Zach Most, MD, MSc

My views expressed are my own
Assistant Professor of Pediatric Infectious Disease at UTSW
Associate Director of Infection Prevention at Children's Health Dallas

[Zach Most, MD, MSc @ZMostMD]

There have already been more measles cases in the US in 2026 than in all but 4 years since 1997 (two of which are 2024 and 2025). We are just two weeks in. The best way to protect yourself and your family is to stay up to date with MMR/MMRV vaccine

[Zach Most, MD, MSc @ZMostMD]

The poorly thought out changes to the US vaccine schedule will ultimately lead to dead American children. I fail to see how ignoring US public health experts in favor of foreign ones (who were unaware they were setting US vaccine policy) is putting "America first"

[Zach Most, MD, MSc @ZMostMD]

Flu season is here. In Dallas, we are seeing a mix a influenza A and B. Although, nationally it appears it is mostly just influenza A (H3N2). What do Dallas, Salt Lake City, New Orleans, and Detroit have in common? https://t.co/o3evkVPW2L

[Zach Most, MD, MSc @ZMostMD]

Google has a little trouble figuring out who the author of the IDSA COVID-19 guidelines is...

[Zach Most, MD, MSc @ZMostMD]

When did CDC start referring to mpox as "monkeypox" again? https://t.co/BeSmt2c7st

[Zach Most, MD, MSc @ZMostMD]

https://t.co/b3if5e8xmA

[DrDemetre @dr_demetre]

My resignation letter from CDC.

Dear Dr. Houry,

I am writing to formally resign from my position as Director of the National Center for Immunization and Respiratory Diseases at the Centers for Disease Control and Prevention (CDC), effective August 28, 2025, close of business.   I am happy to stay on for two weeks to provide transition, if requested.

This decision has not come easily, as I deeply value the work that the CDC does in safeguarding public health and am proud of my contributions to that critical mission. However, after much contemplation and reflection on recent developments and perspectives brought to light by Secretary Robert F. Kennedy Jr., I find that the views he and his staff have shared challenge my ability to continue in my current role at the agency and in the service of the health of the American people. Enough is enough.

While I hold immense respect for the institution and my colleagues, I believe that it is imperative to align my professional responsibilities to my system of ethics and my understanding of the science of infectious disease, immunology, and my promise to serve the American people.  This step is necessary to ensure that I can contribute effectively in a capacity that allows me to remain true to my principles.

I am unable to serve in an environment that treats CDC as a tool to generate policies and materials that do not reflect scientific reality and are designed to hurt rather than to improve the public’s health.  The recent change in the adult and children’s immunization schedule threaten the lives of the youngest Americans and pregnant people.   The data analyses that supported this decision have never been shared with CDC despite my respectful requests to HHS and other leadership.  This lack of meaningful engagement was further compounded by a “frequently asked questions” document written to support the Secretary’s directive that was circulated by HHS without input from CDC subject matter experts and that cited studies that did not support the conclusions that were attributed to these authors.  Having worked in local and national public health for years, I have never experienced such radical non-transparency, nor have I seen such unskilled manipulation of data to achieve a political end rather than the good of the American people.

It is untenable to serve in an organization that is not afforded the opportunity to discuss decisions of scientific and public health importance released under the moniker of CDC.  The lack of communication by HHS and other CDC political leadership that culminates in social media posts announcing major policy changes without prior notice demonstrate a disregard of normal communication channels and common sense.  Having to retrofit analyses and policy actions to match inadequately thought-out announcements in poorly scripted videos or page long X posts should not be how organizations responsible for the health of people should function.  Some examples include the announcement of the change in the COVID-19 recommendations for children and pregnant people, the firing of scientists from ACIP by X post and an op-ed rather than direct communication with these valuable experts, the announcement of new ACIP members by X before onboarding and vetting have completed, and the release of term of reference for an ACIP workgroup that ignored all feedback from career staff at CDC.

The recent term of reference for the COVID vaccine work group created by this ACIP puts people of dubious intent and more dubious scientific rigor in charge of recommending vaccine policy to a director hamstrung and sidelined by an authoritarian leader.   Their desire to please a political base will result in death and disability of vulnerable children and adults.  Their base should be the people they serve not a political voting bloc.

I have always been first to challenge scientific and public health dogma in my career and was excited by the opportunity to do so again.  I was optimistic that there would be an opportunity to brief the Secretary about key topics such as measles, avian influenza, and the highly coordinated approach to the respiratory virus season.  Such briefings would allow exchange of ideas and a shared path to support the vision of “Making America Healthy Again.”  We are seven months into the new administration, and no CDC subject matter expert from my Center has ever briefed the Secretary.  I am not sure who the Secretary is listening to, but it is quite certainly not to us.  Unvetted and conflicted outside organizations seem to be the sources HHS use over the gold standard science of CDC and other reputable sources.  At a hearing, Secretary Kennedy said that Americans should not take medical advice from him.  To the contrary, an appropriately briefed and inquisitive Secretary should be a source of health information for the people he serves. As it stands now, I must agree with him, that he should not be considered a source of accurate information.

