evidence: Haemophilus influenzae type b capsular polysaccharide vaccine in children: a double-blind field study of 100,000 vaccinees 3 months to 5 years of age in Finland - PMID: 335348 Haemophilus influenzae type b capsular polysaccharide vaccine in children: a double-blind field study of 100,000 vaccinees 3 months to 5 years of age in Finland [...] A randomized, prospective field trial of a conjugate vaccine in the protection of infants and young children against invasive Haemophilus influenzae type b disease.N Engl J Med. 1990 Nov 15;323(20):1381-7. doi: 10.1056/NEJM199011153232004. N Engl J Med. 1990. PMID: 2233904 Clinical Trial.