Typhoid vaccination – Update

T WO ‘NEW’ TY PHOID VAC CINES ARE NOW AVAIL ABLE FOR USE in Can ada: an oral live at tenu ated vac cine (Vivo tif Berna vac cine), manu fac tured from the Ty21a strain of Sal mo nella ty phi by the Swiss Se rum and Vac cine In sti tute; and a cap su lar poly sac cha ride vac cine (VICPS) for par enteral use (Ty phim Vi) manu fac tured by Pas teur Mé rieux (1). Sev eral field tri als con ducted among in dige nous chil dren and adults in dis ease en demic ar eas have shown both vac cines to have an ef fi cacy of ap proxi mately 70%, no bet ter than that of the par enteral whole cell in ac ti vated vac cine that is no longer avail able (2-5). How ever, the ef fi cacy of these new vac cines has not been stud ied among per sons from ar eas with out en demic ty phoid fe ver who travel to dis ease en demic re gions. Both vac cines pro vide pro tec tive im mu nity within one week af ter com ple tion of the rec om mended dose(s). Ad verse re ac tions are rela tively low for both vac cines. Side ef fects with Ty21a are un com mon and con sist mainly of gas tro in tes ti nal up set and rash or ur ti caria (6). In sev eral tri als VICPS pro duced fe ver in fewer than 1% of vac ci nees, head ache in 1.5 to 3% and ery thema or in du ra tion of 1 cm or more at the in jec tion site in 7% of vac ci nees (5,7). The choice of vac cine will de pend on the age of the vac ci nee, du ra tion of pro tec tion, the un der ly ing health status (ie, im mu no com pro mised), the pre ferred route of ad mini stra tion and com pli ance is sues. The oral vac cine is rec om mended for those six years of age and older, whereas VICPS may be given to chil dren as young as two years. Booster doses for Ty21a are rec om mended every seven years com pared with three years (two years in the United States) for VICPS. Since Ty21a is a live at tenu ated vac cine it is not rec om mended for preg nant women or im mu no com pro mised per sons. The only con tra in di ca tion for VICPS is a his tory of se vere lo cal or sys temic re ac tions fol low ing a pre vi ous dose. Com pli ance and stor age is sues are a con sid era tion for the oral vac cine since it is selfadministered over eight days and must be re frig er ated at all times. The vac cine should not be used if it has been ex posed to tem pera tures above 26.8°C and/or sun light. How ever, re cent in for ma tion from the manu fac turer sug gests that vac cine ex po sure to tem pera tures be low 26.8°C for up to 48 h or freez ing the vac cine by mis take will not re duce its po tency. Ty21a should be ad min is tered 24 h or more af ter an an ti mi cro bial agent and 8 h af ter me flo quine. Chlo ro quine does not ap pear to af fect vac cine po tency. The de vel op ment of two new vac cines for ty phoid fe ver has been a sig nifi cant im prove ment over pre vi ous prepa ra tions be cause of longer du ra tion of pro tec tion, the avail abil ity of an oral vac cine and the lower in ci dence of ad verse re ac tions. These vac cines are in di cated for trav el lers to en demic ar eas (par ticu larly Asia, Af rica and Latin Amer ica) who plan to live with fam ily, stay for long pe ri ods (longer than one month) or who travel off the usual tour ist routes, es pe cially when ac cess to safe food and wa ter can not be guar an teed (8,9). How ever, since nei ther vac cine is 100% pro tec tive, trav el lers must be cau tioned about the need to take hy gi enic pre cau tions with re spect to food and drink. As a cor ol lary, those who care for ill re turn ing trav el lers must re mem ber to con sider ty phoid fe ver in the dif fer en tial di ag no sis of feb rile re turned trav el lers even if they have been im mu nized against the in fec tion.

T WO 'NEW' TY PHOID VAC CINES ARE NOW AVAIL ABLE FOR USE in Can ada: an oral live at tenu ated vac cine (Vivo tif Berna vac cine), manu fac tured from the Ty21a strain of Sal mo nella ty phi by the Swiss Se rum and Vac cine In sti tute; and a cap sular poly sac cha ride vac cine (VICPS) for par enteral use (Ty phim Vi) manu fac tured by Pas teur Mé rieux (1). Sev eral field tri als con ducted among in dige nous chil dren and adults in dis ease en demic ar eas have shown both vac cines to have an ef fi cacy of ap proxi mately 70%, no bet ter than that of the par enteral whole cell in ac ti vated vac cine that is no longer avail able (2)(3)(4)(5). How ever, the ef fi cacy of these new vac cines has not been stud ied among per sons from ar eas with out en demic ty phoid fe ver who travel to dis ease en demic re gions. Both vac cines pro vide pro tec tive im mu nity within one week af ter com ple tion of the rec om mended dose(s).
Ad verse re ac tions are rela tively low for both vac cines. Side ef fects with Ty21a are un com mon and con sist mainly of gas tro in tes ti nal up set and rash or ur ti caria (6). In sev eral tri als VICPS pro duced fe ver in fewer than 1% of vac ci nees, headache in 1.5 to 3% and ery thema or in du ra tion of 1 cm or more at the in jec tion site in 7% of vac ci nees (5,7).
The choice of vac cine will de pend on the age of the vac cinee, du ra tion of pro tec tion, the un der ly ing health status (ie, im mu no com pro mised), the pre ferred route of ad mini stra tion and com pli ance is sues. The oral vac cine is rec om mended for those six years of age and older, whereas VICPS may be given to chil dren as young as two years. Booster doses for Ty21a are rec om mended every seven years com pared with three years (two years in the United States) for VICPS. Since Ty21a is a live at tenu ated vac cine it is not rec om mended for pregnant women or im mu no com pro mised per sons. The only contra in di ca tion for VICPS is a his tory of se vere lo cal or sys temic re ac tions fol low ing a pre vi ous dose.
Com pli ance and stor age is sues are a con sid era tion for the oral vac cine since it is self-administered over eight days and must be re frig er ated at all times. The vac cine should not be used if it has been ex posed to tem pera tures above 26.8°C and/or sun light. How ever, re cent in for ma tion from the manufac turer sug gests that vac cine ex po sure to tem pera tures below 26.8°C for up to 48 h or freez ing the vac cine by mis take will not re duce its po tency. Ty21a should be ad min is tered 24 h or more af ter an an ti mi cro bial agent and 8 h af ter me floquine. Chlo ro quine does not ap pear to af fect vac cine potency.
The de vel op ment of two new vac cines for ty phoid fe ver has been a sig nifi cant im prove ment over pre vi ous prepa rations be cause of longer du ra tion of pro tec tion, the avail abil ity of an oral vac cine and the lower in ci dence of ad verse re actions. These vac cines are in di cated for trav el lers to en demic ar eas (par ticu larly Asia, Af rica and Latin Amer ica) who plan to live with fam ily, stay for long pe ri ods (longer than one month) or who travel off the usual tour ist routes, es pe cially when access to safe food and wa ter can not be guar an teed (8,9). However, since nei ther vac cine is 100% pro tec tive, trav el lers must be cau tioned about the need to take hy gi enic pre cau tions with re spect to food and drink. As a cor ol lary, those who care for ill re turn ing trav el lers must re mem ber to con sider ty phoid fe ver in the dif fer en tial di ag no sis of feb rile re turned trav el lers even if they have been im mu nized against the in fec tion.

JS Key stone MD Tropi cal Dis ease Unit The To ronto Hos pi tal
To ronto, On tario