Japan's experience in pertussis epidemiology and vaccination in the past thirty years

BECC438b TLR4 agonist supports unique immune response profiles from nasal and muscular DTaP pertussis vaccines in murine challenge models

The protection afforded by acellular pertussis vaccines wanes over time, and there is a need to develop improved vaccine formulations. Options to improve the vaccines involve the utilization of different adjuvants and administration via different routes. While intramuscular (IM) vaccination provides a robust systemic immune response, intranasal (IN) vaccination theoretically induces a localized immune response within the nasal cavity. In the case of a Bordetella pertussis infection, IN vaccination results in an immune response that is similar to natural infection, which provides the longest duration of protection. Current acellular formulations utilize an alum adjuvant, and antibody levels wane over time. To overcome the current limitations with the acellular vaccine, we incorporated a novel TLR4 agonist, BECC438b, into both IM and IN acellular formulations to determine its ability to protect against infection in a murine airway challenge model. Following immunization and challenge, we observed that DTaP + BECC438b reduced bacterial burden within the lung and trachea for both administration routes when compared with mock-vaccinated and challenged (MVC) mice. Interestingly, IN administration of DTaP + BECC438b induced a Th1-polarized immune response, while IM vaccination polarized toward a Th2 immune response. RNA sequencing analysis of the lung demonstrated that DTaP + BECC438b activates biological pathways similar to natural infection. Additionally, IN administration of DTaP + BECC438b activated the expression of genes involved in a multitude of pathways associated with the immune system. Overall, these data suggest that BECC438b adjuvant and the IN vaccination route can impact efficacy and responses of pertussis vaccines in pre-clinical mouse models.

Differential impacts of vaccine scandal by ethnic and socioeconomic factors: Evidence from China

Widespread vaccination against important diseases plays a key role for global health security, particularly in the context of the COVID-19 pandemic. However, building and maintaining trust in immunization services remains challenging because of doubts about quality and safety of vaccines. China has periodically faced mounting pressure and even public outrage triggered by incidents of poor-quality vaccines. We aimed to evaluate the impact of the diphtheria, pertussis, and tetanus (DPT) vaccine scandal of 2018 in China and the ensuing misinformation on vaccination, and investigate differential responses to the scandal by ethnic and socioeconomic factors. With data from January 2017 to December 2018 in Sichuan province, China, we used a difference-in-differences (DID) method to compare the changes in the county-level monthly DPT vaccinations against the hepatitis B vaccinations, both before and after the DPT vaccine scandal. We found that the number of DPT vaccinations decreased by 14.0 percent in response to the vaccine scandal and ensuing misinformation. The number of vaccinations in minority regions, under-developed regions, and regions with poor medical resources decreased more than in non-minority regions, developed regions, and regions with good medical resources (24.5 versus 10.1 percent, 17.3 versus 8.3 percent, and 17.0 versus 8.7 percent, respectively). People did more online searching for "Substandard vaccine" and "DPT vaccine" after the scandal, with the socioeconomically advantaged group searching more compared with the socioeconomically disadvantaged group. The results suggest the urgent need to make true information about the vaccine easily accessible over the internet, especially for the socioeconomically disadvantaged groups. Our findings for China can also have implications for immunization service planning for better safeguarding public health in other countries, particularly developing ones.

[Increasing the efficiency of a mobile EPI strategy using injectable polio vaccine in Africa]

Introduction

In 1980, partners initiated a mobile simplified EPI (Expanded programme on immunization) strategy for immunizing, with mobile teams, rural and urban populations in Western Africa. This strategy delivered EPI vaccines in two sessions: 1) 3-8 month-old children: BCG-Diphteria Tetanus Pertussis + reinforced killed Polio vaccine; 2) 9-15 month-old children: Diphteria Tetanus Pertussis + reinforced killed Polio vaccine, Measles-Yellow Fever. This strategy was compared to WHO-UNICEF extended EPI strategy, but results were never published in the context of a planned rapid polio eradication with oral polio vaccine.

Methods

For comparison with standard WHO-UNICEF extended EPI strategy, using oral polio vaccine in four sessions, all the costs generated by these two strategies in 1988 have been collected in two adjacent zones in Burkina Faso, Western Africa: 203,642 inhabitants for WHO-UNICEF extended EPI strategy (Yako); 109,483 inhabitants for mobile simplified EPI strategy (Gourci). An EPI coverage survey at the end of this year has been done in these two adjacent zones with efficiency (costs per fully immunized child) computed.

Results

In Africa, the simplified mobile EPI strategy using reinforced killed polio vaccine was found two times more efficient (12.71 US$ per fully immunized child) than WHO-UNICEF extended EPI strategy using oral polio vaccine (29.67 US$ per fully immunized child), even if DTP-reinforced killed polio vaccine (0.52 US$ per dose) was more expensive than DTP and oral polio vaccine (0.14 US$ for the combined dose). The missed opportunities uncaught up would have doubled coverage in the WHO-UNICEF extended EPI strategy, versus only a 10% increase with the mobile simplified EPI strategy. The main reason for uncaught up missed opportunities in WHO extended EPI strategy was the absence of requested vaccine delivered by a health agent when attending population at meeting point, due to insufficient cold box volume carried on his moped for transport of vaccine.

