Table of Contents  
Year : 2015  |  Volume : 6  |  Issue : 2  |  Page : 116-117  

VACCRaksha Calc: A computer program for the calculation of vaccine potency

1 Department of Veterinary Pharmacology and Toxicology, Veterinary College, Hyderabad, India
2 Department of Pharmacology, Andhra Medical College, Vizag, Andhra Pradesh, India

Date of Web Publication20-Apr-2015

Correspondence Address:
SaiMahesh Reddy Avula
Department of Veterinary Pharmacology and Toxicology, Veterinary College, Hyderabad
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0976-500X.155495

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How to cite this article:
Avula SR, Avula VR. VACCRaksha Calc: A computer program for the calculation of vaccine potency. J Pharmacol Pharmacother 2015;6:116-7

How to cite this URL:
Avula SR, Avula VR. VACCRaksha Calc: A computer program for the calculation of vaccine potency. J Pharmacol Pharmacother [serial online] 2015 [cited 2021 Dec 7];6:116-7. Available from:

Assessment of vaccine potency is often carried out by veterinarians in animal house in biological units. The more reliable method used for this assessment is Spearman and Karber. The calculations involved in the assessment are complex, confusing, time consuming and not easily reproducible. Spreadsheet is a computer application in which data are arranged in rows and columns of a grid and can be manipulated and used in calculations. In today's era of smart phones, tablet PCs and netbooks, where a spreadsheet program in the form of Microsoft Excel is readily accessible by most veterinarians, it should be possible to adapt the various laborious steps involved in the said method to a spreadsheet program by writing simple logical codes in the spreadsheets to do the calculations in a simple, clear, faster, reproducible, accurate and user-friendly manner. This article describes a spreadsheet program (VACCRaksha Calc) to calculate the vaccine potency based on the steps involved in Spearman and Karber [Figure 1].
Figure 1: Calculation sheet used in the laboratory (conventional method)

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Vaccine potency calculation

The spreadsheet program is based on the various steps for evaluation of vaccine potency by Spearman [1] and Karber [2] method.

According to them log 10 of end point dilution of vaccine is given by the formula

- [Xo - D/2 + D (∑ R/N)]


Xo = log 10 of the reciprocal of the lower dilution at which all animals are protected

D = log 10 of the dilution factor

R = number of mice died due to specific symptoms

N = number of animals used at each individual dilution (after discounting accidental or nonspecific deaths)

The spreadsheet program used is Microsoft Excel version 2013. [3]

Coding and logical data used in this program are as follows;

For D11 cell (mice alive)

=D9-D10 (also applied for E, F and G11 cells)

For D13 cell (sum of r/n) it's been,

=IF (E12 < 1, D12 + E12 + F12 + G12)

For E13 cell,

=IF (E12 = 1, E12 + F12 + G12)

For D14 cell (multiplication with log of dilution factor)


For D15 cell (deletion of 0.35)

=IF (E12 < 1, D14-0.35)

For E15 cell (addition of 0.35)

=IF (E12 = 1, E14 + 0.35)

For Antilog calculation i.e. E15 cell,

=IF (E12 < 1, 10^D15)

For D17 cell (relative potency)

=IF (E12 < 1, D16/18)

One representative study is presented to help and understand the usefulness of the program. The findings of the experiment along with the calculation are presented as a screenshot of the program [Figure 2].
Figure 2: Snapshot taken from the actual spreadsheet of potency calculation

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The difficulty which usually concerns veterinarians in biological units is the virus titer or end point dilution assessment. They often encounter the following problems:

  • The calculations involved in the assessment are time consuming
  • The calculations appear confusing when reviewed at a later date
  • It is often difficult to explain in a report or communication how the final figure was arrived at.

The program described here can easily solve the above problems. It can be used to store, process, analyze and graphically represent data. A formula entered in a cell in the spreadsheet defines how the content of that cell is to be calculated from the contents of any other cell(s) each time the content of the other cell(s) is updated.

The program was thoroughly tested for the entire range of possible values. As the spreadsheet makes the whole process of assessment faster and user friendly, the program will be useful to veterinary professionals who are working in biological units.

   References Top

Spearman C. The method of "Right and Wrong Cases" ("Constant Stimuli") without Gauss's formulae. Br J Psychol 1908;2:227-42.  Back to cited text no. 1
Karber G. 50% end-point calculation. Arch Exp Pathol Pharmak 1931;162:480-3.  Back to cited text no. 2
Available from: [Last accessed on 2014 Dec 26].  Back to cited text no. 3


  [Figure 1], [Figure 2]


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