Global Vaccine Safety

Isoniazid resistance of bacille Calmette-Guerin strains

Extract from report of GACVS meeting of 9-10 June 2005, published in the WHO Weekly Epidemiological Record on 15 July 2005

The recent isolation of strains of bacille Calmette–Guérin (BCG) resistant to isoniazid from 5 patients with lymphadenitis in the Netherlands has brought into question the clinical relevance of the finding and whether the use of isoniazid-resistant BCG vaccine should be discontinued. The Netherlands experience relates to the Danish 1331 strain of BCG, used in the Netherlands since 1998. It is well known that there is a certain degree of isoniazid resistance of isolated BCG strains.

The use of isoniazid as single drug treatment for BCG vaccine-induced lymphadenitis is recommended only in the Netherlands. Elsewhere, most cases of BCG lymphadenitis are managed either by doing nothing or by surgical excision if necessary. For disseminated infection in patients with immune deficiency, treatment with 3 or more anti-tuberculosis drugs is recommended. A distinction should be made between such cases and those with lymphadenitis arising as a frequent consequence of BCG vaccination. Even in countries with a high prevalence of human immunodeficiency virus (HIV) infection in newborn infants, lymphadenitis is regarded as having no clinical relevance provided the correct injection technique has been used and adverse reactions are adequately treated. The Committee concluded that the isolation and identification of a low level of isoniazid resistance of BCG strains from 5 patients presenting with lymphadenitis do not justify a change in standard policy.