Discussion

After 30 years, since 1990, of poliomyelitis eradication in Africa using oral polio vaccine and with non-added costs in this study of polio mass campaigns, these results should be published to review EPI strategy.

CpG 1018® adjuvant enhances Tdap immune responses against Bordetella pertussis in mice

Bordetella pertussis is the causative agent of whooping cough (pertussis), a severe respiratory disease that can be fatal, particularly in infants. Despite high vaccine coverage, pertussis remains a problem because the currently used DTaP and Tdap vaccines do not completely prevent infection or transmission. It is well established that the alum adjuvant is a potential weakness of the acellular vaccines because the immunity provided by it is short-term. We aimed to evaluate the potential of CpG 1018® adjuvant to improve antibody responses and enhance protection against B. pertussis challenge in a murine model. A titrated range of Tdap vaccine doses were evaluated in order to best identify the adjuvant capability of CpG 1018. Antibody responses to pertussis toxin (PT), filamentous hemagglutinin (FHA), or the whole bacterium were increased due to the inclusion of CpG 1018. In B. pertussis intranasal challenge studies, we observed improved protection and bacterial clearance from the lower respiratory tract due to adding CpG 1018 to 1/20th the human dose of Tdap. Further, we determined that Tdap and Tdap + CpG 1018 were both capable of facilitating clearance of strains that do not express pertactin (PRN^-), which are rising in prevalence. Functional phenotyping of antibodies revealed that the inclusion of CpG 1018 induced more bacterial opsonization and antibodies of the Th1 phenotype (IgG2a and IgG2b). This study demonstrates the potential of adding CpG 1018 to Tdap to improve immunogenicity and protection against B. pertussis compared to the conventional, alum-only adjuvanted Tdap vaccine.

Trust collapse caused by the Changsheng vaccine crisis in China

BACKGROUND

The public acceptance and implementation of vaccination programs is essential to prevent infectious diseases. However, vaccine adverse events may cause public panic and eventually lead to an increasing number of populations who were hesitant or refuse to participate in these vaccination programs. In 2018, the Changsheng vaccine crisis broke out in mainland China, and 252,600 unqualified DTP vaccines were reported to be used for child vaccination. In this study, we observed media and public reactions toward the vaccine crisis.

METHODS

This study conducted Internet surveillance by four mainstream indicators from July 15th to August 7th, including social media (WeChat, Sina Weibo), online news and Baidu search index. We also analyzed the emotional perceptions of people in crisis through an online questionnaire survey.

RESULTS

During the crisis, huge number of articles emerged on Internet, 125,882,894 articles (including forwarding) on WeChat friends circle, 1,877,660 Sina Weibo posts, 648,265 online news and 4,986,521 Baidu search indexes. Most of these articles were negative and expressed the public's weak confidence to the China-made vaccines. Public confidence in vaccines was undermined by the actions of the manufacturer and the government.

CONCLUSIONS

The DTP vaccine crisis led to panic about immunization and eroded trust in the immunization program and in the government. Restoring public confidence in Chinese-made vaccines will take a long time, and meticulous management in vaccine production, and strict government regulation will help to alleviate public anxiety about vaccine safety and ultimately restore confidence.

No pain no gain? Adjuvant effects of alum and monophosphoryl lipid A in pertussis and HPV vaccines

Development of non-infectious subunit vaccines is hampered by a slow pipeline of new adjuvants to replace or enhance alum in part because expectations of safety are high. Transient vaccine side effects are not clinical priorities because they cause no lasting harm and vaccine development has appropriately been focused on avoidance of serious adverse events. As a result, surprisingly little is known about the extent to which side effects caused by a vaccine's reactogencicity are predictive of successful immunization outcomes. Recent clinical studies of pertussis and human papillomavirus vaccines adjuvanted with alum or the TLR4 agonist monophosphoryl lipid A can be used to advance understanding of the relationship between vaccine side effects and immunization outcomes.

The impact of a vaccine scare on parental views, trust and information needs: a qualitative study in Sydney, Australia

BACKGROUND

Vaccine safety scares can undermine public confidence in vaccines and decrease immunisation rates. Understanding and addressing parental concerns arising during such scares can assist in lessening their impact. In Australia in April 2010 there was a temporary suspension of influenza vaccine for children under 5 years of age after reports of an increase in the rate of adverse events following vaccination. This qualitative study aimed to explore the impact of the vaccine suspension on parental knowledge, attitudes, trust, information needs, and intent related to influenza vaccination and broader immunisation programs.

METHODS

Semi-structured interviews were conducted with 25 parents of children attending childcare centres in Sydney, Australia, between June 2010 and May 2011. Centres were selected to include parents from a range of socioeconomic backgrounds. Interview transcripts were coded and analysed using an approach informed by grounded theory.

RESULTS

Findings indicated that, for those who recalled the vaccine suspension, there was a lasting sense of uncertainty and confusion and a perceived lack of information. Parents had distinct information needs following the vaccine suspension, especially in regards to vaccine safety, testing and recommendations. For many, influenza vaccination intent was conditional on receipt of information from a trusted, authoritative source allaying safety concerns. Importantly, the impact of the scare was contained to influenza vaccines only, and not other vaccine programs.

