WASHINGTON, June 18 (Reuters) - U.S. Senate Democrats

demanded on Wednesday Health Secretary Robert F. Kennedy Jr.

make public the reviews on which his department said it based

its decision to cancel a contract for developing a bird flu

vaccine.

President Donald Trump's administration last month canceled

a $590-million contract awarded to Moderna ( MRNA ) in January

by outgoing President Joe Biden's administration for the

late-stage development of its bird flu vaccine for humans, as

well as the right to purchase shots.

"This is a grievous mistake that threatens to leave the

country unprepared for what experts fear might be the next

pandemic - and there appears to be no rationale for this

decision other than your ill-informed and dangerous war on

vaccines," Senators Elizabeth Warren and Tammy Duckworth wrote

in a letter seen by Reuters.

The cancellation endangers American lives and will likely

contribute to a 20% rise in the price of eggs this year, they

wrote to Kennedy, who has a long history of questioning the

safety of vaccines contrary to scientific evidence.

A spokesperson for the Department of Health and Human

Services at the time said the contract was canceled after a

comprehensive internal review determined the project did not

meet the scientific standards or safety expectations required

for continued federal investment.

Warren and Duckworth demanded Kennedy make the review

public, alongside a similar review the department cited when it

cut funding of a $258-million program researching an HIV

vaccine. They also asked for a detailed description of how the

department decided to end the contracts, and a staff briefing.

"You have failed to justify either of these moves to cripple

vaccine research," Warren and Duckworth wrote. "Furthermore,

these decisions appear to be part of your larger, unfounded

vendetta against mRNA technology."

Kennedy named eight members last week to serve on a panel of

vaccine advisers to the U.S. Centers for Disease Control and

Prevention, including some who have advocated against vaccines,

days after abruptly firing all 17 members who had been serving

on the independent committee of experts.

Several of his appointees specifically oppose the mRNA

vaccine technology used in some of the newest immunizations such

as the COVID-19 vaccine, including by Moderna ( MRNA ).