Drugmakers racing to develop a safe and effective coronavirus vaccine pledged on Tuesday to ensure their larger clinical trials would include diverse sets of volunteers.

In prepared remarks for a U.S. congressional hearing, several companies vowed to include broad representation as they prepare to launch studies with thousands of volunteers in the coming months.

“Ensuring diversity in these trials, including in terms of race, ethnicity, gender, age, and other factors, is a priority in our efforts,” Menelas Pangalos, AstraZeneca Plc’s executive vice president of biopharmaceutical research & development, said in prepared remarks ahead of the hearing held by the House subcommittee on oversight and investigations.

A group of physicians and scientists last week urged the U.S. government to include Black, Latino and indigenous Americans in the design and implementation of COVID-19 vaccine trials in hopes of building trust among these at-risk populations.

Representatives from Johnson & Johnson, Moderna Inc, Pfizer Inc, and Merck & Co Inc were also set to testify later on Tuesday in the hearing, which is focused on efforts to develop a safe, effective and accessible COVID-19 vaccine.

More than 150 vaccines are in development globally with an aim to help end the global pandemic that has claimed more than 600,000 lives. But whether any will succeed remains far from clear.

Early data from trials of three potential COVID-19 vaccines released on Monday, including a closely watched candidate from AstraZeneca and Oxford University, increased confidence that a vaccine can train the immune system to recognize and fight the novel coronavirus without serious side effects.