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Pandemic Data Outlook

The State of State-Level Breakthrough Case Reporting

COVID-19 breakthrough case data is essential for tracking the virus and monitoring vaccine efficacy. Only 35 states report this data and only a portion of them report the data in a useful format. We need clear, consistent reporting of this data across all 50 states.

Beth Blauer, Associate Vice Provost, JHU
September 7, 2021

Dr. William Moss and I recently explained the need to collect data on breakthrough cases and report that data in a standardized manner across states, given the lack of federal guidance. When discussing breakthrough cases it is essential to remember that breakthrough cases are expected and normal, but it is still important to record and share data on them. The vaccines work against all current variants of the SARS-CoV-2 virus, including the delta variant.1 We know this in part due to breakthrough case data reported by the CDC: compared to unvaccinated individuals infected with SARS-CoV-2, vaccinated individuals were much less likely to develop severe disease and much less likely to die from the virus.2

The CDC only reports breakthrough cases that rise to the level of hospitalization,3 putting the burden of complete data reporting on state health departments. This creates a gap in knowledge regarding infection and transmission patterns in communities with mixed vaccination status. Additionally, the formalities required for states to report to the CDC can cause the aggregate CDC dataset to lag behind actual trends.4 Every state needs to describe the vaccination status of those who test positive, are hospitalized with COVID-19, and who die of COVID-19.

State Breakthrough Data Report Card

As of Aug. 30, only 35 states and Washington, D.C. publicly report breakthrough cases in any form (shown in the map below). Although some states that do not offer regular public reporting of COVID-19 data will share the information upon direct request,5 public reporting is the gold standard for data availability. This map highlights the inconsistent methods states use to report breakthrough cases. States publish the data with varying levels of detail through COVID-19 dashboards, state health department websites, PDF reports, press releases, and, in certain cases social media.6


Which states do not report any breakthrough case data? The list is long: Colorado, Florida, Hawaii, Iowa, Kansas, Kentucky, Missouri, Nevada, New Hampshire, New York, Pennsylvania, South Dakota, Texas, and Wyoming. Choosing not to report breakthrough cases with detailed metadata makes it nearly impossible to track COVID-19 surges, variants, and vaccine effectiveness. Residents of these states could be using breakthrough case data to make daily decisions that impact the health of their families. States have a responsibility to provide this critical data to their residents.

Model Students

At a minimum, states must regularly report breakthrough cases. However, some reporting methods are better than others, and there are some states that could serve as models. The best data reporting method is through established COVID-19 dashboards with downloadable functionality. All states (apart from Nebraska)7 still maintain COVID-19 data dashboards, and breakthrough data should be incorporated into them. Examples of excellent dashboards with breakthrough case data are: Indiana, North Dakota, and Wisconsin (pictured below).


Not only has Wisconsin reported detailed breakthrough data, it has also provided insightful visualizations that highlight the efficacy of vaccination and the dangers of choosing to remain unvaccinated. Other states still report data through their dashboards or health department websites without the same functionality and ability to download plain text files containing the raw data. That option is less ideal, but still preferable to release of data in PDFs and press releases, because these data are not always machine-readable. Data can still be scraped if PDFs are regularly formatted and uploaded to the same destination, but without consistent formatting the data must be manually recorded. As usual, consistency is key.

States need to report breakthrough case data in a manner that provides context and access to raw data. The states reporting breakthroughs in any format are still outperforming their peers that do not report the data.

Individualized Data Plan for the United States

This incomplete reporting and inconsistent formatting make it difficult to anticipate when the Coronavirus Resource Center will be able to report on breakthrough case data. States are significantly hampering efforts to define the national landscape of COVID-19 breakthrough cases by not reporting the data, or reporting it infrequently in atypical formats. The delta variant is already ravaging the United States, and other variants may arise in the future.8 We need detailed, real-time information on breakthrough cases to monitor for vaccine efficacy and to defend against new surges.

States are responsible for protecting their residents, and providing data on breakthrough cases during a global pandemic should be a key component of that effort. While the federal government has not yet mandated public reporting of breakthrough case data, the states should take it upon themselves to provide the best, most detailed data on breakthrough cases that they can. Some states have led the way and shown that they can provide this data in a clear, informative, up-to-date manner. It is time for the rest to follow their lead.

1. J. Lopez Bernal, N. Andrews, C. Gower, E. Gallagher, R. Simmons, S. Thelwall, J. Stowe, E. Tessier, N. Groves, G. Dabrera, R. Myers, C.N.J. Campbell, G. Amirthalingam, M. Edmunds, M. Zambon, K.E. Brown, S. Hopkins, M. Chand, M. Ramsay, Effectiveness of Covid-19 Vaccines against the B.1.617.2 (Delta) Variant, New England Journal of Medicine 385(7) (2021) 585-594.
2. COVID-19 Vaccines Work, 16 August 2021. (Accessed 30 August 2021).
3. COVID-19 Vaccine Breakthrough Case Investigation and Reporting. (Accessed 17 August 2021).
4. J. Musgrave, Florida accuses CDC of inflating COVID numbers in apparent CDC mistake, 10 August 2021. (Accessed 11 August 2021).
5. C. Mui, 15 states are keeping COVID-19 breakthrough cases under wraps, 06 August 2021. (Accessed 16 August 2021).
6. A.P. Health, Breakthrough Cases in Alabama, 23 August 2021.
7. P. Ricketts, Gov. Ricketts Ends Coronavirus State Of Emergency, Nebraska Department of Health and Human Services, 28 June 2021.
8. A. Winning, South Africa detects new coronavirus variant, still studying its mutations, 30 August 2021. (Accessed 30 August 2021).

Breakthrough case figure taken from Wisconsin Department of Health Services

Beth Blauer, Associate Vice Provost, JHU

Beth Blauer is the Associate Vice Provost for Public Sector Innovation and Executive Director of the Centers for Civic Impact at Johns Hopkins. Blauer and her team transform raw COVID-19 data into clear and compelling visualizations that help policymakers and the public understand the pandemic and make evidence-based decisions about health and safety.