CONCLUSIONS

Parental concerns and information gaps following a vaccine safety scare need to be actively addressed. We provide policy and practice suggestions for proactively managing such incidents, particularly in relation to communication of timely, targeted information to parents and immunisation providers.

Vaccine hesitancy, vaccine refusal and the anti-vaccine movement: influence, impact and implications

Despite being recognized as one of the most successful public health measures, vaccination is perceived as unsafe and unnecessary by a growing number of parents. Anti-vaccination movements have been implicated in lowered vaccine acceptance rates and in the increase in vaccine-preventable disease outbreaks and epidemics. In this review, we will look at determinants of parental decision-making about vaccination and provide an overview of the history of anti-vaccination movements and its clinical impact.

Controversies in vaccine mandates

Policies that mandate immunization have always been controversial. The controversies take different forms in different contexts. For routine childhood immunizations, many parents have fears about both short- and long-term side effects. Parental worries change as the rate of vaccination in the community changes. When most children are vaccinated, parents worry more about side effects than they do about disease. Because of these worries, immunization rates go down. As immunization rates go down, disease rates go up, and parents worry less about side effects of vaccination and more about the complications of the diseases. Immunization rates then go up. For teenagers, controversies arise about the criteria that should guide policies that mandate, rather than merely recommend and encourage, certain immunizations. In particular, policy makers have questioned whether immunizations for human papillomavirus, or other diseases that are not contagious, should be required. For healthcare workers, debates have focused on the strength of institutional mandates. For years, experts have recommended that all healthcare workers be immunized against influenza. Immunizations for other infections including pertussis, measles, mumps, and hepatitis are encouraged but few hospitals have mandated such immunizations-instead, they rely on incentives and education. Pandemics present a different set of problems as people demand vaccines that are in short supply. These issues erupt into controversy on a regular basis. Physicians and policy makers must respond both in their individual practices and as advisory experts to national and state agencies. The articles in this volume will discuss the evolution of national immunization programs in these various settings. We will critically examine the role of vaccine mandates. We will discuss ways that practitioners and public health officials should deal with vaccine refusal. We will contrast responses of the population as a whole, within the healthcare setting, and in the setting of pandemic influenza.

Comparison of acellular pertussis-based combination vaccines by Japanese control tests for toxicities and laboratory models for local reaction

Two batches each of diphtheria -- tetanus -- acellular pertussis vaccine (DTaP) and that combined with inactivated polio vaccine purchased from the U.S.A., European and Asian markets were compared with Japanese DTaPs by Japanese control tests for DTaP and laboratory models for local reaction. All the imported vaccines met Japanese criteria for toxicities of acellular pertussis vaccine except for the toxicity to mouse weight gain (body weight decreasing (BWD) toxicity). When injecting into mouse footpad, rabbit back skin and mouse quadriceps muscle, the imported vaccines induced much severer inflammation and tissue injury comparing to Japanese DTaPs irrespective of animal species, injection site and injection volume suggesting that these vaccines may induce stronger local reactogenicity.

Parents' vaccination comprehension and decisions

We report on 30 in-depth mental models interviews with parents discussing vaccination for their children, both in general terms and in response to communications drawn from sources supporting and opposing vaccines. We found that even parents favourable to vaccination can be confused by the ongoing debate, leading them to question their choices. Many parents lack basic knowledge of how vaccines work, and do not find the standard information provided to them to be particularly helpful in explaining it. Those with the greatest need to know about vaccination seem most vulnerable to confusing information. Opportunities for education may be missed if paediatricians do not appreciate parents' specific information needs.

Highly sensitive histamine-sensitization test for residual activity of pertussis toxin in acellular pertussis vaccine

Histamine-sensitization test method based on histamine-sensitizing death is widely used for controlling residual activity of pertussis toxin in acellular pertussis vaccines. The test method evaluates the residual activity according to the death of mice injected with a test vaccine after histamine challenge and the test result, therefore, depends on the sensitivity of mice. A highly sensitive test method based on change in rectal temperature of mice has been used in Japan for many years but has limited feasibility in other countries. We examined the possibility of a test method using dermal temperature measured by infrared thermometer to reduce animal suffering instead of rectal temperature. The dermal temperature method was shown to be as sensitive as the rectal temperature method. Furthermore, the dermal as well as rectal temperature methods can evaluate the activity of a test vaccine in relative to a reference preparation so as to allow direct comparison of the test results among different laboratories. The activity by means of the dermal temperature method was also found to be well consistent with that by the rectal temperature method.

