Invasive Pneumococcal Disease and 7-Valent Pneumococcal Conjugate Vaccine, the Netherlands - - Emerging Infectious Disease journal - CDC
Invasive Pneumococcal Disease and 7-Valent Pneumococcal Conjugate Vaccine, the Netherlands
65 (13%) years of age. A trend toward gradual increases in non–PCV7 serotype IPD infections was observed in all age groups; the largest increases were among persons 50–64 (37%) and >65 (25%) years of age. In adults, the proportion of immunocompromised persons increased among IPD patients. Overall, deaths from IPD decreased from 16% to 12% because of a lower case-fatality rate for persons with non–PCV7 serotype IPD.
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AbstractIn the Netherlands, the national immunization program includes 7-valent pneumococcal conjugate vaccine (PCV7) for all newborns born after April 1, 2006. We compared the incidence of invasive pneumococcal disease (IPD) and patient and disease characteristics before PCV7 introduction (June 2004–June 2006) with those after PCV7 introduction (June 2008–June 2010). Culture-confirmed IPD cases were identified by 9 sentinel laboratories covering ≈25% of the Dutch population. Significant declines in overall IPD incidence were observed in children <2 and="and" class="text-underline" in="in" persons="persons">>2>
Streptococcus pneumoniae is a major cause of severe invasive infections, such as meningitis, invasive pneumonia, and other bloodstream infections. The highest incidence rates for such infections are for infants and elderly persons (1).
Since 2001, many high-income countries included the 7-valent pneumococcal conjugate vaccine (PCV7; Prevenar; Pfizer Pharmaceuticals, Pearl River, NY, USA) in their national immunization programs for newborns (2). In general, within a few years after the introduction of PCV7, the age group targeted for vaccination and unvaccinated adults showed a dramatic decrease in invasive pneumococcal disease (IPD) caused by the 7 vaccine serotypes (2–5). However, at the same time, the incidence of non-PCV7 serotype IPD increased (3,4,6,7).
The overall benefit of PCV7 varies by country, perhaps as a result of differences in surveillance methods and the maturity of vaccination programs (8). For all age groups, the overall reduction in IPD incidence is greater in the United States than in European countries; the great reduction in the United States is a result of a decrease in PCV7-serotype IPD in adults and less replacement of PCV7-serotype by non–PCV7 serotype IPD in children and older adults (3,4,7). The United States began using PCV7 in 2000, but many European countries did not begin using the vaccine until after 2005–2006, and they have experienced less protection from indirect herd protection (herd immunity). Furthermore, not all European countries implemented a catch-up program for children <5 age="age" also="also" before="before" by="by" catch-up="catch-up" caused="caused" circulation="circulation" covered="covered" differences="differences" eradication="eradication" geographic="geographic" href="http://wwwnc.cdc.gov/eid/article/18/11/12-0329_article.htm#r7" implementation="implementation" in="in" ipd="ipd" of="of" pcv7="pcv7" programs="programs" proportion="proportion" relative="relative" routine="routine" serotypes.="serotypes." serotypes="serotypes" speed="speed" the="the" title="7" up="up" vaccination="vaccination" vaccine="vaccine" variations="variations" years="years">75>
In addition, the benefits of vaccination with PCV7 may have been biased, for example, by changes in the directive for blood culture after 2000, as in the United States (9,10), and by enhanced surveillance, as reported for England and Wales (4). Unlike studies in the United States, studies in Europe, particularly Dutch surveillance studies, have focused almost exclusively on patients requiring hospitalization for severe IPD and who often had other underlying illnesses (11,12). This difference in reporting leads to different baseline incidence rates and may affect the observed net benefit of vaccination (13). For example, compared with healthy persons of the same age, US adults with comorbid conditions benefited less from the indirect effects of PCV7 because of an increase in non–PCV7 serotype IPD after introduction of the vaccine (14). Differences in the directive for blood culture and patient populations under surveillance can partly explain the differences in results from use of PCV7.
The invasive disease potential of S. pneumoniae and the population at risk for IPD differs by serotype (12,13,15). Therefore, shifts in circulating serotypes may change the clinical manifestations of IPD, the population segment most at risk for infection, and the disease course and outcome. We investigated these issues and changes in IPD incidence in the Netherlands 4 years after a PCV7 vaccine program was implemented and compared our findings with those from the years just before introduction of the vaccine.