Maxi-Vac and Maxi-Vac Alternative 2.0, Smallpox Vaccination Clinic Planning Tool

What’s New?

Maxi-Vac (2.0) and Maxi-Vac Alternative (2.0) are updated versions of Maxi-Vac and Maxi-Vac Alternative. The updates, made in October 2021, focus on presenting these tools in a spreadsheet-based format. Both the original tools were produced in a Visual Basic format which presented software compatibility issues. The data underlying the calculations and results presented in Maxi-Vac (2.0) and Maxi-Vac Alternative (2.0) remain unchanged.

Overview of Maxi-Vac

The World Health Organization formally declared the eradication of smallpox in May 1980. Following this major public health accomplishment, smallpox vaccinations concluded throughout the world. Although the last recorded natural case of smallpox occurred in 1977, the intentional release of the smallpox virus may be a potentially devastating bioterrorism threat.

To help states and local communities prepare to respond to a potential smallpox attack, the U.S.  Centers for Disease Control and Prevention has released generic guidelines on how to set up a smallpox vaccination clinic. However, individual states and communities have differing numbers of qualified personnel that would be available in such an event.

Maxi-Vac (2.0) and Maxi-Vac Alternative (2.0) help a public health official answer the following question: “How can I allocate the limited number of personnel available so that the maximum number of people are vaccinated in a 24-hour period?”

Maxi-Vac uses a mathematical simulation model, assumed time spent in each station, and your input (e.g., the number of personnel available for each shift in a clinic) to optimally allocate personnel and maximize the number of people vaccinated in a clinic during a 24 hour-period. Technical details and other assumptions used in Maxi-Vac (2.0) and Maxi-Vac Alternative (2.0) are provided in the manual.

Getting Started with the Simulation Model

We recommend downloading and saving the spreadsheet tool to your computer so that you can open the spreadsheet from your computer. This will allow the spreadsheet to open in Excel instead of your web browser.

Download the Maxi-Vac Tool and User Manual

If you encounter any issues with the tool or need assistance with accessibility, please contact

Considerations for Using the Model

The numbers generated by the tool should not be considered as predictions; rather, they are estimates of what could happen given the user input and assumptions.

You are encouraged to run the model several times. Once you are comfortable using the tool, you may wish to consider a plan wherein you systematically alter the values of input variables. You may alter one variable at a time (univariate sensitivity analysis) or alter the values of two or more variables simultaneously (multivariate sensitivity analysis).

Differences between Maxi-Vac and Maxi-Vac Alternative

Between the two tools, there are differences in the number of personnel that a user can select (i.e., how many physicians, nurses, and other non-medical staff can be selected) in the stations of the mass vaccination clinic (i.e., the size of the orientation room, the need for orientation and/or witnesses), and the percentage of families that need more detailed pre-vaccination medical screening. Processing times at the stations vary between the two versions. See the manual for more details on the specific differences.

Which version should I use?

Each public health unit is likely to face unique circumstances when standing up vaccination clinics. You are strongly encouraged to examine the differences between Maxi-Vac (2.0) and Maxi-Vac Alternative (2.0) before deciding which version to use. Maxi-Vac (2.0) may be best suited for larger vaccination clinics as it allows for more staff and larger orientation rooms, while Maxi-Vac Alternative (2.0) may be better suited to see how potentially optional stations affect the flow of people vaccinated in a 24-hour period. In addition, Maxi-Vac Alternative (2.0) assumes a much shorter processing time in the orientation, medical screening, and physician evaluation stations. It also possible to use both versions of the tool and compare results between versions to get a range of people vaccinated, instead of a precise number. Results from both models should not be viewed as definitive, but rather as a guide to the first steps in planning such clinics.


Please keep in mind that the numbers generated should not be considered predictions of what will occur while running a mass immunization clinic. Rather, they are estimates of what could happen. The findings and conclusions of this manual and software are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention.

Additional Reference

Washington ML, Mason J, and Meltzer MI (2005). Maxi-Vac: A tool to assist in planning mass smallpox vaccination clinics. Journal of Public Health Management and Practice, 11(6):542-9.