Over the past several weeks, I have received dozens of messages from readers concerned about whether they will be able to access vaccines in the near future. They are right to be worried, especially after Health and Human Services Secretary Robert F. Kennedy Jr. replaced vaccine experts advising the Centers for Disease Control and Prevention with his own appointees, some of whom are anti-vaccine activists.

Many readers want to know what will happen with flu and coronavirus vaccines this fall. “As a former health care professional, I am appalled by the [termination] of HHS employees,” wrote Cindy from Arizona. “I am wondering if we will even have seasonally updated vaccines for influenza and the coronavirus this year and in the future.”

Patti from Maryland had a similar concern: “Though I appreciate your columns on where to go for reliable vaccine guidance, the issue I am most concerned about is whether there will be vaccines at all. Specifically, I am 70 … and every year, my husband and I get flu shots as well as coronavirus vaccines. I read that there will not be a new flu shot this fall, so even if we have info on what is best to get, what are we supposed to do to get it? I also worry for my granddaughter, who will be 4 this fall. She has not had her second measles vaccine yet. This is really stressing me out.”

Martha from Wisconsin, who is over 65 and has asthma, is also “profoundly concerned” about the availability of vaccines. “I do not trust what is occurring [in the United States] and find myself wondering if there will be an emerging market for vaccine tourism,” she said. “I’ll be in Canada in late August and am wondering if it’s worth attempting to get the flu vaccine during that trip. It would be earlier than I typically get it, but if I have the choice of early or not at all, I’ll do it.”

And Paul from Oregon, 82, is wondering if he should try to get the coronavirus vaccine now while it is still available. “My doctor has been saying for months that I could get another shot, but am I better-off getting the old one or waiting until the fall? Or should I get it now in case RFK Jr. decides against coronavirus shots?”

Let me begin by addressing flu shot availability. Last week, the newly-appointed CDC advisers voted to stop recommending influenza vaccines that contain a preservative called thimerosal. This followed a presentation from a noted vaccine critic that ignored the extensive body of research disproving any health risks from vaccines containing the compound.

The good news is that only about 4 percent of flu vaccines distributed in the United States contain thimerosal. If the CDC accepts the advisers’ guidance, the immediate impact on flu vaccine availability will probably be minimal.

Officials have also indicated that this year’s flu vaccines will be available as before. In March, the Food and Drug Administration issued recommendations to manufacturers about virus strains to target for the 2025-2026 flu vaccine. It explicitly stated that “the FDA does not anticipate any impact on timing or availability of vaccines for the American public.”

So I think it’s very likely there will be a suitable flu vaccine available this fall, as in previous years. I don’t think Martha needs to seek a flu shot in August during her trip to Canada, since she should be able to receive it in the United States. (I recommend October as the ideal time to ensure maximal immunity throughout flu season.)

My concerns about the thimerosal vote are with its longer-term implications. This is a preservative that helps keep multidose vaccines free from bacterial contamination. In the event of an influenza pandemic, banning its use could hamper mass vaccination campaigns. The vote also raises serious questions about the objectivity and scientific rigor of Kennedy’s appointees. If they cherry-picked data to make decisions on thimerosal, how will they vote on other vaccine questions in the future?

Though I believe we will continue to have seasonal flu vaccines, I am far less confident about the future of coronavirus vaccines, which Kennedy has long targeted. On the one hand, the FDA signaled that it intends to preserve access to the shot for seniors and people with underlying medical conditions. But federal health officials have already made it harder for some such vulnerable groups, most notably pregnant women, to get the vaccine. And at least one Kennedy-appointed adviser has spread deeply troubling misinformation about the vaccines, including suggesting that they cause a form of AIDS.

So I just don’t know what will happen with the coronavirus shots. It’s probable that an updated vaccine will be made available to older individuals in the fall. Still, I would advise people such as Paul who are eligible to receive the 2024-2025 vaccine to get it now while they can. That vaccine should still offer good protection against severe disease caused by currently circulating variants. If a new vaccine becomes available in the fall, older individuals will still be eligible for it. The CDC has said people can receive the updated vaccine if it’s been at least two months since their last shots.

As for Patti’s question regarding childhood vaccines, the measles, mumps and rubella vaccine remains available and recommended for children. Her granddaughter should have no issues finishing her MMR series in the fall (the second dose is recommended between ages 4 and 6). Whether this will remain the case going forward is far from clear. The new chair of the CDC vaccine advisory committee has said it will reexamine the childhood immunization schedule and the administration of certain vaccines, including the hepatitis B vaccine and the combination measles, mumps, rubella and chicken pox vaccines.

It’s worth stepping back to consider how deeply troubling this moment is. People who want vaccines to protect themselves and their families should not have to wonder whether this option will remain available. For those who are uncertain about vaccines, the mere suggestion of revisiting vaccines long known to be safe and effective lends credibility to fears that have no basis in science. That this skepticism is now being propagated at the highest levels of government is not just irresponsible; it is an open invitation to preventable outbreaks and unnecessary suffering.

Leana S. Wen, a Washington Post contributing columnist who writes the newsletter The Checkup with Dr. Wen, is an emergency physician, clinical associate professor at George Washington University and author of “Lifelines: A Doctor’s Journey in the Fight for Public Health.”