Top 5 Takeaways

  1. Expansion of Laboratory Testing: In December 2016, the Minnesota Department of Health expanded laboratory testing for varicella, showing that among 208 patients with a clinical diagnosis, 45% tested positive for varicella-zoster virus (VZV), highlighting the importance of laboratory confirmation in diagnosing varicella.
  2. Vaccine Impact on Diagnosis: The detection of VZV was significantly lower in vaccinated individuals (22%) compared to those unvaccinated (66%), demonstrating the diagnostic challenges posed by the modified clinical appearance of varicella in vaccinated persons.
  3. Public Health Implications: Clinical diagnosis of varicella can be unreliable, particularly among vaccinated patients. Laboratory confirmation is crucial for accurate clinical and public health management, understanding epidemiology, and evaluating vaccine effectiveness.
  4. Testing Methodology and Accessibility: The use of polymerase chain reaction (PCR) testing for VZV, alongside offering specimen collection kits directly to individuals and through partnerships with schools and childcare facilities, has improved testing accessibility and reliability in Minnesota.
  5. Educational and Outreach Efforts: Outreach initiatives, including newsletters, health advisories, webinars, and direct follow-ups with healthcare providers, have been instrumental in promoting varicella testing and ensuring proper management of suspected cases.

Original Article Author and Citation

Corresponding Author

Alison Ruprecht,

Suggested Citation

Ruprecht A, Marin M, Strain AK, Harry K, Kenyon C. Notes from the Field: Expanded Laboratory Testing for Varicella — Minnesota, 2016–2023. MMWR Morb Mortal Wkly Rep 2024;73:245–246. DOI:


The initiative by the Minnesota Department of Health (MDH) to expand laboratory testing for varicella in December 2016 has led to significant findings that impact clinical diagnosis and public health management of varicella, particularly in the context of vaccinated individuals. This expansion aimed at improving the accuracy of varicella diagnoses through PCR testing and promoting better clinical and public health outcomes.


The expanded testing initiative involved various methods to increase testing accuracy and accessibility, including outreach to healthcare providers, direct follow-up on testing practices, providing specimen collection kits, and performing PCR testing for VZV and other viruses at the MDH Public Health Laboratory.


The findings from this expanded testing initiative highlight the challenges in clinically diagnosing varicella, especially among vaccinated individuals. The efforts to increase laboratory testing for varicella have doubled the proportion of laboratory-confirmed cases, underscoring the importance of PCR testing in both vaccinated and unvaccinated populations for accurate diagnosis and management.


The initiative to expand laboratory testing for varicella in Minnesota underscores the importance of laboratory confirmation in the accurate diagnosis and management of varicella, especially in the context of the vaccination program. Increased testing, coupled with educational and outreach efforts, has contributed to more reliable diagnoses and appropriate management of varicella cases.

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