The Use of Bacille Calmette-Guérin vaccination in Children

A THE IN FEC TIOUS ETI OL OGY OF TU BER CU LO SIS WAS de ter mined over a cen tury ago, a highly ef fec tive strat egy for pre vent ing this ageold dis ease has been elu sive. Rob ert Koch, af ter iden ti fy ing the eti ol ogy of tu ber cu lo sis, tried and failed to pro duce an ef fec tive vac cine; his ef forts dis graced him and nearly ru ined his ca reer. Sub se quently, the Ba cille CalmetteGuérin (BCG) vac cine was de vel oped by at tenu at ing a strain of My co bac te rium bo vis, and it has been in wide use since 1921 (1). Whereas BCG is the old est vac cine in use to day, its ef fi cacy has been im per fect. With the re cent emer gence of in fec tions with mul ti ply antibioticresistant strains of My co bac te rium tu ber cu lo sis and the risk of over whelm ing dis ease in pa tients with AIDS, re newed at ten tion has been fo cused on op ti miz ing pre ven ta tive strate gies. These In fec tious Dis ease Notes briefly sum ma rize the cur rent state of knowl edge about BCG and pro vide rec om men da tions for the use of BCG in chil dren. BCG was de rived by mul ti ple in vi tro pas sages of M bo vis. The vac cine has been dis trib uted world wide, and its ef fi cacy, which has been re ported to vary from 0 to 80% (1,2), may vary from one prepa ra tion to an other (2). A re cent metaanalysis with a sub set analy sis of new born and in fant im mu ni za tion dem on strated that the over all pro tec tive rate is about 50%, with 71% pro tec tion against death and 64% against men in gi tis (3,4). The rea son for the wide varia tion in es ti mates of pro tec tive ness among stud ies has been hotly de bated, but ap pears to be re lated to the geo graphi cal lati tude of the re cipi ent and to the in ci dence of tu ber cu lo sis in the tar get group (5). Whereas BCG vac ci na tion has been in sti tuted glob ally for about 75 years, many con cerns about its use per sist. Its ef fi cacy is far be low what is ex pected of other widely used vac cines, such as those for pre ven tion of oral po lio mye li tis or Hae mo phi lus in flu en zae type b. No method is avail able for as sess ing pro tec tive im mu nity: skin test re ac tiv ity to pu ri fied pro tein de riva tive (PPD) of tu ber cu lin is no to ri ously un re li able; the du ra tion of pro tec tion fol low ing BCG ad mini stra tion is un known; and its ad mini stra tion elimi nates the util ity of skin test ing with PPD for the di ag no sis of tu ber cu lo sis. Further more, since it is a live bac te rial vac cine, it is contra in di cated in im mu no de fi cient in di vidu als (par ticu larly those with de fects in cellmediated im mu nity), and in peo ple with ex ten sive ther mal in jury or other se ri ous skin dis eases. Mild ad verse ef fects in clud ing ul cera tion at the site of in ocu la tion, mus cle sore ness and re gional lym pha de ni tis are com mon. More se ri ous com pli ca tions in clud ing dis semi na tion in im mu no com pro mised hosts (such as in fants with se vere com bined im mu no de fi ciency) and os tei tis are rare. Op ti mal con trol of tu ber cu lo sis re quires a multifac eted ap proach, in which vac ci na tion is but one com po nent. Other criti cal meas ures in clude early iden ti fi ca tion and treat ment of ac tive cases, use of pre ven ta tive che mo ther apy in those with in ac tive in fec tion and the in sti tu tion of ag gres sive in fec tion con trol meas ures in en vi ron ments where the or gan ism is likely to spread, such as hos pi tals and resi den tial com mu ni ties. BCG vac ci na tion should be con sid ered only when ex po sure to tu ber cu lo sis is un avoid able and when other in fec tion con trol meas ures are un likely to suc ceed in pre vent ing new cases. Since in fants and chil dren are at par ticu larly high risk of de vel op ing ex trapul mon ary tu ber cu lo sis, they are natu ral can di dates for BCG vac ci na tion if their ex po sure to oth ers with ac tive dis ease is un avoid able. Fur ther more, BCG only has to be given once and it may be ad min is tered at any time (in clud ing the neo na tal pe riod). BCG vac ci na tion of in fants and chil dren should be lim ited to cer tain high risk groups (such as abo rigi nal Ca na di ans liv ing on re serves [6]) and is rec om mended for the fol low ing (7):