Antigenic divergence between Bordetella pertussis clinical isolates from Moscow, Russia, and vaccine strains

We analyzed temporal changes in the frequencies of the ptxA, prn, fim2, and fim3 alleles in Bordetella pertussis strains isolated from pertussis patients in Moscow, Russia, from 1948 to 2004. The three strains used for the whole-cell vaccine harbored the alleles ptxA2, ptxA4, prn1, fim2-1, and fim3A. Vaccine-type alleles of ptxA (ptxA2 and ptxA4) were characteristic for all prevaccination strains and for 96% of the strains isolated in the 1960s and 1970s. At the beginning of the 1970s, ptxA2 and ptxA4 were replaced by the ptxA1 allele. In the 1980s and to the present, strains with ptxA1 were predominant in the B. pertussis population. All prevaccination strains harbored the prn1 allele, which corresponds to the vaccine-type allele. In subsequent years, the proportion of strains with the prn1 allele decreased and the proportion of prn3 and prn2 strains increased. From 2002 to 2004 strains with prn2 or prn3 were predominant in the B. pertussis population. The vaccine-type alleles fim2-1 and fim3A were found in all prevaccination strains and in 92% of the strains isolated from 1960 to 1989. The fim2-2 and fim3B alleles were first observed at the beginning of the 1980s. In subsequent years, these strains became predominant. Together with waning immunity, the antigenic divergence between vaccine strains and clinical isolates observed in the Moscow area may explain the persistence of pertussis, despite the high rates of vaccine coverage. The results demonstrate that the selection of B. pertussis strains for vaccine manufacturing must be based on a thorough study of the B. pertussis population.

The pertussis vaccine controversy in Great Britain, 1974-1986

This historical essay analyzes the role played by Great Britain in the pertussis vaccine controversy of the 1970s and 1980s. Public backlash against this vaccine not only took place earlier in Britain than the United States, but also was so widespread that a series of whooping cough epidemics soon followed. As with the more recent dispute involving measles-mumps-rubella (MMR) vaccine and autism, the United Kingdom played a primary role in defining, promoting, and ultimately exporting this controversy. This essay seeks to explain this phenomenon by situating it in Britain's long history of suspicion regarding vaccines evident among both the public and the medical profession, a theme dating back to the compulsory vaccination laws of the 19th century. It argues that anti-vaccinationism, far from being simply a new development related to the public's lack of awareness of childhood vaccine-preventable illness, actually represents a revival of a much older movement.

Chinese hamster ovary (CHO) cell clustering does not correlate with in vivo histamine-sensitization when measuring residual activity of aldehyde-treated pertussis toxin (PT)

CHO cell clustering test failed to detect a reversion to PT toxicity of a commercial DTaP vaccine batch that failed to pass the test for reversion to histamine sensitizing (HS) activity. Efficacy of CHO cell clustering assay was, accordingly, evaluated using purified PT treated with graded concentrations of formaldehyde at 37 degrees C for 24h. The formaldehyde-treated PT was shown to lose CHO cell clustering activity to the level of 0.01% by the mild treatment while retaining 3.7-20.3% of HS activity which were far over the levels of commercial vaccines. When a reversion to toxicity of the aldehyde-detoxified PT was examined by incubating at 37 degrees C for three weeks, CHO cell clustering test again failed to detect the reversion to toxicity of the PT which showed a remarkable reversion to HS activity. These findings suggested that CHO cell clustering test might have an efficacy limitation in predicting in vivo activity of aldehyde-treated PT.

Which strategy for pertussis vaccination today?

Pertussis (whooping cough) remains an epidemic disease responsible for infant and child morbidity and mortality, and is perceived as a serious public health problem. Since the widespread use of whole-cell pertussis vaccines in the 1940s, vaccination programs have varied greatly between countries. National specificity is a function of several factors. The most important are: vaccine efficacy and tolerability;vaccine coverage and distribution; and vaccine acceptance by parents and professionals. During the 1970s, Sweden, England, Wales and Japan provided contrasting examples of the attitude of health authorities to the use of whole-cell vaccines. The increase in pertussis incidence was noted as a consequence of active opposition to this vaccine. The re-emergence of pertussis in the 1990s, in countries with high vaccination coverage and increased incidence of disease in individuals >15 years and <6 months of age, has drawn attention to the role of booster doses of pertussis vaccines and their introduction into regular vaccination programs. The use of acellular vaccines for booster doses for adolescents and adults would seem unambiguous because of their decreased reactogenicity, although the exact schedule has yet to be established. The choice between the two kinds of vaccines is more difficult for primary courses, where safety and efficacy profiles are similar, and the attitude towards acellular vaccines varies from country to country. In this case, the strategy adopted results from the national history of pertussis infection and from the quality of the available whole-cell vaccine. Two contrasting examples are the US, where acellular vaccines were licensed for the primary series in the 1990s, and the UK, where whole-cell vaccines are exclusively used for primary immunization. The changing epidemiology of pertussis, and its local diversification, would suggest that at present it is difficult to define a single worldwide strategy with only one kind of vaccine and one schedule. In order to control pertussis incidence, each country should continue to determine the best national vaccination program established in very close relation to the past and present epidemiological situation and available healthcare resources.

