除了發現防止紅酒變酸的方法之外，巴斯德也找到了導致蠶生病的原因。他的研究成果捍衛法國在絲織產業與時尚工業的優勢地位，這又是一樁足以令全法國人向他致敬的傑出成就。他接著將研究範圍拓展到家禽、家畜與人類疾病作用的方式，更透過研究疫苗證實其功效。巴斯德提出了預防接種措施，認為傳染病的微生物在特殊的培養之下可以減輕毒力，變成防病的疫苗。他於1881年著手研究狂犬病，1885年以減毒的方式（the method for attenuatio of virulent microorganisms）研製出減毒狂犬病疫苗，巴斯德的名聲引來大西洋彼岸的求助，當時美國新澤西幾名男童遭到感染狂犬病的犬隻攻擊，性命垂危。這起新聞引起美國民眾的重視，自發集資協助這幾名男童跨越大西洋至巴黎，尋求巴斯德的救助，而巴斯德也不負眾望，利用他研究出的狂犬病疫苗，在同年7月6日治療一受狂犬咬傷的9歲兒童Joseph Meister（英語：Joseph Meister）。[8]至此，巴斯德已經是跨越歐陸國界及大西洋隔閡的知識英雄。
莫里斯·瓦萊里-拉多（法語：Maurice Vallery-Radot）是巴斯德女婿兄弟的外孫，也是天主教徒。他也堅持巴斯德深信天主教。[20]有一個被巴斯德·瓦萊里-拉多和莫里斯·瓦萊里-拉多證明是假的所謂巴斯德的話：[21]"The more I know, the more nearly is my faith that of the Breton peasant. Could I but know all I would have the faith of a Breton peasant's wife".[4]根據莫里斯·瓦萊里-拉多，[22]這個錯誤的傳言最早是在巴斯德時候不久出現的。[23]
L. Pasteur (1848) "Mémoire sur la relation qui peut exister entre la forme cristalline et la composition chimique, et sur la cause de la polarisation rotatoire" (Memoir on the relationship which can exist between crystalline form and chemical composition, and on the cause of rotary polarization)," Comptes rendus de l'Académie des sciences (Paris), vol. 26, pages 535-538.
Pasteur Vallery-Radot, Letter to Paul Dupuy, 1939, quoted by Hilaire Cuny, Pasteur et le mystère de la vie, Paris, Seghers, 1963, p. 53–54. Patrice Pinet, Pasteur et la philosophie, Paris, 2005, p. 134–135, quotes analogous assertions of Pasteur Vallery-Radot, with references to Pasteur Vallery-Radot, Pasteur inconnu, p. 232, and André George, Pasteur, Paris, 1958, p. 187. According to Maurice Vallery-Radot (Pasteur, 1994, p. 378), the false quotation appeared for the first time in the Semaine religieuse .... du diocèse de Versailles, October 6, 1895, p. 153, shortly after the death of Pasteur.
Joseph McCabe. A Biographical Dictionary of Ancient, Medieval, and Modern Freethinkers. Haldeman-Julius Publications. 1945 [2012-08-11]. （原始內容存檔於2013-03-23）. The anonymous Catholic author quotes as his authority the standard biography by Vallery-Radot, yet this describes Pasteur as a freethinker; and this is confirmed in the preface to the English translation by Sir W. Osler, who knew Pasteur personally. Vallery-Radot was himself a Catholic yet admits that Pasteur believed only in "an Infinite" and "hoped" for a future life. Pasteur publicly stated this himself in his Academy speech in 1822 (in V.R.). He said: "The idea of God is a form of the idea of the Infinite whether it is called Brahma, Allah, Jehova, or Jesus." The biographer says that in his last days he turned to the Church but the only "evidence" he gives is that he liked to read the life of St. Vincent de Paul, and he admits that he did not receive the sacraments at death. Relatives put rosary beads in his hands, and the Catholic Encyclopedia claims him as a Catholic in virtue of the fact and of an anonymous and inconclusive statement about him. Wheeler says in his Dictionary of Freethinkers that in his prime Pasteur was Vice-President of the British Secular (Atheist) Union; and Wheeler was the chief Secularist writer of the time. The evidence is overwhelming. Yet the Catholic scientist Sir Bertram Windle assures his readers that "no person who knows anything about him can doubt the sincerity of his attachment to the Catholic Church," and all Catholic writers use much the same scandalous language.
Patrice Debré. Louis Pasteur. JHU Press. 2000: 176. ISBN 9780801865299. Does this mean that Pasteur was bound to a religious ideal? His attitude was that of a believer, not of a sectarian. One of his most brilliant disciples, Elie Metchnikoff, was to attest that he spoke of religion only in general terms. In fact, Pasteur evaded the question by claiming quite simply that religion has no more place in science than science has in religion. ...A biologist more than a chemist, a spiritual more than a religious man, Pasteur was held back only by the lack of more powerful technical means and therefore had to limit himself to identifying germs and explaining their generation.
Brendon Barnett. Louis Pasteur: A Religious Man?. Pasteur Brewing. 2011-05-31 [2012-08-11]. （原始內容存檔於2012-11-14）. However, unlike many others, Pasteur asserted the preeminence of hypotheses over religious or metaphysical prejudices and always seemed willing to abandon theories that were outdated or useless in practicality. Pasteur often saw religion as a hinderance to scientific progress. In 1874, presiding over the award ceremony at the Collège of Arbois, he clearly stated his position: "I know that the word free thinker is written somewhere within our walls as a challenge and an affront. Do you know what most of the free thinkers want? Some want the freedom not to think at all and to be fettered by ignorance; others want the freedom to think badly; and others still, the freedom to be dominated by what is suggested to them by instinct and to despise all authority and all tradition. Freedom of thought in the Cartesian sense, freedom to work hard, freedom to pursue research, the right to arrive at such truth as is accessible to evidence and to conform one's conduct to these exigencies--oh! let us vow a cult to this freedom; for this is what has created modern society in its highest and most fruitful aspects." Pasteur had great respect for the unknown and the infinite, but did not allow himself to become a victim of superstition and fanatical religious explanations.
Brendon Barnett. Louis Pasteur: A Religious Man?. Pasteur Brewing. 2011-05-31 [2012-08-11]. （原始內容存檔於2012-11-14）. Louis Pasteur did not deny religion, but was compelled to say that, "religion has no more place in science than science has in religion." The role of religion in his mind was clear: "In each one of us there are two men, the scientist and the man of faith or of doubt. These two spheres are separate, and woe to those who want to make them encroach upon one another in the present state of our knowledge!"
William C. Summers. Pasteur’s ‘Private Science’. New York Review of Books. February 6 [2013-10-17]. （原始內容存檔於2015-10-29）. 請檢查|date=中的日期值 (幫助) 引文格式1維護：日期與年 (link)
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