Christian T. K.-H. Stadtlander, Microbiologist & Epidemiologist, St. Paul, Minnesota, U.S.A.
20 August 2012
I read with interest the article by Hope et al. [1] who conducted a cross-sectional study of pertussis vaccination of child care workers in Australia. Through interviewing the directors of child care centers, the authors found that 63% of centers participating in the study (i.e., 202/319) kept records of staff vaccinations, while 58% of centers with records (117/202) reported that less than half of their staff members were vaccinated. Furthermore, the study revealed that 74% of centers (125/170), which regularly updated records, did this only when a staff member notified them about vaccinations. Hope et al. [1] concluded that better monitoring and higher levels of vaccination would help reducing the risk of pertussis cases and outbreaks in Australian child care centers. This study is important and deserves further discussion since there has been a reemergence of pertussis cases in many regions around the world, making it a global problem [2].
Pertussis is a highly contagious and acute respiratory tract infection caused primarily by Bordetella pertussis, a Gram-negative aerobic bacterium which produces several toxins, including the pertussis toxin [3,4]. The disease is characterized by severe, prolonged cough (whooping cough), can easily be transmitted through direct contact, and can affect individuals at any age, but is particularly dangerous for babies and young children [2-4]. The World Health Organization reported an estimated 50 million cases of whooping cough and 300,000 deaths occurring every year, with case-fatality rates in developing countries as high as 4% in infants [5].
Whooping cough is a vaccine-preventable disease. Immunization for all adults and adolescents is considered the single most effective strategy to prevent the spread of pertussis among babies and children too young to be fully vaccinated [2-4,6]. There are several guidelines on the use of vaccination in adults against pertussis; however, these guidelines vary among countries [1-3,6,7]. Hope et al. [1] pointed out that child care centers in Australia are required to keep records of the vaccination status of children, and that those children who are not vaccinated be excluded from the centers. There appears, however, to be no similar policy in place for child care workers. In light of these facts and the findings of the relatively low pertussis vaccination coverage not only in child care workers [1] but also in health care workers [3,4,7,8], it is clear that vaccination coverage, policy, and practice must be improved in order to prevent pertussis outbreaks and protect infants.
Since the availability of pertussis vaccines, the number of pertussis cases has significantly dropped [3,9,10]. However, it appears that immunity after pertussis vaccination decreases over time, leading to a growing population of susceptible adolescents and adults [4,7]. Outbreaks of whooping cough occur typically in cycles every 3 to 4 years [3]. However, in recent years, there is an increase in the incidence of pertussis cases, which is believed to be caused by several factors, including improved surveillance and detection, a shift of pertussis cases to older age groups, and changes in routine immunization rates in some countries [2,3,7,8]. It is noteworthy that most recently there was a significant outbreak of pertussis in Washington State (United States) that began in mid-2011 [11]. By June 16, 2012, the reported number of cases in Washington State had reached 2,520 (37.5 cases per 100,000 residents), which has been calculated to be a 1,300% increase compared with the same period in 2011. The report mentioned that this is the highest number of cases reported in any year since 1942 [11].
The study by Hope et al. [1] showed that 67% (194/288) of the child care center directors interviewed had not asked or did not know why staff members did not receive a pertussis vaccination, and 16% (45/288) were not aware that staff members needed to be vaccinated. These findings point to issues of knowledge about vaccination as well as deficiencies in communication among child care center personnel. I agree with the authors that providing directors with useful information and follow-up of vaccination status of staff members, as well as improvements in accreditation or licensing processes are crucial elements for a successful prevention program. However, I believe directors should also discuss important aspects of the disease itself, in particular the fact that diagnosis of whooping cough is sometimes difficult when symptoms are still nonspecific. The unfortunate result is that the disease can be misdiagnosed as a cold, leading to unrecognized and unreported cases. Staff members may not be aware that they actually have pertussis and carry the risk of transmitting the disease to others, including vulnerable infants.
The final point I would like to discuss relates to the study design. Hope et al. [1] mentioned several potential limitations of their study. For example, they discussed that the tested centers may not be representative for all child care centers in the state and that center directors ¿ not child care workers ¿ provided the responses to the questionnaires. Also, the authors pointed to potential issues with the questionnaire itself. I believe that other factors, such as information about the age distribution of child care center personnel (directors and child care workers) and possible personnel changes (turnarounds) before and during the study phase can have impacted the results. More specifically, there could have been variation in the knowledge of personnel about center-related issues, the willingness to provide specific answers, and the accuracy and completeness of responses to questions during the relatively short (about 10 minutes) telephone survey. Nevertheless, cross-sectional study designs are invaluable tools in research. They are useful to measure events at one point in time or over a short period of time (i.e., a snap-shot), are often based on a sample of the general population, and can be employed for public health planning [12,13].