The intentional eroding of trust in low-risk vaccines favoring natural infection and unproven remedies will bring us to a pre-vaccine era where only the strong will survive and many if not all will suffer.  I believe in nutrition and exercise.  I believe in making our food supply healthier, and I also believe in using vaccines to prevent death and disability.  Eugenics plays prominently in the rhetoric being generated and is derivative of a legacy that good medicine and science should continue to shun.

The recent shooting at CDC is not why I am resigning.  My grandfather, who I am named after, stood up to fascist forces in Greece and lost his life doing so.  I am resigning to make him and his legacy proud.   I am resigning because of the cowardice of a leader that cannot admit that HIS and his minions’ words over decades created an environment where violence like this can occur.  I reject his and his colleagues’ thoughts and prayers, and advise they direct those to people that they have not actively harmed.

For decades, I have been a trusted voice for the LGBTQ community when it comes to critical health topics.  I must also cite the recklessness of the administration in their efforts to erase transgender populations, cease critical domestic and international HIV programming, and terminate key research to support equity as part of my decision.

Public health is not merely about the health of the individual, but it is about the health of the community, the nation, the world. The nation’s health security is at risk and is in the hands of people focusing on ideological self-interest.

I want to express my heartfelt gratitude for the opportunities for growth, learning, and collaboration that I have been afforded during my time at the CDC. It has been a privilege to work alongside such dedicated professionals who are committed to improving the health and well-being of communities across the nation even when under attack from within both physically and psychologically.

Thank you once again for the support and guidance I have received from you and previous CDC leadership throughout my tenure. I wish the CDC continued success in its vital mission and that HHS reverse its dangerous course to dismantle public health as a practice and as an institution.  If they continue the current path, they risk our personal well-being and the security of the United States.

Sincerely,

Demetre C. Daskalakis MD MPH (he/his/him)

[Zach Most, MD, MSc @ZMostMD]

2024 National Immunization Survey - Teen show that only 63% (!) of teens in the USA are up to date with HPV vaccine. HPV vaccine is safe and prevents cancer. AAP recommends HPV vaccine for all 9 to 11 year olds.

[Jake Scott, MD @jakescottMD]

BOTTOM LINE:

When “evidence” relies on phantom papers, misquotes, 48‑year‑old Soviet data, and math that doesn’t add up - while ignoring results from millions of kids - you’re not doing science; you’re spreading misinformation.

The IOM, CDC, FDA, WHO, and researchers from four countries have reviewed thimerosal repeatedly. Their conclusion is consistent:

No link to autism
No credible harm at vaccine‑level exposure

Vaccine policy must be driven by solid evidence, not paranoia or phantom studies.

Full breakdown with citations:
https://t.co/osfILMLEtd

[Zach Most, MD, MSc @ZMostMD]

Discouraging the development of vaccines against Influenza H5N1 cannot possibly "Make America Healthy"

[Zach Most, MD, MSc @ZMostMD]

HICPAC provided invaluable expert patient safety recommendations. Eliminating HICPAC is absurd and will lead to preventable harm to patients and healthcare workers all over the country.

https://t.co/tONm2vyaJH

[IDSA @IDSAInfo]

We cannot do the complex and serious work of protecting Americans from infectious diseases amid this chaos and confusion.

Our statement on April 1 HHS Job Cuts: https://t.co/8ErZPdKmPO

[Zach Most, MD, MSc @ZMostMD]

"The profound loss of the critical expertise at the Department of Health and Human Services... will make our country significantly less safe from both chronic and infectious diseases." - IDSA President Tina Tan, MD https://t.co/3zsmzv9cDC

[Zach Most, MD, MSc @ZMostMD]

Unsure how to interpret hepatitis B serologies? How about measles serologies in a child who was recently vaccinated? I just learned about Serology Education which is a fantastic quick resource for these kinds of questions https://t.co/hUFjT3z1a6

[Zach Most, MD, MSc @ZMostMD]

https://t.co/sfBbPGqHcX

[Zach Most, MD, MSc @ZMostMD]

There is a rapidly growing measles outbreak in west Texas. Texas DSHS today reporting 48 cases, all of whom were unvaccinated (or had unknown status). The best way to keep you and your children safe from measles is to ensure you are update on MMR vaccine

https://t.co/vve7EZ5rUL

[Zach Most, MD, MSc @ZMostMD]

@NIH This is staggeringly short sighted. Thousands will lose their jobs, including many who work in the private sector. To offset the loss, healthcare costs are going to rise. Inflation and Unemployment

[IDSA @IDSAInfo]

The removal of #HIV- and #LGBTQ-related resources from the websites of the @CDCgov and other health agencies is deeply concerning.

Access to this information is crucial for ID and HIV health care professionals.

Our full statement: https://t.co/xcqdZ6515p

[Zach Most, MD, MSc @ZMostMD]

CDC has also removed it's information for the public on how to prevent HIV infection. https://t.co/CyySH5r31m It seems the intent of the federal government is to make us all as unhealthy as possible.

[Zach Most, MD, MSc @ZMostMD]

CDC has apparently taken down its STI treatment guidelines. https://t.co/tjGwq5vCiQ This move is incredibly short sighted and dangerous for all Americans.