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      Vaccine herd effect


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          Vaccination ideally protects susceptible populations at high risk for complications of the infection. However, vaccines for these subgroups do not always provide sufficient effectiveness. The herd effect or herd immunity is an attractive way to extend vaccine benefits beyond the directly targeted population. It refers to the indirect protection of unvaccinated persons, whereby an increase in the prevalence of immunity by the vaccine prevents circulation of infectious agents in susceptible populations. The herd effect has had a major impact in the eradication of smallpox, has reduced transmission of pertussis, and protects against influenza and pneumococcal disease. A high uptake of vaccines is generally needed for success. In this paper we aim to provide an update review on the herd effect, focusing on the clinical benefit, by reviewing data for specific vaccines.

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          Efficacy of human papillomavirus (HPV)-16/18 AS04-adjuvanted vaccine against cervical infection and precancer caused by oncogenic HPV types (PATRICIA): final analysis of a double-blind, randomised study in young women

          The Lancet, 374(9686), 301-314
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            Worldwide prevalence and genotype distribution of cervical human papillomavirus DNA in women with normal cytology: a meta-analysis.

            We set out to estimate the age and genotype-specific prevalence of cervical human papillomavirus (HPV) DNA in women with normal cervical cytology worldwide by meta-analysis of a systematic literature review. Reports on HPV prevalence published between January, 1995, and January, 2005, were retrieved. To be included, studies required information on cervical cytology, plus detailed descriptions of study populations, methods used to collect cervical samples, and assays used for HPV DNA detection and typing. Final analyses included 78 studies that could be separated into women with normal cytology, and of which subsets of 44 and 48 studies had data on age and type-specific HPV prevalence, respectively. Overall HPV prevalence in 157 879 women with normal cervical cytology was estimated to be 10.4% (95% CI 10.2-10.7). Corresponding estimates by region were Africa 22.1% (20.9-23.4), Central America and Mexico 20.4% (19.3-21.4), northern America 11.3% (10.6-12.1), Europe 8.1% (7.8-8.4), and Asia 8.0% (7.5-8.4). In all world regions, HPV prevalence was highest in women younger than 35 years of age, decreasing in women of older age. In Africa, the Americas, and Europe, a clear second peak of HPV prevalence was observed in women aged 45 years or older. On the basis of these estimates, around 291 million women worldwide are carriers of HPV DNA, of whom 32% are infected with HPV16 or HPV18, or both. The HPV types most commonly detected are similar to those most commonly described in pre-neoplastic and cancer cases, although the relative contribution of HPV16 and HPV18 is substantially lower in cytologically normal women.
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              Safety and efficacy of a pentavalent human-bovine (WC3) reassortant rotavirus vaccine.

              Rotavirus is a leading cause of childhood gastroenteritis and death worldwide. We studied healthy infants approximately 6 to 12 weeks old who were randomly assigned to receive three oral doses of live pentavalent human-bovine (WC3 strain) reassortant rotavirus vaccine containing human serotypes G1, G2, G3, G4, and P[8] or placebo at 4-to-10-week intervals in a blinded fashion. Active surveillance was used to identify subjects with serious adverse and other events. The 34,035 infants in the vaccine group and 34,003 in the placebo group were monitored for serious adverse events. Intussusception occurred in 12 vaccine recipients and 15 placebo recipients within one year after the first dose including six vaccine recipients and five placebo recipients within 42 days after any dose (relative risk, 1.6; 95 percent confidence interval, 0.4 to 6.4). The vaccine reduced hospitalizations and emergency department visits related to G1-G4 rotavirus gastroenteritis occurring 14 or more days after the third dose by 94.5 percent (95 percent confidence interval, 91.2 to 96.6 percent). In a nested substudy, efficacy against any G1-G4 rotavirus gastroenteritis through the first full rotavirus season after vaccination was 74.0 percent (95 percent confidence interval, 66.8 to 79.9 percent); efficacy against severe gastroenteritis was 98.0 percent (95 percent confidence interval, 88.3 to 100 percent). The vaccine reduced clinic visits for G1-G4 rotavirus gastroenteritis by 86.0 percent (95 percent confidence interval, 73.9 to 92.5 percent). This vaccine was efficacious in preventing rotavirus gastroenteritis, decreasing severe disease and health care contacts. The risk of intussusception was similar in vaccine and placebo recipients. (ClinicalTrials.gov number, NCT00090233.) Copyright 2006 Massachusetts Medical Society.

                Author and article information

                Scand J Infect Dis
                Scandinavian Journal of Infectious Diseases
                Informa Healthcare
                September 2011
                23 May 2011
                : 43
                : 9
                : 683-689
                [1 ]Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario, Canada
                [2 ]Division of Infectious Diseases, Departments of Internal Medicine, Soon Chun Hyang University, Seoul Hospital, Seoul, Republic of Korea
                [3 ]Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, Hamilton, Ontario, Canada
                [4 ]Department of Medicine, McMaster University, Hamilton, Ontario, Canada
                Author notes
                Correspondence: M. Loeb, Michael G. DeGroote Centre for Learning, Rm 3203, McMaster University Faculty of Health Sciences, 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada. Tel:+ 1 905 525 9140 ext. 26066. Fax: + 1 905 389 5822. E-mail: loebm@ 123456mcmaster.ca
                © 2011 Informa Healthcare

                This is an open access article distributed under the Supplemental Terms and Conditions for iOpenAccess articles published in Informa Healthcare journals , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                : 25 February 2011
                : 14 April 2011
                Review Article

                Infectious disease & Microbiology
                vaccine herd immunity,vaccine herd effect
                Infectious disease & Microbiology
                vaccine herd immunity, vaccine herd effect


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