G Model
ARTICLE IN PRESS
JVAC-15400; No. of Pages 1
Vaccine xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Vaccine journal homepage: www.elsevier.com/locate/vaccine
Letter to the Editor Response on letter by Arya et al.: “Evaluation of immune responses to an oral typhoid vaccine, Ty21a, in children from 2 to 5 years of age in Bangladesh.” Letter by Arya et al. is encouraging since an effective vaccine is needed for protection against typhoid fever especially in developing countries. In recent times the prevalence of the disease is increasing and is being documented increasingly in young children. More than one-fourth (27%) of typhoid cases are shown to occur in children under 2 years of age and in infants [1–3]. Hence a vaccine is greatly needed for this age group as it is for older children and adults. In our original article [4], we have concluded that the oral typhoid Ty21a vaccine is safe and immunogenic in children, 2–5 years of age when given in a liquid formulation. Based on this, we suggest that a liquid formulation of Ty21a should be tested in younger age groups as well. There are two licensed vaccines for typhoid fever now available. The oral Ty21a vaccine is registered for use by children 6 years and above and the parenteral Vi polysaccharide vaccine in those older than two years of age. There are new Vi conjugate vaccines now being formulated will hopefully be immunogenic in very young children [5]. However, until the availability of such vaccines, studies on the liquid formulation of the oral Ty21a vaccine in young children 9 months to 5 years of age in phase III trial needs to be conducted as soon as possible. Once proven efficacious, the vaccine can be used as a public health tool for prevention of typhoid fever in different endemic countries of typhoid fever, including Bangladesh. The Ty21a live oral vaccine also has been found to be protective against disease caused by S. Paratyphi B [6] and this may turn to be an added advantage of the vaccine since the incidence of both typhoid and paratyphoid fever is increasing globally. One important goal is to have an oral typhoid vaccine that is useful for children down to 9 months of age so it could be given at the same time as the EPI schedule of vaccines are given. It would also be most practical if the vaccine could be given as a single dose. In an attempt to determine an optimal dose and schedule, several studies can be carried out to move down to the target age group and to find a dose which is most practical while maintaining immunogenicity and protective efficacy.
References [1] Levine MM, Taylor DN, Ferreccio C. Typhoid vaccines come of age. Pediatr Infect Dis J 1989;8:374–81. [2] Saha SK, Baqui AH, Hanif M, Darmstadt GL, Ruhulamin M, Nagatake T, et al. Typhoid fever in Bangladesh: implications for vaccination policy. Pediatr Infect Dis J 2001;20:521–4. [3] Walsh AL, Phiri AJ, Graham SM, Molyneux EM, Molyneux ME. Bacteremia in febrile Malawian children: clinical and microbiologic features. Pediatr Infect Dis J 2000;19:312–8. [4] Bhuiyan TR, Choudhury FK, Khanam F, Saha A, Sayeed MA, Salma U, et al. Evaluation of immune responses to an oral typhoid vaccine, Ty21a, in children from 2 to 5 years of age in Bangladesh. Vaccine 2014;32:1055–60. [5] Szu SC. Development of Vi conjugate – a new generation of typhoid vaccine. Expert Rev Vaccines 2013;12:1273–86. [6] Levine MM, Ferreccio C, Black RE, Lagos R, San Martin O, Blackwelder WC. Ty21a live oral typhoid vaccine and prevention of paratyphoid fever caused by Salmonella enterica Serovar Paratyphi B. Clin Infect Dis 2007;45(Suppl. 1):S24–8.
Taufiqur R. Bhuiyan Feroza K. Choudhury Farhana Khanam Amit Saha Md. Abu Sayeed Umme Salma Firdausi Qadri ∗ Centre for Vaccine Sciences, International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh Anna Lundgren Ann-Mari Svennerholm Department of Microbiology and Immunology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden David A. Sack Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA ∗ Corresponding
author. Tel.: +880 2 9827001 10x2431; fax: +880 2 8823116. E-mail address: [email protected] (F. Qadri) 26 March 2014 Available online xxx
http://dx.doi.org/10.1016/j.vaccine.2014.03.099 0264-410X/© 2014 Published by Elsevier Ltd.
