Infectious Disease Expert’s Testimony on Vaccine Hesitancy Admitted
Posted on September 19, 2025 by Expert Witness Profiler
This case arises out of Plaintiff Cheyanne Dixson’s 2022 termination as a police officer with the Issaquah Police Department after Defendant, the City of Issaquah, determined it could not accommodate Plaintiff’s religious exemption to vaccination against SARS-CoV-2, an employment requirement implemented by Defendant during the COVID-19 pandemic. Dixon was a patrol officer in the City’s Police Department.
Defendant produced the expert report of John Lynch, M.D., a board-certified physician in infectious disease. Lynch’s proffered testimony includes background information on the COVID-19 pandemic and the development of the first COVID-19 vaccines. Plaintiff filed a motion to exclude all testimony by Lynch.
Infectious Disease Expert Witness
John B. Lynch is a board-certified physician in infectious disease. He currently works as an Associate Medical Director of Harborview Medical Center and a Professor of Medicine at the University of Washington (UW) and actively practices medicine as an infectious disease clinician.
His work at Harborview included serving as the medical director for the occupational health program, and he also served on the Board of Directors of the Infectious Diseases Society of America from 2019 to 2022.
Lynch earned his Doctor of Medicine (“MD”) from the UW School of Medicine in 2002 and his Master’s in Public Health (“MPH”) in epidemiology and global health from the UW School of Public Health in 2011.
Discussion by the Court
Plaintiff asserted that Lynch is not qualified to opine as an expert except on the “efficacy of [CV-19] vaccines,” that his opinions are irrelevant and unreliable, and that his testimony and report will confuse the issues and should be excluded.
A. Rule 702 Challenge
1. Lynch’s Qualifications
The Court held that Lynch is abundantly qualified by both experience and training to render the opinions he offered. Plaintiff has not produced evidence to negate these qualifications.
2. Relevance of Opinions
Defendant offered Lynch’s testimony in support of its “undue hardship” defense to Plaintiff’s claim, under the Washington Law Against Discrimination, that Defendant discriminated against her by failing to accommodate her sincerely held religious belief.
To prevail on its undue hardship defense, Defendant will need to establish that the accommodation sought by Plaintiff—here, remaining unvaccinated and fulfilling her usual job duties but submitting to twice-weekly COVID-19 tests, masking during work hours while in the presence of others, and eating her meals in her car, outdoors, or off site—would result in “substantial increased costs in relation to the conduct of [Defendant’s] particular business.”
Plaintiff repeatedly asserted that information about vaccines and safety risks is irrelevant but does not explain how the health-and safety-related cost Plaintiff’s unvaccinated status imposed on Defendant can be evaluated without this information.
The one argument that Plaintiff presented as to why these topics are irrelevant—”because the Plaintiff was exempt from the vaccine requirement . . . .” —would appear to foreclose any consideration of health risks or other intrinsic “costs” of waiving an employment requirement for an objecting employee. But it is hard to see how an undue burden defense could ever be adjudicated without information about the purpose and value of the employment requirement from which a Plaintiff is exempt or seeking exemption.
3. Reliability of Opinions
Lynch explained in his declaration that his opinions were formed based on knowledge gained in “decades of working in clinical infectious diseases, infectious disease research, public health, and epidemiology,” the medical studies and public health data he cited in his declaration and report, his review of over a dozen documents from this case, and a visit to the Issaquah Police Department.
Though Defendant provided extensive case law on medical expert testimony in its response, Plaintiff offered no reply. Accordingly, the Court found that Lynch’s opinions have “a reliable basis in the knowledge and experience of the relevant discipline.”
Further, where the particular facts of the case are relevant to Lynch’s opinions, he considered them with specificity. For example, he considers Plaintiff’s work duties, the settings in which she worked, and the people with whom she interacted in her role as a police officer.
4. Plaintiff’s Other Arguments
Repeatedly, in support of her arguments on both relevance and reliability, Plaintiff argued for exclusion based not on opinions Lynch has offered but opinions he has not offered, mostly related to Plaintiff’s preferred framing of “the key issue” in this case: how could masking and testing be safe and effective from October to February and then unsafe or ineffective starting February 16, 2022.
