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Feasibility of a Cocoon Strategy for the Prevention of Pertussis in Italy

A Survey of Prevention Department Healthcare Providers

Prato, Rosa MD*; Martinelli, Domenico MD, PhD*; Marchetti, Federico BSc; Fortunato, Francesca MD*; Tafuri, Silvio MD; Germinario, Cinzia A. MD

Author Information
The Pediatric Infectious Disease Journal: December 2012 - Volume 31 - Issue 12 - p 1304-1307
doi: 10.1097/INF.0b013e31826b7110

Abstract

According to the Global Pertussis Initiative, administering a booster dose of Tdap to close contacts of a newborn to protect the baby from pertussis is defined as “cocoon strategy.”1 In 2008, the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices emphasized the recommendation of a booster dose of Tdap among women of childbearing age who might become pregnant.2 Several countries have advised the cocoon strategy but, in 2010, the World Health Organization (WHO) concluded that there was inadequate evidence to recommend it, based on the weakness of data on the impact of cocoon to vaccinate household contacts, the significant programmatic difficulties, and the costs of vaccination campaign issues to be further investigated.3 In favor of the cocoon strategy, in 2011, the Consensus on Pertussis Booster Vaccination in Europe renewed the recommendation of administering a single dose of Tdap to close contacts of unvaccinated or incompletely vaccinated infants <12 months of age.4

In Italy, the National Vaccination Schedule recommends a primary antipertussis cycle of 3 full doses in the first year of life, with a booster dose at 5–6 years and Tdap booster vaccination at 11–15 years. Further boosters, every 10 years in adult life, are warranted.5

Despite programatic difficulties and some criticism about its efficiency, a cocoon strategy might be feasible. It was advised by the Italian Society of Hygiene, Preventive Medicine and Public Health (SITI) in an immunization schedule for adults, but there is a lack of direction about how to implement it.6

In the Italian healthcare system organization, the Local Health Unit Prevention Department (PD) is devoted to promote health in the population, including programming, managing and performing the immunization service.

The aim of this study was to investigate the opinions of PD Directors regarding the burden of pertussis in adults and infants, the value of the cocoon rationale and the requirements to define the operating procedures and timing for the potential implementation of the cocoon strategy into their own organizational framework.

METHODS

The study received the approval by the Institutional Review Board of the Puglia (Italy) Regional Observatory for Epidemiology and was promoted by the SITI Puglia regional division. A secure web-based survey (www.surveymonkey.com) was created and proposed to all the PD Directors (N = 167). An invitation letter was sent by electronic mail to a list of PD Directors, followed by a once-a-week reminder to nonrespondents.

The questionnaire included 18 questions organized in 4 different sections concerning: the epidemiology and burden of pertussis in Italy; the value of the cocoon rationale and cost-efficacy; the role of PD and other healthcare providers in setting up the cocoon strategy; availability to implement the cocoon strategy locally and estimated timelines.

To answer to each of the first 16 questions, the respondents were asked to cross 1 of the 4 Likert scale boxes encompassing “complete agree, partial agree, partial disagree, complete disagree,” or the box “I don’t know.” Such an answer structure requested to phrase the questions in a affirmative statement shape.

To express the opinions about the operating procedures for introducing cocooning into their own organizational framework, the respondents were asked to indicate the institutional level at which this decision was expected to be made: “national, regional, local, all the previous answers, other—comment field.” The timing of implementation of cocoon was rated as “0–6, 6–12, 12–18 and 18–24 months.”

To assess the possible association between the opinion regarding the cocooning introduction and the perception of the pertussis burden and/or the cocooning rationale among the study population, multiple linear regression analysis was performed, assigning a numeric value to 4 classes of agreement (complete disagree = 1, partial disagree = 2, partial agree = 3, complete agree = 4), excluding “I don’t know” responses.

Significance level was set to <0.05. Data were processed using STATA-MP 10.1 software for Mac OS X (Apple Inc., Cupertino, CA).

RESULTS

From May to October 2011, a total of 106 PD Directors (63.5%) completed the questionnaires; 10% explicitly refused to respond. The sample of respondents includes PDs from each of the Italian regions. The participating PDs represented <50% of the existing PDs in 3 regions, while 100% of PDs took part in the survey in 5 regions. The respondent rate and the incidence of pertussis in 2009 per region do not show a particular pattern of distribution (Fig. 1).FIGURE 1.Proportion of respondents and incidence rate for pertussis (year 2009), per Italian regions.

The degree of agreement with the different items concerning the burden of pertussis, the cocoon rationale and cost-efficacy and the role of healthcare providers in setting up the strategy are summarized in Table (Supplemental Digital Content 1, https://links.lww.com/INF/B305).

Cocoon should be recommended/authorized by the National Health Authority for 25.47%, by the Regional Authority for 82.08% and by the Local Health Units for 35.85% of PD Directors. Nearly one-third (34.91%) of the respondents considered enough an interval of 0–6 months to implement the cocoon strategy, 33.02% judged necessary 6–12 months, 15.09% considered 12–18 months and 6.60% 18–24 months (no answer: 10.38%).

