Anthony Fauci, the nation’s top infectious disease specialist, told a House panel Friday that he is “cautiously optimistic” that a COVID-19 vaccine would be ready by the end of this year and said health agencies are not compromising safety standards.

“I know to some people this seems like it is so fast that there might be compromising of safety and scientific integrity,” Fauci said at a hearing by the Select Subcommittee on the Coronavirus Crisis. “I can tell you that is absolutely not the case.”

Fauci said a vaccine may not immediately be available to everyone once it’s available, but that “over a period of time in 2021” the public would be able to access a vaccine, assuming one is authorized.

Both Oversight and Reform Chairwoman Carolyn B. Maloney of New York and Republican Rep. Jackie Walorski of Indiana pressed Fauci on the likelihood that a vaccine would become available soon and whether Americans should be concerned it would not face rigorous testing.

“I’m so disappointed that we’ve seen some on the other side of the aisle speculate aloud that the administration might rush an unsafe vaccine to the market before the election to help President Trump politically,” Walorski said.