Sensibilidade tuberculínica pós-vacinal e sua irrelevância para a revacinação BCG

Abstract

INTRODUÇÃOA observação de que apenas uma pequena parcela das pessoas infectadas pelo bacilo de Koch apresenta manifestações clínicas da tuberculose doença, remonta ao começo deste século. A maioria dos infectados parecia haver adquirido com a infecção uma certa resistência a novas infecções. Essa impressão inicial se transformou em certeza depois que estudos epidemiológicos demonstraram que a incidência da doença era significativamente menor entre os reatores à tuberculina do que entre os não-reatores, quando submetidos a condições de contágio intenso 10,21,23,32 ; em outras palavras, o estado de infectado expresso pela alergia tuberculínica acompanhava-se de maior resistência a novas infecções, em comparação com o estado de não-infectado.Sabia-se, também, desde o início do século, que os anticorpos do soro desempenham numerosas e importantes funções protetoras contra infecções. Havia, entre-

Vacina BCG: via percutânea ou intradérmica?

“…6,10,18,19 The Moureau-Rio de Janeiro strain that is employed in Brazil induces a good delayed type hypersensitivity (DTH) skin test response and rarely causes local or systemic adverse reactions. 3,18,[20][21][22][23][24][25][26] A study of 132 Brazilian neonates recorded just 12 local reactions (0.9%), four (0.3%) of which were suppurating adenites, six (0.45%) prolonged ulcers, and two (0.15%) lupoid reactions. 18 In South Africa, the rate of occurrence of local reactions after BCG-ID use was 3% of 9,763 newborn babies.…”

“…When the vaccine is administered more than 8 hours after preparation, DTH skin test response is reduced and scars are formed over a smaller area than when the vaccine is used less than eight hours after preparation. 18 In Brazil, the majority of children vaccinated with BCG-ID exhibit scarring, [20][21][22][23][24][25][26] and it is recommended that those who do not exhibit any local reaction within six months be re-vaccinated. 3,17 While this method is highly useful, in practice scar reading is not always reliable.…”

“…30 The Moureau-Rio de Janeiro strain used in Brazil is highly immunogenic, both in school-age children and infants, although among infants, the vaccine induces less DTH skin test response stimulation. 3,17,[21][22][23][24][25]37 There are large variations between individuals in terms of DTH skin test response and, if tuberculin testing is repeated, some individuals exhibit reversal of previous results while others return the same results as at first testing. 21 The reliability of cutaneous testing is not always good; in up to 5% of cases a second DTH skin test response made by the same observer will lead to a reversal of the previous classification.…”

“…3,17,[21][22][23][24][25]37 There are large variations between individuals in terms of DTH skin test response and, if tuberculin testing is repeated, some individuals exhibit reversal of previous results while others return the same results as at first testing. 21 The reliability of cutaneous testing is not always good; in up to 5% of cases a second DTH skin test response made by the same observer will lead to a reversal of the previous classification. 45 Furthermore, over time, the response to tuberculin testing diminishes, although, if there is exposure to M. tuberculosis or other mycobacteria, DTH skin test response will normally increase again.…”

“…45 Furthermore, over time, the response to tuberculin testing diminishes, although, if there is exposure to M. tuberculosis or other mycobacteria, DTH skin test response will normally increase again. 21,46 While DTH skin test response has been much used in research to assess the response to BCG vaccination, this test is not considered an accurate marker for immunity. Studies performed on experimental animals and on humans demonstrated that DTH skin test response has no relationship with protection and that individuals who react strongly to PPD may be less well protected against tuberculosis compared to those who do not exhibit a positive DTH skin test response.…”