Pasteur had the genius to establish, among many other "firsts", tissue culture as a method to seek a solution to minimize the morbidity of a "virus" (from Sanscrit viras implying contagion and not feminine). Viral orgnanisms remained invisible until the era of molecular biology. Still, their nature and role in evolution (nothing make sense in Biology outside the light cast by evolution) continue to challenge many current dogmas in Biology ("mad cow" disease for example).
An imploring mother of a boy badly bitten by a rabid animal and facing certain death induced Pasteur to treat him with a never tested before vaccine on humans. Pasteur upheld the view that science had to have a "human face" and rejected the notion that there is a "basic" and "applied" sorts of scientific pursuits. For Pasteur, science was one because its sole purpose was humanism.
The boy lived ... years later, as a adult, he surrendered his life to preserve the dignity of the tomb of Pasteur (he was the custodian of the Pasteur Institute and apparently chose suicide rather than follow orders by Nazi occupation authorities to unseal the crypt).