Safety and Immunogenicity of Peru-15 Vaccine When Given With Measles Vaccine in Healthy Indian and Bangladeshi Infants
Safety and Immunogenicity of Peru-15 Vaccine When Given With Measles Vaccine in Healthy Indian and Bangladeshi Infants
The purpose of this study is to confirm the safety and immunogenicity of Peru-15 vaccine in
 infants when given simultaneously with measles vaccine.
Cholera is an important public health problem worldwide, remaining endemic in most of the
 developing world at the same time causing outbreaks in areas where lapses in sanitation
 occur. In 2005, 131 943 cholera cases and 2272 deaths were reported to the World Health
 Organization (WHO) with more countries reporting cholera outbreaks. Overall, this represents
 a 30% increase in the number of cases reported compared to 2004. The cholera case fatality
 rate during that year was 1.72%; however, recent outbreaks in West Africa resulted in
 case-fatality rates of as high as 12% [1, 2]. These figures are believed to be underestimates
 and that as much as 120 000 deaths due to cholera are estimated to occur each year [3]. Aside
 from this high mortality, cholera outbreaks cause economic and social disruptions.

 The states of West Bengal in India together with neighboring Bangladesh have been considered
 by many as the "homeland of cholera". In India, 4695 cases of cholera were reported to the
 WHO [1] with states such as West Bengal, Maharashtra, Andra Pradesh, Tamil Nadu, Karnataka
 and Delhi long been reporting outbreaks [4]. Although no country-wide data is available from
 Bangladesh, a 4 - year surveillance in 4 different geographical areas in Bangladesh reveal
 that cholera is widely distributed even in an area with no reported outbreaks for 10 years
 [5]. Cholera in these 2 countries affects all age groups, with the youngest age group being
 the most affected. In Kolkata, children <5 years of age had a 30% higher risk of having
 cholera compared to older individuals [6] and in Bangladesh, 53% of 5670 cholera-infected
 patients in the 4-year surveillance were children <5 years of age [5]. Further analysis of a
 3 year prospective surveillance of cholera in Kolkata shows that infants less than 2 years of
 age had a cholera incidence rate of 4.20 per 1000 person-years whereas the over-all rate in
 the study population was 1.41 per 1000 person-years (Data on file).

 Provision of safe water and food, establishment of adequate sanitation, and implementation of
 personal and community hygiene constitute the main public health interventions against
 cholera. These measures cannot be fully implemented in the near future in most
 cholera-endemic areas. A safe, effective, and affordable vaccine would be a useful tool for
 cholera prevention and control.

 Considerable progress has been made during the last decade in the development of new
 generation oral vaccines against cholera. These have already been licensed in some countries
 and are now being considered for wider public health application. The World Health
 Organization recently recommended that the newer generation cholera vaccines be considered in
 certain endemic and epidemic situations, but indicated that demonstration projects are needed
 to provide more information about the costs, feasibility, and impact of using these vaccines
 [7].

 A killed oral cholera vaccine (Dukoral™) has long been available internationally, however its
 2-dose schedule, the use of a buffer and the cost of the vaccine have impeded its use in
 public health settings. A live oral vaccine, CVD-103 HgR (Orochol™), although internationally
 licensed is currently not available in the market. This vaccine is only available for use in
 children older than 6 years old and adults. Despite the immunogenicity and efficacy in
 challenge studies in North American volunteers [8], in a field trial of this vaccine in an
 endemic area in Indonesia, no protective efficacy was detected during the period of
 observation [9].

 A need exists for an improved cholera vaccine that is more thermostable and may be used in
 endemic countries in younger age groups. This new generation oral cholera vaccine must be
 administered in a single-dose regimen, be thermostable, confer high grade long-term
 protection and may be given to children below 2 years of age through mass immunization
 campaigns or through the expanded programme on immunization (EPI). In the Diseases of the
 Most Impoverished Programme (DOMI) of the IVI, Peru-15 was identified as the most promising
 of all the vaccine candidates. It is a live oral attenuated cholera vaccine derived from V.
 cholerae O1 El Tor Inaba strain that was first isolated in Peru in 1991 [10]. This has the
 advantage of being given in a single dose and of having the same biotype as the current
 pandemic strain (biotype El tor), unlike CVD-103 HgR which is a classical biotype. Peru-15
 has been attenuated by several genetic modifications and deletions. By the deletion of the
 ctx A and the rtxA genes, it has been rendered unable to encode for cholera toxin subunit A
 and RTX toxin making it non-toxigenic and by insertion of the cholera toxin B gene to the
 recA gene, it enabled the strain to produce cholera toxin B. This insertion has inactivated
 the recA gene, and this together with the deletion of the attRS1 sequences, has decreased the
 ability of the strain to integrate exogenous DNA making it non-recombinational. Lastly, by
 the absence of the potentially inflammatory flagella it has been rendered non-motile [10,
 11]. In addition, Phase I and II studies have been performed in North American volunteers
 where it was found to be safe and immunogenic [11-12]. Furthermore, the vaccine strain
 isolated from the stools of volunteers retained its non-motile characteristic. In a challenge
 study among North American volunteers, Peru-15 provided 100% protection against moderate and
 severe diarrhoea, and 93% against any diarrhoea [13].

