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Changes in Rates of Measles Transmission and Force of Infection in Gweru City, Zimbabwe: A Retrospective Study

Received: 4 February 2016     Accepted: 16 February 2016     Published: 2 March 2016
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Abstract

Introduction A study compared rates of measles transmission and force of infection in pre-vaccination era (1967), and at measles vaccine coverage rates of 50-80% (1978-84) and > 90% (1989). Using measles surveillance data cumulative proportions of measles cases by age were determined for the years 1967, 1978-89 (pooled) and 1989. From the cumulative curves estimates of the age dependent rate of infection with measles (force of infection) was determined for the years 1967, 1978-84 and 1989. Results In 1967 and 1978-84 some 75% of all measles cases occurred by age group 36-47 months while in 1989 this occurred by age group 72-83 months thus measles transmission was most rapid in 1967 and least rapid in 1989. Variation of force of infection between years 1967, 1978-84 and 1967 showed that force of infection was not significantly different between the years for age groups 24-35, 36-47 and 48-59 months. Meanwhile, the force of infection varied between the years in the rest of the age groups, with a significant reduction in force of infection over the years for age groups < 11, and 12-23 months; and significant increases in force of infection were observed in the age groups 60-71, 72-83, 84-95, 96-107 and 108-119 months. Conclusion Measles transmission rates in the community were highest in pre-vaccination era and least at vaccination coverage rates of > 90% most likely due to effect of herd immunity. From pre-vaccination era (1967) to vaccine coverage rates of > 90% (1989) there was a shift in force of infection from young age groups < 23 months to older age groups of 60-119 months most likely due to accumulation of susceptibles in these older age groups. Shift in force of infection to older age groups would have been responsible for the shift in age at infection to these older age groups.

Published in European Journal of Preventive Medicine (Volume 4, Issue 2)
DOI 10.11648/j.ejpm.20160402.11
Page(s) 28-31
Creative Commons

This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.

Copyright

Copyright © The Author(s), 2016. Published by Science Publishing Group

Keywords

Measles, Transmission Rates, Force of Infection, Gweru City, Zimbabwe

References
[1] Moss WJ. Measles still has a devastating impact in unvaccinated populations. PLoS Med 2007; 4(1): e24.
[2] Andre FE, Booy R, Bock HL, Clemens J, Datta SK, John TJ, Lee W et al. Vaccination greatly reduces disease, disability, death and inequality worldwide. Bull WHO 2008; 86: 81-160.
[3] Goodson JL, Masresha BG, Wannemuehler K, Uzicanin A, Cochi S. Changing epidemiology of measles in Africa. J Infect Dis 2011; 204 Suppl 1: S205-14.
[4] Grenfell BT, Anderson RM. The estimation of age related rates of infection from case notifications and serological data. J Hyg Camb 1985; 95: 419-436 (methodology).
[5] Morley D. Severe Measles. In: Paediatric Priorities in the Developing World. Butterworts, 1979: 207-230.
[6] Willingham E, Helft L. What is Herd Immunity? www.pbs.org/wgbh/nova/body/herd-immunity.html [accessed 06 December 2015]
[7] Garnnet GP. Role of herd immunity in determining the effect of vaccines against sexually transmitted disease J Infect Dis, 2005; 191 (Suppl 1): S97-106.
[8] John TJ, Samuel R. Herd immunity and herd effect: new insights and definitions. E J Epidemiol, 2000; 16: 601-606.
[9] Anderson RM, May RM. Vaccination and herd immunity to infectious diseases. Nature, 1985; 318: 323-329.
[10] Anderson RM, May RM. Infectious diseases of humans: dynamics and control. Oxford: Oxford University Press; 1991.
[11] Fine P, Eames K, Heymann DL. “Herd Immunity”: A rough guide. Clin Infect Dis, 2011; 52: 911-916.
[12] Fine PEM. Herd Immunity: History, Theory, Practice. Epidemiologic Reviews, 1993; 15: 265-302.
[13] Nokes DJ, Anderson RM. Measles, mumps and rubella vaccine: what coverage to block transmission? Lancet 1988; 2: 1374.
[14] Centers for Disease Control and Prevention. Measles In: Epidemiology and prevention of vaccine-preventable diseases, 13th Edition April 1995: 209-229.
[15] Marufu T, Murugasampillay S, Siziya S, Manyame B, Silape-Marufu Z, Xaba E et al. Is protection afforded vaccinees the same in children of all age groups? Cent Afr J Med 1995; 41: 144-7.
[16] Global Programme for Vaccines and Immunization. Immunization Policy. Expanded Programme on Immunization, WHO/EPI/GEN/92.3. WHO. Geneva: WHO; 1995.
[17] Coetzee N, Hussey GD, Visser G, Barron P, Keen A. The 1992 measles epidemic in Cape Town-a changing epidemiological pattern S Afr Med J 1994; 84(3): 145-9.
[18] Khuri-Bulos NA. Measles in Jordan: a prototype of the problems with measles in developing countries. Pediatr Infect Dis J 1995; 14(1): 22-6.
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  • APA Style

    Tawanda Marufu, Willard Tinago, Seter Siziya. (2016). Changes in Rates of Measles Transmission and Force of Infection in Gweru City, Zimbabwe: A Retrospective Study. European Journal of Preventive Medicine, 4(2), 28-31. https://doi.org/10.11648/j.ejpm.20160402.11

