Bulletin of the World Health Organization

Paperless registration during survey enumerations and large oral cholera mass vaccination in Zanzibar, the United Republic of Tanzania

Mohammad Ali a, Jaqueline L Deen a, Ahmed Khatib b, Godwin Enwere c, Lorenz von Seidlein a, Rita Reyburn a, Said Mohammed Ali b, Na Yoon Chang a, Valérie Perroud c, Frédérique Marodon c, Abdul A Saleh b, R Hashim a, Anna Lena Lopez a, James Beard a, Benedikt N Ley a, Kamala Thriemer a, Mahesh K Puri a, Binod Sah a, Mohamed Saleh Jiddawi b & John D Clemens a

a. International Vaccine Institute, Kwanak PO Box-14, Seoul, 151-600, Republic of Korea.
b. Ministry of Health and Social Welfare, Zanzibar, Tanzania
c. World Health Organization, Geneva, Switzerland

Correspondence to Mohammad Ali (e-mail: mali@ivi.int).

(Submitted: 23 March 2009 – Revised version received: 07 October 2009 – Accepted: 22 October 2009.)

Bulletin of the World Health Organization 2010;88:556-559. doi: 10.2471/BLT.09.070334


Accurate, complete and timely data documentation is a major challenge in conducting field research. Traditionally, studies begin with information recorded on paper followed by double data entry to detect keypunching errors.1 This complicated and time-consuming approach is fraught with difficulties when dealing with large data sets, limited availability of qualified staff, expensive equipment and frequent power interruptions. A paper-based system may also delay the availability of clean data sets needed for subsequent research activities, including mass vaccination and disease surveillance with linkage to vaccination status.

Hand-held computers, also known as personal digital assistants (PDAs), are increasingly being applied in developing countries to computerize health information.24 PDAs have been used for health surveys,4,5 patient assessments and follow-ups,3,6 and they have been combined with other information technologies in demographic surveillance systems.2 In studies in developing countries in which paper questionnaires have been compared directly to PDAs, improved data precision, decreased collection time and fewer errors have been found.7 The advantages of PDAs are that fewer individuals are required, and that cleaned data sets are available immediately after field work.8

We programmed, designed and supervised the use of PDAs for a survey enumeration followed by a large mass vaccination campaign in Zanzibar. In this paper we report our experiences with direct entry of data into PDAs and provide recommendations for future use.

The project

Zanzibar, in the United Republic of Tanzania, consists of two main islands, Unguja and Pemba, where outbreaks of cholera have been reported since the 1970s. Our project (registration number NCT00709410), known as “Pre-emptive use of cholera vaccination in high-risk populations in Zanzibar” or CHOZAN, which is short for “cholera in Zanzibar”, consisted of mass cholera vaccination in high-risk populations of approximately 50 000 individuals for the purpose of assessing vaccine effectiveness and potential herd protection.

Hardware and software

We used 30 iPAQ 214 Enterprise Hand-held (Hewlett Packard, Palo Alto, United States of America) PDAs with a 4-inch (10.2-centimetre) touch screen display and a Microsoft Windows Mobile® 5.2 operating system (Microsoft Corporation, Redmond, USA). Each PDA had a 2200 milli Ampere hour (mAh) lithium ion rechargeable battery that provided at least 6 hours of usage, and a backup battery was provided for each operator. We developed data entry systems using Visual Basic.Net (Microsoft, Seattle, USA). To upload and manage the data on a desktop computer, we developed another system using Microsoft Visual FoxPro® 7.0.

Survey enumerations

The survey was conducted from 3 November 2008 to 31 December 2008. Survey instruments included questions on the following: household-level socioeconomic markers, basic demographic information, health utilization behaviour and recent travel. We provided training on the use of PDAs to 24 field workers with at least a secondary school education and no previous experience in direct data entry or hand-held computers. Sample screens of the PDA survey enumerations are available at: https://trdrdcsys.ivi.int/pda/pic1.asp. Data entry fields included option buttons, check boxes or spaces where data could be inserted. Drop-down menus, skipping of fields and fields requiring data were programmed into the system to prevent errors during navigation through the questionnaire. The data collected in the PDAs were uploaded into a central computer at the end of each work day. Further checks were performed in the central computer immediately after uploading the data.

Vaccination registration

After the survey enumeration was completed and the database was cleaned, household identification (ID) cards were printed and distributed in early January 2009. All healthy, non-pregnant residents of the study sites who were ≥ 2 years of age were invited to participate in the mass vaccination campaign. The first round of vaccination was conducted from 17 to 26 January 2009, and the second one was conducted from 7 to 16 February 2009. This ensured a minimum of 12 days between doses. There were nine vaccination outposts in each of the islands.

We downloaded into the PDA basic individual information from the population database. The vaccination registration system included two modules: one with and the other without an ID card. The flow of the vaccination registration system is shown in Fig. 1. If the individual brought the ID card, the PDA registrar used the “ID card” module (the sample screen of the vaccine registration is available at: https://trdrdcsys.ivi.int/pda/pic2.asp). It then provided basic information on the individual that was verified before registering the person’s vaccination status. If the individual came without the ID card, the ID-search module (a sample screen of the PDA is available at: https://trdrdcsys.ivi.int/pda/pic3.asp) was used to search for the person. It took approximately 10 seconds to generate the list of potential candidates. A touch on the target individual brought up a PDA screen for vaccination registration.