 This vaccine underwent phase I and II studies in a cholera-endemic area in Dhaka, Bangladesh
 in three age groups: adults aged 18 - 45 years, children aged 2 - 5 years and infants aged 9
 - 23 months [14, 15]. In these studies, a 2 x108 CFU dose of the vaccine was shown to be safe
 and able to elicit vibriocidal responses among all age groups. 75% of adults, 84% of children
 aged 2-5 years and 70% of infants aged 9-23 months developed a 4-fold rise from baseline in
 their vibriocidal titres. Only 1 of 20 adults and 8 of 140 children who received vaccine
 excreted the vaccine strain up to 4 days after vaccination. Analysis of the strains isolated
 revealed that the strains remained unchanged in phenotypic and genotypic properties after
 passage in the stool.

 To date, the vaccine has been tested on more than 400 volunteers. The freshly harvested
 product, tested on 23 volunteers and the frozen lyophilized preparation, tested on 381
 volunteers were both shown to be safe and immunogenic in all age groups. The most frequently
 reported adverse events were gastrointestinal symptoms (diarrhea, nausea, abdominal cramping,
 gas, decreased appetite) and headache and in controlled studies were reported in similar
 frequencies in subjects who received Peru-15 and placebo. The optimal dose for healthy adult
 travelers was a single, oral dose of 1 x 108 CFU. The study in Bangladesh further confirmed
 that a 108 dose was safe and immunogenic in all age groups including infants among residents
 of a cholera endemic area.

 Avant Immunotherapeutics Inc., manufacturers of Peru-15, are in the process of reformulating
 the vaccine with the long-term stabilizing ability of trehalose in order to make Peru-15 more
 thermostable at elevated temperatures, i.e. 2-8ºC. If this reformulation is proven as safe
 and at least as immunogenic as the previous version, then this will make vaccine storage
 easier and more easily deployable in field conditions in Africa, in refugee settings and in
 endemic countries in South Asia.

 The International Vaccine Institute (IVI) through the Cholera Vaccine Initiative (CHOVI)
 together with Avant Immunotherapeutics Inc., manufacturers of the Peru-15 vaccine, have
 negotiated an agreement that allow clinical trials on this reformulated vaccine to be
 performed in 2 cholera-endemic countries - India and Bangladesh. This will eventually enable
 licensure and facilitate the international use of this vaccine by obtaining a WHO
 recommendation for its global use. This single dose vaccine may easily be used in endemic
 countries and deployed at times when outbreaks are likely to occur. Furthermore, this vaccine
 may potentially be used in infants and young children who have the highest risk of cholera,
 potentially being included as part of the EPI in endemic areas.

 The previous formulations of the vaccine were shown to be safe and immunogenic in all age
 groups, including infants, in a cholera endemic area [12 - 15] and efficacious in preventing
 cholera diarrhea in healthy adult volunteers [13]. In view of this, the current dose of up to
 109 of the current formulation will be directly tested among infants.Data regarding the
 safety and immunogenicity of the trehalose-reformulated Peru-15 vaccine among infants need to
 be confirmed in order to pave the way for the possible use of this vaccine in cholera-endemic
 areas where infants and children are most at risk. Furthermore, if this vaccine will be used
 in the context of the EPI to be given together with measles vaccine, it would be important to
 determine if immune interference exists between these 2 live attenuated vaccines.
Inclusion Criteria:

 Healthy male and female infants aged 9 - 12 months will be recruited from Vellore, India
 and Dhaka, Bangladesh.

 All subjects must satisfy the following criteria at study entry:

 1. Male or female infants aged 9 - 12 months whose parents or primary caretaker have
 given the written informed consent prior to study entry

 2. Will comply with the requirements of the protocol (i.e. available for follow-up visits
 and specimen collection).

 3. Healthy subjects as determined by:

 -  Medical history

 -  Physical examination

 -  Clinical judgment of the investigator

 Exclusion Criteria:

 1. Parents or primary caregiver are unwilling or unable to give written informed consent
 to participate in the study

 2. Ongoing serious chronic disease

 3. Immunocompromising condition or therapy

 4. Abdominal pain or cramps, loss of appetite, nausea, general ill-feeling or vomiting in
 the past 24 hours

 5. Intake of any anti-diarrheal medicine in the past week

 6. Acute disease one week prior to enrollment, with or without fever. Temperature ≥38ºC
 (oral) or axillary temperature ≥ 37.5ºC warrants deferral of the vaccination pending
 recovery of the subject

 7. Receipt of antibiotics in the past 2 weeks

 8. Receipt of live or killed enteric vaccine in the last 4 weeks

 9. Diarrhea (3 or more loose stools within a 24-hour period) 6 weeks prior to enrollment

 10. One or two episodes of diarrhea lasting for more than 2 weeks in the past 6 months

 11. One or two episodes of abdominal pain lasting for more than 2 weeks in the past 6
 months

 12. Receipt of killed oral cholera vaccine

 13. Have previously received a dose of a measles-containing vaccine (MCV)

 14. Have previously presented with a disease potentially related to measles

 15. Receipt of blood, blood products or a parenteral immunoglobulin preparation in the
 previous 3 months

 16. History of anaphylaxis, any serious vaccine reaction, allergy to eggs, egg products or
 to any measles vaccine component

 17. any condition which in the opinion of the investigator, might interfere with the
 evaluation of the study objectives