References
1. Hope K, Butler M, Massey PD, Cashman P, Durrheim DN, Stephenson J, Worley A: Pertussis vaccination in child care workers: room for improvement in coverage, policy and practice. BMC Pediatrics 2012, 12:98.
2. Guiso N, Liese J, Plotkin S: The global pertussis initiative: meeting report from the fourth regional roundtable meeting, France, April 14-15, 2010. Hum Vaccin 2011, 7:481-488.
3. American Public Health Association: Control of Communicable Diseases Manual. 19th edition. Washington, D.C.: American Public Health Association; 2008.
4. Sandora TJ, Gidengil CA, Lee GM: Pertussis vaccination for health care workers. Clin Microbiol Rev 2008, 21:426-434.
5. World Health Organization: WHO-recommended surveillance standard of pertussis. http://www.who.int/immunization_monitoring/diseases/pertussis_surveillance/en/index.html. [Accessed 8/15/2012].
6. Centers for Disease Control and Prevention: Updated recommendations for use of tetanus toxoid, reduced diphtheria toxoid and acellular pertussis (Tdap) vaccine from the Advisory Committee on Immunization Practices. MMWR Morb Mortal Wkly Rep 2011, 60:13-15.
7. Hoffait M, Hanlon D, Benninghoff B, Calcoen S: Pertussis knowledge, attitude and practices among European health care professionals in charge of adult vaccination. Hum Vaccin 2011, 7:197-201.
8. Russi M: Pertussis vaccination of health care workers. J Occup Environ Med 2007, 49:700-702.
9. Cherry JD: Historical review of pertussis and the classical vaccine. J Infect Dis 1996, 174:S259-263.
10. Shapiro-Shapin CG: Pearl Kendrick, Grace Eldering, and the pertussis vaccine. Emerg Infect Dis 2010, 16:1273-1278.
11. Centers for Disease Control and Prevention: Pertussis epidemic ¿ Washington, 2012. MMWR Morb Mortal Wkly Rep 2012, 61:517-522.
12. Kelsey JL, Whittemore AS, Evans AS, Thompson WD: Methods in Observational Epidemiology. 2nd edition. New York, New York: Oxford University Press; 1996.
Importance of Pertussis Vaccination
20 August 2012
I read with interest the article by Hope et al. [1] who conducted a cross-sectional study of pertussis vaccination of child care workers in Australia. Through interviewing the directors of child care centers, the authors found that 63% of centers participating in the study (i.e., 202/319) kept records of staff vaccinations, while 58% of centers with records (117/202) reported that less than half of their staff members were vaccinated. Furthermore, the study revealed that 74% of centers (125/170), which regularly updated records, did this only when a staff member notified them about vaccinations. Hope et al. [1] concluded that better monitoring and higher levels of vaccination would help reducing the risk of pertussis cases and outbreaks in Australian child care centers. This study is important and deserves further discussion since there has been a reemergence of pertussis cases in many regions around the world, making it a global problem [2].
Pertussis is a highly contagious and acute respiratory tract infection caused primarily by Bordetella pertussis, a Gram-negative aerobic bacterium which produces several toxins, including the pertussis toxin [3,4]. The disease is characterized by severe, prolonged cough (whooping cough), can easily be transmitted through direct contact, and can affect individuals at any age, but is particularly dangerous for babies and young children [2-4]. The World Health Organization reported an estimated 50 million cases of whooping cough and 300,000 deaths occurring every year, with case-fatality rates in developing countries as high as 4% in infants [5].
Whooping cough is a vaccine-preventable disease. Immunization for all adults and adolescents is considered the single most effective strategy to prevent the spread of pertussis among babies and children too young to be fully vaccinated [2-4,6]. There are several guidelines on the use of vaccination in adults against pertussis; however, these guidelines vary among countries [1-3,6,7]. Hope et al. [1] pointed out that child care centers in Australia are required to keep records of the vaccination status of children, and that those children who are not vaccinated be excluded from the centers. There appears, however, to be no similar policy in place for child care workers. In light of these facts and the findings of the relatively low pertussis vaccination coverage not only in child care workers [1] but also in health care workers [3,4,7,8], it is clear that vaccination coverage, policy, and practice must be improved in order to prevent pertussis outbreaks and protect infants.