Distribution of pertussis antibodies among different age groups in Japan

We examined the distribution of antibody levels against pertussis toxin (PT) and filamentous hemagglutinin (FHA) among a healthy Japanese population aged from 0 to 77 years. Levels of both antibodies in 1108 serum samples collected in 1994 from nine prefectures were assayed using polystyrene ball ELISA. The ratio of individuals positive (>or=10 ELISA U/ml) for anti-PT and anti-FHA antibodies at ages ranging from 0 to 3 years increased rapidly with the increase in the population vaccinated over three times with acellular pertussis (aP) vaccine. However, the ratio of those positive for anti-PT antibody tended to decrease until 6-8 years of age and to increase again from 9 to 19 years among the vaccinated population, although the ratio of individuals positive for anti-FHA antibody remained constant at 80-100% in children and adolescents over 3 years old. Moreover, positivity for anti-PT antibody was high (>or=50 ELISA U/ml) in some serum samples collected from adolescents and young adults, suggesting recent symptomatic or asymptomatic infection with circulating Bordetella pertussis. On the other hand, 50-60% of infants below 12 months of age was below the detection limit (1.0 ELISA U/ml) for anti-PT and anti-FHA antibodies, and most early infants were not vaccinated for pertussis. Since intermittent circulation of B. pertussis remains among the Japanese population, complete vaccination with aP vaccine for all infants should be highly recommended to prevent pertussis.

Storage at −3°C for 24 h alters the immunogenicity of pertussis vaccines

The immunogenicity of pertussis antigens in an acellular and a whole-cell triple antigen vaccine used for childhood immunisation was assessed in murine models after storage of vaccines below 0 degree C. Swiss outbred and Balb/c mice received DTPa or DTPw vaccine or placebo. Vaccines were stored at 2-8 degrees C (ideal), or at -3 degrees C for 24 h. Pre and post immunisation IgG responses to pertussis toxin (PT), filamentous haemagglutinin (FHA) and pertactin (PRN) were measured using enzyme immunoassays (EIA). In Balb/c mice, responses to pertactin after receiving adversely stored DTPa were significantly reduced (P = 0.005, difference in GMCs 145.9% [24.6-385.4%]). A reduction in GMC to pertactin was also seen in response to adversely stored DTPw (P = 0.190,224.1% [83.8-599.2%]). Outbred mice receiving adversely stored DTPa had lower IgG antibody responses to FHA than those receiving correctly stored vaccine (P = 0.002,522.2% [26.1-2155.6%]). Outbred mice also had a significantly lower response to FHA after administration of DTPw (P = 0.009,14.0% [3.8-51.9%]). Responses to DTPa in both strains generally were greater than those to DTPw. Storage of pertussis vaccines below 0 degree C appears to alter the immunogenicity of PRN and FHA. Further study is required to determine the effects of such storage on vaccine protective efficacy.

From pertussis to tuberculosis: what can be learned?

Following the introduction of whole-cell pertussis vaccines into the general population, the number of cases of Bordetella pertussis disease declined dramatically. As disease incidence declined, the public's concern for pertussis as a national health problem gradually waned. However, a shift in paradigm occurred, and various groups and the media began to voice their concerns regarding adverse events associated with whole-cell vaccines. These events provided an impetus for the expedited development of safer and as efficacious subunit acellular vaccines. Effective public health leadership, public advocacy, scientific ingenuity, and collaborative interactions between government, academia, and industry culminated in the licensure of acellular pertussis vaccines. In this article, emphasis is placed on conceptualizing how a national public health agenda was implemented that allowed better insight into various public health concerns related to the development and use of acellular pertussis vaccines, concerns that were eventually translated into concrete actions. Knowledge of the environment in which this occurred may play a major role in relating the pertussis experience to tuberculosis vaccine development.

Acellular pertussis vaccines

Although whole-cell pertussis vaccines have been highly effective in preventing whooping cough, their common and burdensome adverse reactions have spurred the development of safer alternatives. Seven acellular vaccines are licensed in one or more countries; four have been licensed thus far in the United States, and more may follow. Although the licensed acellular pertussis vaccines differ in their immunogenicity, adverse reactions, and efficacy, all are effective and, compared with whole-cell vaccine, are associated with markedly fewer and milder adverse reactions.

Impact of anti-vaccine movements on pertussis control: the untold story

To assess the impact of anti-vaccine movements that targeted pertussis whole-cell vaccines, we compared pertussis incidence in countries where high coverage with diphtheria-tetanus-pertussis vaccines (DTP) was maintained (Hungary, the former East Germany, Poland, and the USA) with countries where immunisation was disrupted by anti-vaccine movements (Sweden, Japan, UK, The Russian Federation, Ireland, Italy, the former West Germany, and Australia). Pertussis incidence was 10 to 100 times lower in countries where high vaccine coverage was maintained than in countries where immunisation programs were compromised by anti-vaccine movements. Comparisons of neighbouring countries with high and low vaccine coverage further underscore the efficacy of these vaccines. Given the safety and cost-effectiveness of whole-cell pertussis vaccines, our study shows that, far from being obsolete, these vaccines continue to have an important role in global immunisation.

Epidemiology of pertussis

Throughout this century infants and young children have remained most susceptible to pertussis-related morbidity and mortality. In recent years infants younger than 6 months who are not old enough to have received three doses of the diphtheria-tetanus-pertussis vaccine and under-vaccinated preschool children have been at highest risk for pertussis-associated complications. Pertussis infection rates dropped dramatically after the whole cell pertussis vaccine came into widespread use, and an all-time low in reported cases in the United States was reached in 1976. Just as widespread immunization helped control the incidence of pertussis, it has probably been the primary factor in reducing pertussis-related mortality. Despite a stable or increasing vaccination rate in the United States since 1962, pertussis infection rates have been rising since the early 1980s. In 1993 the number of cases of pertussis reported represented an 82% increase over reported cases during the previous year and the highest incidence of pertussis since 1967. In 1993 pertussis became the most commonly reported vaccine-preventable disease among children in the United States younger than 5 years old. Growth of a susceptible adult population appears to be the primary factor contributing to the resurgence of pertussis in the United States; widespread immunization has reduced the potential for individuals to acquire exposure-induced immunity. It has been suggested that the majority of patients now infected with Bordetella pertussis are adults. Several studies have confirmed the importance of pertussis as the cause of persistent cough among teenagers and adults. As the diagnosis of pertussis goes unrecognized in these older patients and treatment is delayed or administered only partially, adolescents and adults have become an important source for transmission of B. pertussis infection to other household members, particularly infants and young children who are not adequately immunized.