According to the multiple linear regression analysis, the opinion on the prominent role of PDs in promoting and coordinating locally the cocoon strategy (question 11) was positively influenced by a high level of agreement on the items: (1) pertussis is a still common disease in Italian adolescent and adults (question 1; exp(coef) = 1.20, P < 0.05); (2) parents as the primary source of infection in unprotected infants (question 5; exp(coef) = 1.2, P < 0.05); (3) recommendations in other countries and by the SITI (question 7; exp(coef) = 1.61, P = 0.001). The vaccination services function of administering Tdap to close contacts of newborns (question 12) was positively influenced with the knowledge of existing recommendations from other countries and by the SITI (question 7; exp(coef) = 1.70, P = 0.002). The recognized role of general practitioners and family pediatricians in promoting cocooning (question 16) was positively associated with high level of agreement on the cost-effectiveness and cost-saving of the cocoon strategy even if only parents are immunized (question 9; exp(coef) = 1.27, P < 0.05). The judgment that Tdap vaccination should be offered first to parents and afterward to close contacts (question 14) positively correlated with the knowledge of existing recommendations from other countries and by the SITI (question 7; exp(coef) = 1.66, P < 0.05).

DISCUSSION

Qualitative surveys among local decision makers and healthcare workers are considered useful to assess the opinion about the implementation of a new immunization program and its likely impact. Despite the difficulties in performing such studies, the attitude from public health professionals regarding a certain immunization strategy contribute to assess the level of priority and finally support the decision of its implementation.7

This survey is affected by some methodologic limitations: (1) the affirmative style of the questions, imposed by the answer method, could have introduced some bias in the respondents’ perception; (2) the questionnaire was not previously validated and checked for consistency and (3) despite a significant return, the results of the survey cannot be considered representative of the opinions of all the PD Directors.

The scarce availability of official or published data on the incidence or seroprevalence of pertussis across different age classes, due to the underreporting to the passive surveillance system of infectious diseases, could have affected the opinions on the burden of disease.

The level of awareness among respondents on the cocoon value and cost-efficacy seems to be significant. A cost-effective analysis recently carried out in Italy documented that cocoon is cost-effective even when only parents are included.8 Other studies carried out in the Netherlands have demonstrated the cost-effectiveness too.9,10 Other findings, mainly from the United States, reported the cocoon strategy as noncost-effective11 or requiring a very high number of subject to be vaccinated to prevent one pertussis case in newborns.12 This should be taken into account in different epidemiologic and demographic situations (pertussis incidence, number of households and number of contacts).

Respondents awake to maintain vaccinations within the PD organizational framework, due to an existing network of services, professional skills and expertise, which can guarantee an equity offered throughout the Country. The potential role of family pediatricians in reinforcing the communication to the parents to understand the value of cocoon is also acknowledged. More uncertainty comes out from the feasibility of a 2-step implementation strategy. As proposed, offering the cocoon booster only to parents could allow to establish the concept and let the vaccination healthcare providers and family pediatricians become familiar with the strategy; later on, the offer might be extended to all the other contacts.13

Because many respondents agreed that one national policy would be difficult to implement, it can be postulated that in Italy the cocoon strategy may be expected to be implemented at the local level first. Nevertheless, one single national recommendation should be developed to harmonize the behaviors at the regional level and to decrease the inequalities.

FIGURE 1
FIGURE 1:
Proportion of respondents and incidence rate for pertussis (year 2009), per Italian regions.

ACKNOWLEDGMENTS

The authors thank Dr. Filomena Valentina Pollidoro for data collection and her precious assistance during the survey. They are also grateful to Prof. Michele Quarto, Dr. Domenico Lagravinese and Dr. Michele Conversano (SITI Puglia regional division) for having encouraged the study; the Italian Working Group on Cocoon for the discussions and input; all the participating PD Directors for their kind collaboration.

REFERENCES

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10. Westra TA, de Vries R, Tamminga JJ, et al. Cost-effectiveness analysis of various pertussis vaccination strategies primarily aimed at protecting infants in the Netherlands. Clin Ther. 2010;32:1479–1495
11. Centers for Disease Control and Prevention (CDC). . Updated recommendations for use of tetanus toxoid, reduced diphtheria toxoid and acellular pertussis vaccine (Tdap) in pregnant women and persons who have or anticipate having close contact with an infant aged <12 months—Advisory Committee on Immunization Practices (ACIP), 2011. MMWR Morb Mortal Wkly Rep.. 2011;60:1424–1426
12. Skowronski DM, Janjua NZ, Tsafack EP, et al. The number needed to vaccinate to prevent infant pertussis hospitalization and death through parent cocoon immunization. Clin Infect Dis. 2012;54:318–327
13. Ciarrocchi G, Ferrera G, Franco E, et al. Ipotesi di modalità attuative della strategia cocoon in Italia [Poster 298]. In: XXI Conferenza Nazionale di Sanità Pubblica; 2011 Oct 12–15; Roma, It.. 2011 Roma Edizioni Iniziative Sanitarie:p. 500 Available at: http://www.siti2011.org/ita/index.php?option=com_content&view=article&catid=null&id=143:gli-atti. Accessed May 16, 2012
Keywords:

pertussis; vaccines

Supplemental Digital Content

© 2012 Lippincott Williams & Wilkins, Inc.