Vaccination in special situations.

OBJECTIVE To review the indications, contraindications and efficacy of vaccination in some special situations: immunosuppression, prematurity, pregnancy and post-exposure situations. SOURCES OF DATA Systematic review of articles published during the two last decades, found in MEDLINE, SciELO and Lilacs databases; guidelines of Programa Nacional de Imunizações (Brazilian National Immunization Program), 2001 to 2004, and of Programa Nacional de DST/AIDS (Brazilian National STD/AIDS Program), 2004. Abstracts published in national and international pediatric and infectious disease congress annals during the last five years were also consulted. SUMMARY OF THE FINDINGS Some special situations, such as immunosuppression, prematurity, pregnancy and exposure to infectious diseases increased the risk of diseases or adverse post-vaccination events. In these situations, special vaccines or special vaccination schedules are indicated, or vaccines should be postponed or even forbidden. In general, toxoid or inactivated vaccines can be used, considering the possibility of insufficient immune response. For immunosuppressed patients, in accordance with the type of immunosuppression, live virus or bacterial vaccines should be avoided, because of the risk of vaccine agent spread. Immunization should include not only the patient, but his/her home and day-care contacts as well. CONCLUSIONS Knowledge about the schedule indicated for each situation improves the chances of better vaccine protection and decreases the risk of adverse events. Immunosuppressed or immunodeficient patients whose post-vaccine antibody titers are not available should be considered susceptible when exposed to infectious disease, and all the available prophylactic measures should be implemented, even when the vaccination schedule is correct.