gestational Tdap vaccination.

METHODS

Women who received Tdap after the 20th week of pregnancy were recruited and unvaccinated women served as controls. Breast milk total protein, immunoglobulin A (IgA) to pertussis toxin (PT), filamentous hemagglutinin (FHA) and immunoglobulin G (IgG) to PT, FHA and pertactin (PRN) were measured. To overcome the dilution that occurs in the transition from colostrum to mature breast milk, we calculated pertussis specific antibody to total protein ratio.

RESULTS

Pertussis specific IgA was the predominant pertussis immunoglobulin in the colostrum of Tdap vaccinated women with the geometric mean concentrations (GMCs) of IgA to FHA higher than for IgA to PT, 24.12 ELISA units/milliliter (EU/mL) vs. 8.18EU/mL, respectively, p<0.004. There were differences between the vaccinated women and controls in the GMCs of IgA to FHA and IgG to PRN in the colostrum, 24.12EU/mL vs. 6.52EU/mL, p=0.01 and 2.46EU/mL vs. <0.6EU/mL, p=0.03, respectively. The GMCs of total protein showed significant decline over 8 weeks in the vaccinated women and controls, p<0.004. Among vaccinated women, there was significant decline in the GMCs of IgA to PT and FHA over 8 weeks, p<0.001. The geometric mean ratio of IgA to FHA to total protein also declined significantly over 8 weeks in the vaccinated women, p<0.01, demonstrating a true decrease, however, pertussis IgA was measurable at 8 weeks.

CONCLUSIONS

Select colostrum pertussis antibody levels were significantly higher among women vaccinated with Tdap during pregnancy compared with unvaccinated women. Among vaccinated women, maximal levels of pertussis specific IgA were in the colostrum but still detected at 8 weeks. Lactation may augment infant's protection against pertussis.

Effectiveness and cost-effectiveness of different immunization strategies against whooping cough to reduce child morbidity and mortality

INTRODUCTION

In the last years there has been a significant increase in reported cases of pertussis in developed countries, in spite of high rates of childhood immunization. Health institutions have recommended different vaccination strategies to reduce child morbidity and mortality: vaccination of adolescents and adults, pregnant women, people in contact with the newborn (cocoon strategy) and health care workers. The aim of this paper is to review the scientific evidence supporting these recommendations.

METHODS

Systematic review on the effectiveness and cost-effectiveness of the above strategies for the reduction of morbidity and mortality from pertussis in infants under 12 months. The electronic databases Medline, PreMedline, Embase, CRD, Cochrane Central, and Trip Database were consulted from 1990 to October 2012. The evidence was assessed using the GRADE system.

RESULTS

There were eight studies on the efficacy or safety of the strategies analyzed, and 18 economic evaluations. Direct evidence on the efficacy of these strategies is scarce. Economic evaluations suggest that vaccination of adolescents and adults would be cost-effective, although there is major uncertainty over the parameters used.

CONCLUSIONS

From the perspective of health technology assessment, there is insufficient evidence to recommend the vaccination strategies evaluated.