Since the availability of pertussis vaccines, the number of pertussis cases has significantly dropped [3,9,10]. However, it appears that immunity after pertussis vaccination decreases over time, leading to a growing population of susceptible adolescents and adults [4,7]. Outbreaks of whooping cough occur typically in cycles every 3 to 4 years [3]. However, in recent years, there is an increase in the incidence of pertussis cases, which is believed to be caused by several factors, including improved surveillance and detection, a shift of pertussis cases to older age groups, and changes in routine immunization rates in some countries [2,3,7,8]. It is noteworthy that most recently there was a significant outbreak of pertussis in Washington State (United States) that began in mid-2011 [11]. By June 16, 2012, the reported number of cases in Washington State had reached 2,520 (37.5 cases per 100,000 residents), which has been calculated to be a 1,300% increase compared with the same period in 2011. The report mentioned that this is the highest number of cases reported in any year since 1942 [11].
The study by Hope et al. [1] showed that 67% (194/288) of the child care center directors interviewed had not asked or did not know why staff members did not receive a pertussis vaccination, and 16% (45/288) were not aware that staff members needed to be vaccinated. These findings point to issues of knowledge about vaccination as well as deficiencies in communication among child care center personnel. I agree with the authors that providing directors with useful information and follow-up of vaccination status of staff members, as well as improvements in accreditation or licensing processes are crucial elements for a successful prevention program. However, I believe directors should also discuss important aspects of the disease itself, in particular the fact that diagnosis of whooping cough is sometimes difficult when symptoms are still nonspecific. The unfortunate result is that the disease can be misdiagnosed as a cold, leading to unrecognized and unreported cases. Staff members may not be aware that they actually have pertussis and carry the risk of transmitting the disease to others, including vulnerable infants.
The final point I would like to discuss relates to the study design. Hope et al. [1] mentioned several potential limitations of their study. For example, they discussed that the tested centers may not be representative for all child care centers in the state and that center directors ¿ not child care workers ¿ provided the responses to the questionnaires. Also, the authors pointed to potential issues with the questionnaire itself. I believe that other factors, such as information about the age distribution of child care center personnel (directors and child care workers) and possible personnel changes (turnarounds) before and during the study phase can have impacted the results. More specifically, there could have been variation in the knowledge of personnel about center-related issues, the willingness to provide specific answers, and the accuracy and completeness of responses to questions during the relatively short (about 10 minutes) telephone survey. Nevertheless, cross-sectional study designs are invaluable tools in research. They are useful to measure events at one point in time or over a short period of time (i.e., a snap-shot), are often based on a sample of the general population, and can be employed for public health planning [12,13].
References
1. Hope K, Butler M, Massey PD, Cashman P, Durrheim DN, Stephenson J, Worley A: Pertussis vaccination in child care workers: room for improvement in coverage, policy and practice. BMC Pediatrics 2012, 12:98.
2. Guiso N, Liese J, Plotkin S: The global pertussis initiative: meeting report from the fourth regional roundtable meeting, France, April 14-15, 2010. Hum Vaccin 2011, 7:481-488.
3. American Public Health Association: Control of Communicable Diseases Manual. 19th edition. Washington, D.C.: American Public Health Association; 2008.
4. Sandora TJ, Gidengil CA, Lee GM: Pertussis vaccination for health care workers. Clin Microbiol Rev 2008, 21:426-434.
5. World Health Organization: WHO-recommended surveillance standard of pertussis. http://www.who.int/immunization_monitoring/diseases/pertussis_surveillance/en/index.html. [Accessed 8/15/2012].
6. Centers for Disease Control and Prevention: Updated recommendations for use of tetanus toxoid, reduced diphtheria toxoid and acellular pertussis (Tdap) vaccine from the Advisory Committee on Immunization Practices. MMWR Morb Mortal Wkly Rep 2011, 60:13-15.
7. Hoffait M, Hanlon D, Benninghoff B, Calcoen S: Pertussis knowledge, attitude and practices among European health care professionals in charge of adult vaccination. Hum Vaccin 2011, 7:197-201.
8. Russi M: Pertussis vaccination of health care workers. J Occup Environ Med 2007, 49:700-702.
9. Cherry JD: Historical review of pertussis and the classical vaccine. J Infect Dis 1996, 174:S259-263.
10. Shapiro-Shapin CG: Pearl Kendrick, Grace Eldering, and the pertussis vaccine. Emerg Infect Dis 2010, 16:1273-1278.
11. Centers for Disease Control and Prevention: Pertussis epidemic ¿ Washington, 2012. MMWR Morb Mortal Wkly Rep 2012, 61:517-522.
12. Kelsey JL, Whittemore AS, Evans AS, Thompson WD: Methods in Observational Epidemiology. 2nd edition. New York, New York: Oxford University Press; 1996.
13. Marshall C, Rossman GB: Designing Qualitative Research. 4th edition. Thousand Oaks, California: Sage Publications; 2006.
Competing interests
The author declares no competing interests.