Please cite this article in press as: Bhuiyan TR, et al. Response on letter by Arya et al.: “Evaluation of immune responses to an oral typhoid vaccine, Ty21a, in children from 2 to 5 years of age in Bangladesh.”. Vaccine (2014), http://dx.doi.org/10.1016/j.vaccine.2014.03.099
ARTICLE IN PRESS
JVAC-15400; No. of Pages 1
Vaccine xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Vaccine journal homepage: www.elsevier.com/locate/vaccine
Letter to the Editor Response on letter by Arya et al.: “Evaluation of immune responses to an oral typhoid vaccine, Ty21a, in children from 2 to 5 years of age in Bangladesh.” Letter by Arya et al. is encouraging since an effective vaccine is needed for protection against typhoid fever especially in developing countries. In recent times the prevalence of the disease is increasing and is being documented increasingly in young children. More than one-fourth (27%) of typhoid cases are shown to occur in children under 2 years of age and in infants [1–3]. Hence a vaccine is greatly needed for this age group as it is for older children and adults. In our original article [4], we have concluded that the oral typhoid Ty21a vaccine is safe and immunogenic in children, 2–5 years of age when given in a liquid formulation. Based on this, we suggest that a liquid formulation of Ty21a should be tested in younger age groups as well. There are two licensed vaccines for typhoid fever now available. The oral Ty21a vaccine is registered for use by children 6 years and above and the parenteral Vi polysaccharide vaccine in those older than two years of age. There are new Vi conjugate vaccines now being formulated will hopefully be immunogenic in very young children [5]. However, until the availability of such vaccines, studies on the liquid formulation of the oral Ty21a vaccine in young children 9 months to 5 years of age in phase III trial needs to be conducted as soon as possible. Once proven efficacious, the vaccine can be used as a public health tool for prevention of typhoid fever in different endemic countries of typhoid fever, including Bangladesh. The Ty21a live oral vaccine also has been found to be protective against disease caused by S. Paratyphi B [6] and this may turn to be an added advantage of the vaccine since the incidence of both typhoid and paratyphoid fever is increasing globally. One important goal is to have an oral typhoid vaccine that is useful for children down to 9 months of age so it could be given at the same time as the EPI schedule of vaccines are given. It would also be most practical if the vaccine could be given as a single dose. In an attempt to determine an optimal dose and schedule, several studies can be carried out to move down to the target age group and to find a dose which is most practical while maintaining immunogenicity and protective efficacy.
References [1] Levine MM, Taylor DN, Ferreccio C. Typhoid vaccines come of age. Pediatr Infect Dis J 1989;8:374–81. [2] Saha SK, Baqui AH, Hanif M, Darmstadt GL, Ruhulamin M, Nagatake T, et al. Typhoid fever in Bangladesh: implications for vaccination policy. Pediatr Infect Dis J 2001;20:521–4. [3] Walsh AL, Phiri AJ, Graham SM, Molyneux EM, Molyneux ME. Bacteremia in febrile Malawian children: clinical and microbiologic features. Pediatr Infect Dis J 2000;19:312–8. [4] Bhuiyan TR, Choudhury FK, Khanam F, Saha A, Sayeed MA, Salma U, et al. Evaluation of immune responses to an oral typhoid vaccine, Ty21a, in children from 2 to 5 years of age in Bangladesh. Vaccine 2014;32:1055–60. [5] Szu SC. Development of Vi conjugate – a new generation of typhoid vaccine. Expert Rev Vaccines 2013;12:1273–86. [6] Levine MM, Ferreccio C, Black RE, Lagos R, San Martin O, Blackwelder WC. Ty21a live oral typhoid vaccine and prevention of paratyphoid fever caused by Salmonella enterica Serovar Paratyphi B. Clin Infect Dis 2007;45(Suppl. 1):S24–8.
Taufiqur R. Bhuiyan Feroza K. Choudhury Farhana Khanam Amit Saha Md. Abu Sayeed Umme Salma Firdausi Qadri ∗ Centre for Vaccine Sciences, International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka, Bangladesh Anna Lundgren Ann-Mari Svennerholm Department of Microbiology and Immunology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden David A. Sack Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA ∗ Corresponding
author. Tel.: +880 2 9827001 10x2431; fax: +880 2 8823116. E-mail address: [email protected] (F. Qadri) 26 March 2014 Available online xxx
http://dx.doi.org/10.1016/j.vaccine.2014.03.099 0264-410X/© 2014 Published by Elsevier Ltd.
Please cite this article in press as: Bhuiyan TR, et al. Response on letter by Arya et al.: “Evaluation of immune responses to an oral typhoid vaccine, Ty21a, in children from 2 to 5 years of age in Bangladesh.”. Vaccine (2014), http://dx.doi.org/10.1016/j.vaccine.2014.03.099
