Study Confirms Prevnar® Effectiveness in Curtailing Ear Infections

Newswise — After nearly eradicating invasive pneumococcal disease in a vaccine study population, the heptavalent pneumococcal conjugate vaccine PCV7 or Prevnar®, manufactured by Wyeth-Ayerst, was licensed in February, 2000, for use in children older than six weeks. The vaccine has demonstrated an excellent safety profile with swelling and erythema (redness due to capillary dilation) being the most common side effects. The seven serotypes [explain] covered by PCV7 are responsible for 83 percent of invasive disease in American children younger than four, contributing to its overwhelming success. These serotypes are also known to be the most antibiotic resistant.

Unfortunately, the ability of PCV7 to prevent pneumococcal otitis media (ear infection) has not been as conclusive. This is important. Otitis media (OM) remains a significant burden to children, health care providers, and society. This childhood disorder is the most frequent reason for pediatric office visits in the United States accounting for approximately 20 million visits annually. By one year of age, 62 percent of children will have had one episode of otitis media; at age three years of age, 83 percent will have had at least one episode. In total, one half of all children will have at least three episodes of otitis media. The most common pathogen for acute otitis media is Streptococcus pneumoniae, responsible for 30 to 50 percent of all cases. The quest for a vaccine for Streptococcus pneumoniae has been difficult due to the more than 90 different serotypes of the bacteria with each having a polysaccharide capsule. Younger children have an immature immune system; hence are unable to mount a lasting T-cell-independent response to invasive bacterial disease.

The introduction of PCV7 generated disappointing results regarding its efficacy against otitis media. Additionally, there has been a national shortage of the vaccine making it difficult to immunize children according to the 2, 4, 6 and 12 to 15 month schedule prompting a modified two-dose vaccination schedule. Furthermore, PCV7 is the most expensive vaccine on the market today with an average cost of $46 - $58.

A new study sought to evaluate the effectiveness of PCV7 in preventing otitis media and whether the number of doses given had any effect on the rate of ear infections in a university clinic population. This study, "The First Class of Prevnar Vaccinated Children and Otitis Media: How Did They Do?" was authored by Emily E Epstein, MD, from St. Louis University, Saint Louis, MO. Her findings will be presented at presented at the 107th meeting of The Triological Society http://www.triological.org, being held April 30 - May 3, 2004, at the JW Marriott Desert Ridge Resort & Spa, Phoenix, AZ.

Methodology: A retrospective chart review of children receiving care in a university pediatric clinic at Cardinal Glennon Children's Hospital (CGCH), Saint Louis, Missouri was conducted. A study group and a historical control group were evaluated. The control group consisted of children born after January 1, 1995, having received no doses of Prevnar. The study group consisted of children born between September 1, 1999 and March 31, 2002, who had received at least two doses of Prevnar® with the first dose administered before age six months. Charts of children born during these periods were randomly reviewed. To be included in the study, the patients must have received all of their well child check ups at CGCH with up-to-date immunizations. Children with craniofacial abnormalities or immunocompromised states were excluded. Information recorded included the child's date of birth, sex, gestation, number of siblings, race, attendance at day care, history of breast feeding, associated comorbidities, and the number and dates of Prevnar administration as well as otitis media history. An episode lasting more than 30 days was counted as one episode if there was documentation that the infection or effusion had not resolved. Emergency room visits at CGCH and clinic visits were reviewed.

The patient demographics were compared using appropriate chi square and t-tests. The mean number of episodes of OM between the control (no Prevnar) and study groups (2-4 doses Prevnar) were compared with ANOVA and appropriate post-hoc tests. Additionally, a regression model was tested using explanatory variables (day care, breast feeding, number siblings, race, and gender). The ANOVA and regression analysis were stratified to OM observed under age three and OM observed under age two for each child.

Results: A total of 263 children were included in the study. Of the 263 children, 153 were in the study group and 110 were in the control group. Except for an increased probability of Prevnar children to be breast-fed, there were no significant differences in the demographic characteristics or the risk factors for OM between the two groups. Key findings included: · Two or more doses of Prevnar® have a protective effect against otitis media. However, more than two doses did not provide a statistically significant reduction in the incidence of OM under age two or three.· Vaccinated children were more likely to never have a first episode of otitis media.· Children vaccinated with Prevnar® had a statistically significant decrease in the number of physician visits for otitis media and a decrease in complicated ear infection.· Children in both the control and study groups enrolled in daycare had more episodes of OM, consistent with other studies of children in daycare.· Sixty-five percent of the study population received less than the recommended four vaccines due to the vaccine shortage. While this study only included the most compliant children, many children in a university clinic population miss well child exams and hence have delayed immunizations.

Conclusions: Children in this study received less than the full vaccination series, likely had unreported episodes of OM, and had many different treating physicians with differing levels of experience and definitions of otitis media. The findings reveal that for children in a university clinic setting, two doses of Prevnar® or more reduces the number of episodes of OM, the number of complications related to OM, and the number of related office visits. Larger scale review is needed and this study population needs to be followed for a longer period of time.