Fig. 1. Flow diagram of vaccine registration for mass oral cholera vaccination campaign, Zanzibar, United Republic of Tanzania, 2009
Fig. 1. Flow diagram of vaccine registration for mass oral cholera vaccination campaign, Zanzibar, United Republic of Tanzania, 2009
ID, identification; PDA, personal digital assistants.a Shehias are small administrative ward subdivisions in Zanzibar.

At the end of each vaccination day, the PDAs were collected from all vaccination posts. The data from the PDAs were then merged into a single database on the designated computer, and a report was produced. The merged database was downloaded into each of the PDAs so the vaccination status of a given individual could be pulled up from any one of the PDAs as a protection against duplicating a vaccination.

Quality control and data integration

The PDA system included automatic check functions and a response confirmation feature in the data entry programs. At the end of each day, rigorous checking was performed; an error list was created and sent for resolution the following day. During mass vaccination, vaccination data were linked directly to the population data in the PDA. This allowed for immediate and correct linking of the data at the point of contact.

Data security and audit trail

The survey enumeration included identifiers and was considered a source document for the population base. The database was downloaded and backed up daily. For data security, the PDAs were password-protected and locked in secured locations. Only investigators conducting the study had direct access to the database, the backed up data and the PDAs. We kept the data from each day’s activities stored in the desktop computer. A trail of all changes made to the data, the date of each change and the identity of the individual who introduced the change were all recorded.

PDA acceptability and performance

After training and home practice, field workers were able to handle the PDAs efficiently in 2 to 3 days. During survey enumerations, 31 213 residents of Unguja and 16 723 residents of Pemba were enumerated. Each field worker was able to complete approximately 20 household interviews in one day. During vaccination, 29 507 two-dose vaccine recipients were registered. No major problems were associated with the use of PDAs except for difficulty in reading the screen under direct sunlight. Data could be efficiently entered with a stylus. Questionnaire skip patterns were easily navigated, and missing data were eliminated. The entry of erroneous or inconsistent data was prevented through in-built checks in the PDA. The logistics of collecting the PDAs daily to download data and charge batteries were less complex than those involved in using paper forms.

Cost comparison

Paperless and paper-based systems require a similar number of field staff and supervisors for data collection and they entail similar training costs. The paperless system in our study involved the cost of 30 PDAs (12 000 United States dollars, US$), 1 central computer and printer (US$ 2500), software (US$ 500) and PDA system development (US$ 20 000). This added up to a total of US$ 35 000. In contrast, a paper-based system would have required US$ 17 000 to US$ 22 000, since we would have needed to employ a much larger staff for a longer period (about six data entry clerks and one supervisor for 4 months, at an overall cost of approximately US$ 7000 to US$ 10 000). Another US$ 10 000 to US$ 12 000 would have been needed for computers, printers, photocopiers, power backup facilities, paper, filing cabinets and the rental of a larger office space. Finally, development costs would have been the same for a paper-based system as for the PDA system.

Evaluation and lessons learnt

To our knowledge, we have been the first to use PDAs for direct data entry during a survey enumeration followed by mass vaccination. PDA data collection was reliable and provided rapid data summaries, and field workers were able to use PDAs easily (Box 1). The data were promptly and accurately linked as well as easily accessible for integrated analysis and report generation. We did not experience any hardware problems and we lost no PDAs or data.

Box 1. Summary of main lessons learnt

  • Personal digital assistants (PDAs) allow one to digitize information at the initial point of contact between interviewers and respondents.
  • Immediate response by the PDA system in case of error while digitizing data in front of the respondents ensures the data quality and reliability.
  • A PDA system helps produce quick data summaries and allows one to carry out subsequent research activities in a timely fashion.

Implementing paperless data management required a large initial capital cost for the purchase of hardware. However, this was offset by savings on expenses that would have been incurred if paper questionnaires had been used. We are still generating savings because the programmed PDAs continue to be used for subsequent study activities. The major challenge involved in paperless data entry was the need for expert programming capability to design, develop and implement an efficient system. Visual Basic.Net, which we used to customize our PDA software required some development time but provided a user-friendly system. Another challenge was to train inexperienced field workers to use a hand-held device. Field workers took the PDAs home to become familiar with the technology, and any problems they encountered were reported and resolved in the next training session.

The PDAs made it possible to digitize information at the initial point of contact between the respondents and interviewers and provided data immediately after survey enumerations. This shortened the transition time to vaccination and subsequently to disease surveillance. The PDAs are now being used to update the population database and, at treatment centres, to conduct surveillance of diarrhoeal diseases. Our experience suggests that people with little education and no experience in the use of a computer are easily able to use a PDA.


We would like to acknowledge M-P Kieny and MT Aguado for their overall supervision of the CHOZAN project, and C-L Chaignat for her role in the initiation of the project.

Members of the CHOZAN project (in alphabetical order within institute): SM Ali, MS Jiddawi and AM Khatib (Ministry of Health and Social Welfare, Zanzibar, United Republic of Tanzania); JD Clemens, JL Deen, L von Seidlein (International Vaccine Institute, Seoul, Republic of Korea); C Schaetti, M Weiss (Swiss Tropical and Public Health institute, Basel, Switzerland); MT Aguado, R Bos, R Hutubessy, G Enwere, M-P Kieny, (World Health Organization, Geneva, Switzerland); D Sack (Johns Hopkins Bloomberg School of Public Health, Baltimore, USA) on behalf of the CHOZAN technical advisory committee.


The CHOZAN Project is coordinated by the WHO Initiative for Vaccine Research, Geneva, Switzerland, and has received financial support from the Bill & Melinda Gates Foundation. Additional funding has been provided by the Swedish International Development Cooperation Agency.

Competing interests:

None declared.