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    ACS Style

    Tawanda Marufu; Willard Tinago; Seter Siziya. Changes in Rates of Measles Transmission and Force of Infection in Gweru City, Zimbabwe: A Retrospective Study. Eur. J. Prev. Med. 2016, 4(2), 28-31. doi: 10.11648/j.ejpm.20160402.11

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    AMA Style

    Tawanda Marufu, Willard Tinago, Seter Siziya. Changes in Rates of Measles Transmission and Force of Infection in Gweru City, Zimbabwe: A Retrospective Study. Eur J Prev Med. 2016;4(2):28-31. doi: 10.11648/j.ejpm.20160402.11

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  • @article{10.11648/j.ejpm.20160402.11,
      author = {Tawanda Marufu and Willard Tinago and Seter Siziya},
      title = {Changes in Rates of Measles Transmission and Force of Infection in Gweru City, Zimbabwe: A Retrospective Study},
      journal = {European Journal of Preventive Medicine},
      volume = {4},
      number = {2},
      pages = {28-31},
      doi = {10.11648/j.ejpm.20160402.11},
      url = {https://doi.org/10.11648/j.ejpm.20160402.11},
      eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.ejpm.20160402.11},
      abstract = {Introduction A study compared rates of measles transmission and force of infection in pre-vaccination era (1967), and at measles vaccine coverage rates of 50-80% (1978-84) and > 90% (1989). Using measles surveillance data cumulative proportions of measles cases by age were determined for the years 1967, 1978-89 (pooled) and 1989. From the cumulative curves estimates of the age dependent rate of infection with measles (force of infection) was determined for the years 1967, 1978-84 and 1989. Results In 1967 and 1978-84 some 75% of all measles cases occurred by age group 36-47 months while in 1989 this occurred by age group 72-83 months thus measles transmission was most rapid in 1967 and least rapid in 1989. Variation of force of infection between years 1967, 1978-84 and 1967 showed that force of infection was not significantly different between the years for age groups 24-35, 36-47 and 48-59 months. Meanwhile, the force of infection varied between the years in the rest of the age groups, with a significant reduction in force of infection over the years for age groups Conclusion Measles transmission rates in the community were highest in pre-vaccination era and least at vaccination coverage rates of > 90% most likely due to effect of herd immunity. From pre-vaccination era (1967) to vaccine coverage rates of > 90% (1989) there was a shift in force of infection from young age groups < 23 months to older age groups of 60-119 months most likely due to accumulation of susceptibles in these older age groups. Shift in force of infection to older age groups would have been responsible for the shift in age at infection to these older age groups.},
     year = {2016}
    }
    

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  • TY  - JOUR
    T1  - Changes in Rates of Measles Transmission and Force of Infection in Gweru City, Zimbabwe: A Retrospective Study
    AU  - Tawanda Marufu
    AU  - Willard Tinago
    AU  - Seter Siziya
    Y1  - 2016/03/02
    PY  - 2016
    N1  - https://doi.org/10.11648/j.ejpm.20160402.11
    DO  - 10.11648/j.ejpm.20160402.11
    T2  - European Journal of Preventive Medicine
    JF  - European Journal of Preventive Medicine
    JO  - European Journal of Preventive Medicine
    SP  - 28
    EP  - 31
    PB  - Science Publishing Group
    SN  - 2330-8230
    UR  - https://doi.org/10.11648/j.ejpm.20160402.11
    AB  - Introduction A study compared rates of measles transmission and force of infection in pre-vaccination era (1967), and at measles vaccine coverage rates of 50-80% (1978-84) and > 90% (1989). Using measles surveillance data cumulative proportions of measles cases by age were determined for the years 1967, 1978-89 (pooled) and 1989. From the cumulative curves estimates of the age dependent rate of infection with measles (force of infection) was determined for the years 1967, 1978-84 and 1989. Results In 1967 and 1978-84 some 75% of all measles cases occurred by age group 36-47 months while in 1989 this occurred by age group 72-83 months thus measles transmission was most rapid in 1967 and least rapid in 1989. Variation of force of infection between years 1967, 1978-84 and 1967 showed that force of infection was not significantly different between the years for age groups 24-35, 36-47 and 48-59 months. Meanwhile, the force of infection varied between the years in the rest of the age groups, with a significant reduction in force of infection over the years for age groups Conclusion Measles transmission rates in the community were highest in pre-vaccination era and least at vaccination coverage rates of > 90% most likely due to effect of herd immunity. From pre-vaccination era (1967) to vaccine coverage rates of > 90% (1989) there was a shift in force of infection from young age groups < 23 months to older age groups of 60-119 months most likely due to accumulation of susceptibles in these older age groups. Shift in force of infection to older age groups would have been responsible for the shift in age at infection to these older age groups.
    VL  - 4
    IS  - 2
    ER  - 

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Author Information
  • Department of Community Medicine, University of Zimbabwe College of Health Sciences, Harare, Zimbabwe

  • Department of Community Medicine, University of Zimbabwe College of Health Sciences, Harare, Zimbabwe

  • Department of Clinical Sciences, Copperbelt University School of Medicine, Ndola, Zambia

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