A cellular pertussis vaccine (Infanrix-DTPa; SB-3). A review of its immunogenicity, protective efficacy and tolerability in the prevention of Bordetella pertussis infection

SB-3 (Infanrix-DTPa) is one of a new generation of vaccines for immunisation against pertussis (whooping cough), diphtheria and tetanus. It is a 3-component (pertussis toxin, filamentous haemagglutinin and pertactin) chemically inactivated acellular pertussis pertussis-diphtheria-tetanus toxoid (DTaP) vaccine, and it differs from conventional whole-cell pertussis-diphtheria-tetanus toxoid (DTwP) vaccines in that it comprises inactivated purified Bordetella pertussis antigens rather than whole cells of the bacillus. SB-3, like a number of other DTaP vaccines, elicits a similar or more often, a significantly greater immune response than various DTwP vaccines in healthy infants and young children. initial data from comparative studies indicate that SB-3 also remains immunogenic when given in combination with hepatitis B vaccine or concurrently administered with Haemophilus influenzae type b (HbOC) conjugate vaccine. A combination of SB-3 and H. influenzae type b tetanus (PRP-T) conjugate vaccine results in lower anti-PRP antibody response than when both vaccines are administered concurrently. Data from two large, multicentre, German and Italian studies in infants indicate that the protective efficacy of SB-3 against pertussis was significantly better than one DTwP (DTwP-CON) but similar to another one (DTwP-BW) under investigation. Compared with another DTaP vaccine (BIO-3), SB-3 was just as protective. Overall, the data from these 2 studies indicate that primary vaccination with SB-3 provides effective protection against pertussis, even under the stringent conditions of a household contact with typical pertussis. As the other DTaP vaccines, SB-3 is better tolerated than DTwP vaccines, with a significantly lower incidence of common adverse events such as local reactions (swelling, pain and a erythema), irritability, fever, persistent crying and local tenderness. Clinical experience with SB-3 thus far indicates that, like other DTaP vaccines, it is associated with significantly fewer common (non-serious) adverse events than DTwP vaccines. Less clear is whether it has any advantage over DTwP vaccines with respect to protective efficacy or over other DTaP vaccines with respect to tolerability and protective efficacy. Nevertheless, the available data support the use of SB-3 for infant immunisation, as well as providing a suitable basis for the development of new combination vaccines.

A controlled trial of two acellular vaccines and one whole-cell vaccine against pertussis. Progetto Pertosse Working Group

BACKGROUND

Concern about both safety and efficacy has made the use of whole-cell pertussis vaccines controversial. In some European countries, including Italy, the rate of vaccination against pertussis is low.

METHODS

We conducted a double-blind trial in Italy in which infants were randomly assigned to vaccination at two, four, and six months of age with an acellular pertussis vaccine together with diphtheria and tetanus toxoids (DTP); a DTP vaccine containing whole-cell pertussis (manufactured by Connaught Laboratories); or diphtheria and tetanus toxoids without pertussis (DT). The acellular DTP vaccine was either one containing filamentous hemagglutinin, pertactin, and pertussis toxin inactivated with formalin and glutaraldehyde (SmithKline Beecham) or one with filamentous hemagglutinin, pertactin, and genetically detoxified pertussis toxin (Chiron Biocine). Pertussis was defined as 21 days or more of paroxysmal cough, with infection confirmed by culture or serologic testing.

RESULTS

The efficacy of each vaccine, given in three doses, against pertussis was determined for 14,751 children over an average of 17 months, with cases included in the analysis if cough began 30 days or more after the completion of immunization. For both of the acellular DTP vaccines, the efficacy was 84 percent (95 percent confidence intervals, 76 to 89 percent for Biocine DTP and 76 to 90 percent for SmithKline DTP), whereas the efficacy of the whole-cell DTP vaccine was only 36 percent (95 percent confidence interval, 14 to 52 percent). The antibody responses were greater to the acellular vaccines than to the whole-cell vaccine. Local and systemic adverse events were significantly more frequent after the administration of the whole-cell vaccine. For the acellular vaccines, the frequency of adverse events was similar to that in the control (DT) group.

CONCLUSIONS

The two acellular DTP vaccines we studied were safe, immunogenic, and efficacious against pertussis, whereas the efficacy of the whole-cell DTP vaccine was unexpectedly low.