Plaintiff also faults Lynch for not being able to precisely quantify “the residual risk of acquisition and transmission” by an unvaccinated person with Plaintiff’s accommodations and not opining on the actual incidence of breakthrough infections among Defendant’s employees or Defendant’s reliance on recommendations by the Centers for Disease Control and Prevention.
Assuming for the sake of argument that these “missing” opinions are relevant and otherwise admissible, the Court held that their absence is a subject for cross-examination, not a basis for exclusion of Lynch’s testimony under Rule 702.
B. Rule 403 Challenge
5. Testimony on Vaccine Development and Approval
Plaintiff objected to Lynch testifying about the development and Federal Drug Administration (“FDA”) approval of vaccines on the grounds that such testimony is both irrelevant and prejudicial, contending that “the introduction of these facts is more likely to prejudice the trier of fact by implying that [Plaintiff] contests vaccines and FDA approval and/or importance or efficacy. This is simply not true and the inclusion is prejudicial.”
As to the relevance of these issues, the Court agreed with Defendant that “[t]his data provides relevant background information about options available to the City and others to control the spread of COVID-19 in the workplace in late 2021 and early 2022.”
As to any potential undue prejudice, Plaintiff explained neither how facts about vaccine history and development imply anything at all about Plaintiff’s personal opinions, nor how such an implication could be prejudicial when the very basis of this case arises out of Plaintiff’s religious objection to a workplace vaccination requirement.
6. Opinions on Vaccine Hesitancy and Misinformation
Plaintiff also objected to a section of Lynch’s report entitled “Vaccine Hesitancy and Misinformation,” on the grounds that it “is likely to be more prejudicial than beneficial to the inquiry.” Besides this assertion, however, Plaintiff offered no argument on this topic.
According to the Court, this alone is a sufficient basis to reject Plaintiff’s unreasoned request for exclusion.
The Court noted, moreover, that most of the opinions Lynch offered in the challenged section are directly responsive either to specific statements in Plaintiff’s complaint or to arguments advanced by Plaintiff during this litigation.
7. Purported Opinion Regarding Temporary Accommodation
Finally, Plaintiff argued that Lynch’s purported opinion that Defendant should not have accommodated Plaintiff even temporarily “will likely confuse the trier of fact, not assist them.” The Court need not consider the likelihood of confusion because Plaintiff presented no evidence that Lynch has ever expressed this opinion.
The other testimony cited by Plaintiff arose from a question about why Defendant would have accommodated her; Lynch responded that he was neither a human resources person nor involved in the conversations. Lynch tried to discern the rationale by reading the documents with which he was presented and responded that accommodating Plaintiff was a policy decision by human resources. Nowhere in the referenced material did he opine that Defendant should not have accommodated Plaintiff.
These exchanges, viewed along with their mischaracterization here by Plaintiff’s counsel (who also deposed Lynch), create the impression that counsel, not having solicited the deposition testimony she wanted from Lynch, decided to distort his testimony beyond recognition. The Court will give counsel the benefit of the doubt and assume that this was an honest mistake rather than a willful misrepresentation.
Held
The Court denied the Plaintiff’s motion to exclude the opinions of Defendant’s expert John Lynch.
Key Takeaway:
In ignoring the applicable standards, Plaintiff presented no clear argument that Lynch’s experience did not support his conclusions (and the Court finds that it does); that his reasoning is circular, speculative, or otherwise flawed (and the Court finds that it is not); or that his reasoning is not adequately explained (and the Court finds that is is).
Lynch explained in his declaration that his opinions were formed based on knowledge gained in “decades of working in clinical infectious diseases, infectious disease research, public health, and epidemiology,” the medical studies and public health data he cites in his declaration and report, his review of over a dozen documents from this case, and a visit to the Issaquah Police Department. This is clearly consistent with the types of sources typically relied on by medical professionals.
Case Details:
| Case Caption: | Rosa V. City Of Issaquah Et Al |
| Docket Number: | 2:24cv1673 |
| Court Name: | United States District Court for the Western District of Washington |
| Order Date: | September 15, 2025 |
