Not sure what Fauci is really trying to say. Vaccines are given to a person so that antibodies against the disease can develop over time. These newly formed antibodies prevent the disease from taking hold when a person has been exposed, preventing that person from becoming sick with the disease.
From John Hopkins:
International Vaccine Access Center
How do vaccines work?
Vaccines stimulate the human body’s own protective immune responses so that, if a person is infected with a pathogen, the immune system can quickly prevent the infection from spreading within the body and causing disease. In this way, vaccines mimic natural infection but without actually causing the person to become sick.
For SARS-CoV-2, antibodies that bind to and block the spike protein on the virus’s surface are thought to be most important for protection from disease because the spike protein is what attaches to human cells, allowing the virus to enter our cells. Blocking this entrance prevents infection.
Not all people who are infected with SARS-CoV-2 develop disease (Covid-19 is the disease caused by the virus SARS-CoV-2). These people have asymptomatic infection but can still transmit the virus to others.
In general, most vaccines do not completely prevent infection but do prevent the infection from spreading within the body and from causing disease. Many vaccines can also prevent transmission, potentially leading to herd protection whereby unvaccinated people are protected from infection by the vaccinated people around them because they have less chance of exposure to the virus.
Bttt.