Outbreak of pertussis in highly immunized adolescents and its secondary spread to their families

An outbreak of pertussis was recognized in a highly immunized sixth-grade class of schoolchildren. Among 43 children aged 11-12 years in the class, 38 had been immunized with three doses or more of DTP containing whole-cell pertussis vaccine, two with two doses of DTP and three children were unimmunized. The last DTP vaccines had been given 6-10 years before the outbreak. A total of eight children with pertussis suffering paroxysmal coughing attacks for 3 weeks or more were identified, seven being fully immunized and one unimmunized. Among the eight cases, two were confirmed by both culture and serology and one by serology alone. The attack rate in fully immunized children was 18.4% (7/38). Secondary spread of pertussis was identified in five of the households from which the eight patients originated. A total of six cases of pertussis from these five households were identified, and two of these were culture-confirmed. These observations suggest that vaccine-induced immunity weakens considerably 6-10 years after vaccination, and that booster immunization with DTP instead of DT is therefore recommended for the control of pertussis.

Vaccine-preventable disease and immunization in the developing world

Vaccines have given health care providers control over a substantial portion of the morbidity and mortality in the developing world. Global efforts have immunized two-thirds of the world's children with DTP and polio vaccines; 72% have received BCG and 59% measles vaccine; but only 29% of pregnant women have received two doses of tetanus toxoid. In addition, vaccines against yellow fever, Japanese encephalitis, hepatitis B, rubella, and mumps and meningococcal polysaccharide vaccine are being used in specific regions of the world. New vaccine candidates will enhance the vaccine armamentarium over the next decade to include the causes of pneumonia, diarrhea, and meningitis: Haemophilus influenzae type b, pneumococcal and meningococcal protein conjugate vaccines, typhoid and rotavirus vaccine. Genetically engineered vaccine vehicles, genetic reassortants, and genetic deletions are being investigated as new vaccine candidates.

Genetic diversity and relationships in populations of Bordetella spp

Genetic diversity in 60 strains of three nominal Bordetella species recovered from humans and other mammalian hosts was assessed by analyzing electrophoretically demonstrable allelic variation at structural genes encoding 15 enzymes. Eleven of the loci were polymorphic, and 14 distinctive electrophoretic types, representing multilocus genotypes, were identified. The population structure of Bordetella spp. is clonal, and genetic diversity is relatively limited compared with most other pathogenic bacteria and is insufficient to justify recognition of three species. All isolates of Bordetella parapertussis were of one electrophoretic type, which was closely similar to 9 of the 10 electrophoretic types represented by isolates of Bordetella bronchiseptica. Bordetella pertussis 18-323, which is used in mouse potency tests of vaccines, is more similar genetically to isolates of B. bronchiseptica and B. parapertussis than to other isolates currently assigned to the species B. pertussis. Apart from strain 18-323, the isolates of B. pertussis represented only two closely related clones, and all isolates of B. pertussis from North America (except strain 18-323) were genotypically identical. Strain Dejong, which has been classified as B. bronchiseptica, was strongly differentiated from all of the other Bordetella isolates examined.

Efficacy of an acellular pertussis vaccine in Japan

To assess the efficacy of an acellular pertussis vaccine that has been used in Japan since 1981, 283 patients with pertussis were selected among patients with suspected pertussis seen at hospitals located around the Tokyo Metropolitan area from 1981 to 1983. The survey of secondary cases in household contacts showed that attack rates in children 0 to 6 years of age were 73.1% in unimmunized children, 15.0% in those fully immunized by whole-cell vaccines, and 15.4% in those given acellular vaccines. The efficacy of Japanese acellular pertussis vaccines was 79% and was not different from that of whole cell vaccines.

The incidence and type of reactions to plain and adsorbed DTP vaccines

The incidence and type of reactions after administration of plain and adsorbed diphtheria-tetanus-pertussis vaccine were recorded in a blind controlled prospective study of 2041 vaccinations in 1075 infants receiving routine childhood immunization. There was no significant difference in the total incidence or type of general reactions after plain and adsorbed vaccine, but local reactions were significantly less frequent after plain vaccine. General reactions were recorded after 41.5% of vaccinations with plain vaccine and after 40.8% of vaccinations with adsorbed vaccine. Local reactions were reported in 66.7% and 76.5% of recipients respectively. The most commonly reported systemic reactions were irritability and fever. Three recipients of plain vaccine and one of adsorbed vaccine suffered hyporesponsiveness or collapse. One recipient of each vaccine suffered a convulsion. No persisting sequelae were recorded.

Importance of culture in laboratory diagnosis of Bordetella pertussis infections

Nasopharyngeal secretions from 223 patients were examined for the presence of Bordetella pertussis and B. parapertussis by culturing on Regan-Lowe agar (J. Regan and F. Lowe, J. Clin. Microbiol. 6:303-309, 1977) and by direct fluorescent-antibody testing. B. pertussis was found in 38 patients; B. parapertussis was recovered from 2. Culturing was more sensitive (38 of 38 patients) than direct fluorescent-antibody testing (26 of 38 patients) for the detection of B. pertussis. Overgrowth by other organisms (7 of 223 patients) was uncommon. The patients with B. pertussis infections were generally less than 1 year old, had received no or one immunization, and had coughing spells but infrequently had whooping cough. Accurate diagnosis of B. pertussis infections should include culturing.

