Students from the School of Medicine marched with an estimated 5 million people around the world in the Women’s March on Washington on Saturday, a day of support for human rights, including the right to affordable health care. Several groups of students traveled to the main march in Washington, D.C., while others participated in sister marches in New York and Boston.

The march, held the day after the inauguration of President Donald Trump, was a response to what participants see as threats from his new administration to civil liberties, human rights, reproductive freedom, and gender equality. The march, organizers said in their mission statement, “will send a bold message to our new government on their first day in office … that women’s rights are human rights. We stand together, recognizing that defending the most marginalized among us is defending all of us.”

According to organizers, the Washington march alone, one of about 670 around the world, drew more than 1 million marchers. Marches took place in all 50 states and in more than 15 countries.

For the medical students, a main concern was Trump’s pledge to repeal the Affordable Care Act (ACA), also known as Obamacare, which has insured upwards of 30 million people around the country.

“We think that health care is a human right, not a privilege,” said Andi Shahu, a fifth-year medical student who was with a group of classmates in Washington. “Everyone should have affordable access to health care. Everyone should have access to reproductive health care and mental health care. Everyone should be treated equally, regardless of their identity.”

Like other students in his group, Shahu said he found it encouraging to be among hundreds of thousands of people who share his concerns. “It was amazing to be there with what seemed like a million people in solidarity, who want the country to be the best it can be,” he said.

“It was inspiring and exciting to be among so many likeminded people and see the incredible turnout,” said Karrin Weisenthal, a fifth-year student who marched with Shahu, adding that there was one very important message from speakers who included Gloria Steinem, Senator Kamala Harris, actress America Ferrera, and others. “The work starts the day after the march. It is not just about showing up today, it is about showing up in your own community. The way we move forward from here is we get involved.”

For Weisenthal, affordable health care was a major issue, but she had other concerns about the new president. “The language that has been used to talk about women has been very upsetting to me,” she said.

Their group of about eight students gathered at about 9:30 Saturday morning in front of the National Air and Space Museum on the mall. The crowd grew, Shahu said, to the point where it became impossible to move. Moving just three feet could take five minutes, he said. Lines for portable toilets stretched for blocks.

Because they arrived before the official start time, Weisenthal said that they didn’t realize at first how much the crowd had grown. One of the students, Melody Hu, climbed a tree for a look and reported that the crowd stretched as far as the eye could see. When the march ended and it came time to leave, all the side streets remained thronged with people, Shahu and Weisenthal said.

Despite the crowds, the students said that marchers were patient, polite, and respectful. “It was peaceful,” Shahu said.

Valerie Luks, who stayed with Weisenthal in an apartment filled with marchers, with air mattresses and sleeping bags strewn about, was impressed by the diversity of the crowd, not just in gender and ethnicity, but in age as well. “It was amazing to see so many different generations at the march—from children in strollers to women in wheelchairs,” Luks said.

Erik Levinsohn, in Boston for a year of research at Brigham & Women’s Hospital, joined a group of Harvard medical students at a march on the Boston Common. “It was incredible to see Boston Common packed with people,” he said. “As future physicians we see the potential dismantling of health care as an issue we can’t stay silent for.”

“There was a lot of really positive energy,” said Matthew Meizlish, in his fifth year of the M.D./Ph.D. program, who attended the march in New York. “A lot of people are going to be really vulnerable under this administration. … This was a moment of solidarity and coming together and affirmation of the values and principles of the kind of world we want to move toward.”

Meizlish said that, despite his concerns on a range of issues, as a medical student and future doctor, there is one on which he can have the most impact. “To me, the potential repeal of the ACA is an immediate threat, it’s one that will directly affect my patients, and it’s the place where I am best positioned to inject my voice and help resist a regressive agenda,” he said.