Risks and Benefits of Vaccinations

Any medical intervention is expected to prevent sickness and complications of a disease rather than to induce them. This is true for therapy as well as prophylaxis. Special formulas have been developed to calculate the risks and benefits of vaccinations simply but with sufficient accuracy. The risk ratio (Q) tells how many times the risk of contracting certain complications or even death from a disease is greater in unvaccinated than in vaccinated individuals. The risk difference (D) directly expresses the number of complications or deaths that may be prevented by a certain vaccination. It is even possible to evaluate the epidemiologic trend of a disease and to calculate or estimate the point of time when the risks of disease and vaccination are just balanced, ie, when a vaccination has lost its beneficial effect. Vaccinations against measles, poliomyelitis and tick borne encephalitis in Austria are highly beneficial. BCG vaccination is still beneficial on a low level in Austria as far as protection against tuberculosis is concerned. This effect will persist for the rest of this century. The benefit of pertussis vaccination depends on the local epidemiologic situation. It has expired for non-risk groups in Austria since 1976 but continues to persist in the US.

Vaccine-drug interactions

Interaction between a vaccine and a drug has been reported only with influenza vaccine and four drugs (aminopyrine, phenytoin sodium, theophylline, and warfarin sodium), and with BCG vaccine and theophylline. Some of these interactions still are unconfirmed. The underlying mechanism of the interaction is thought to be due to the vaccine (as an interferon-inducer) inactivating the hepatic cytochrome P-450 system; this results in depressed drug metabolism and reduced clearance. Because this is a nonspecific mechanism it could occur with other vaccines and it is possible that other vaccine-drug interactions are unrecognized. The clinical significance of vaccine-drug interactions is not fully determined; available evidence suggests that adverse reactions to warfarin or theophylline are rare after influenza vaccination and their possibility should not deter physicians from vaccinating those elderly patients at risk from influenza. Physicians should, however, monitor the response of these patients to medication in the immediate period following vaccination in case an adverse reaction occurs.

Bordetella pertussis whole cell vaccines--efficacy and toxicity

The literature concerning efficacy and side effects of pertussis vaccines is reviewed. With few exceptions, most vaccines induce a protective immunity lasting for 2 to 5 years. The large-scale use of pertussis vaccines has markedly contributed to the decrease in pertussis morbidity in small children but in some countries the incidence has increased in older children. Not even countries with immunisation rates of 90-95% have managed to eradicate pertussis or prevent disease in infants below the age of immunisation. The pertussis-associated mortality is currently very low in the industrialised countries and no differences can be discerned when countries with high, low and zero immunisation rates are compared. Local and benign systemic reactions are commonly seen after immunisation. The vaccines also sometimes cause convulsions, a shock-like state and, rarely, serious neurological reactions.

Development of a pertussis component vaccine in Japan

Antibodies against two physicochemically purified haemagglutinins (HAs) of Bordetella pertussis (filamentous HA and leucocytosis-promoting-factor HA) protect laboratory animals from pertussis. A vaccine containing these two HAs was prepared and tested in trials involving about 5000 children. Culture supernatant of Bordetella pertussis, phase I, was treated with ammonium sulphate, and a crude extract of the HAs was extracted from the precipitate by the use of concentrated sodium chloride. This crude extract was fractionated by sucrose density gradient centrifugation to obtain an HA preparation practically free of endotoxin. The HA preparation was treated with formalin to destroy its ability to induce leucocytosis and to cause histamine sensitisation. Aluminium hydroxide was added to the preparation as an adjuvant. The component vaccine is not only potent as judged by the mouse test but is also less than one-tenth as toxic as whole-cell vaccine as judged by leucocytosis promotion, histamine sensitisation, and endotoxicity tests. Field trials showed that component vaccine was as effective as and produced less side-effects than did conventional whole-cell vaccine. The vaccine has been used for mass immunisation in Japan since the autumn of 1981.

Whooping cough vaccination: a review of the controversy since the 1981 DHSS report

This article reviews the literature on the whooping cough controversy subsequent to the publication of the DHSS report in 1981. The report's reception is outlined and its influence on specific, topical issues such as contraindications, vaccine efficacy, and the calculation of 'risk' statistics is considered. The seriousness of the disease, the age of its victims and its treatment by antibiotics are also discussed with specific reference to recent epidemics. The implications of recent research findings for the continuation of the immunization programme are presented. It is concluded that the controversy continues.

Status of antitoxic immunity against diphtheria in Japan. A report of the National Epidemiological Surveillance for Important Communicable Diseases

Antitoxic immunity against diphtheria was surveyed during the period from 1962 to 1980. The survey was done by Schick test in the first decade and then by antitoxin titration of sera by the cell culture method in the recent six years. The data show clearly that the successful control of diphtheria has been accomplished in Japan as the result of active immunization. Both single (D) and combined (DP or DPT) vaccines were effective to convert Schick reaction negative. In addition, immunity was greatly improved by the introduction of the combined vaccine and one additional booster injection. However, such subsequent changes in the immunization schedule introduced in 1976 that giving the primary vaccination at older age and the omission of one booster injection at the preschool, has resulted in appearance of a high risk group below three years of age as well as in the lower immunity levels among school children. The data indicate that the continuous surveillance for diphtheria is required in this country.