WASHINGTON — Physicians inappropriately delayed giving the third and fourth doses of pneumococcal conjugate vaccine to high-risk children during the 2004 shortage, Stephen M. Tannenbaum, M.D., reported at the National Immunization Conference sponsored by the Centers for Disease Control and Prevention.
During last year's shortfall of 7-valent pneumococcal conjugate vaccine (marketed as Prevnar), the CDC issued two sets of interim guidelines to ensure optimal distribution of available vaccine. First, on Feb. 13, the CDC advised that routine administration of the fourth dose be temporarily suspended for healthy children (MMWR 2004;53:108-9). Then, as manufacturing problems continued, on March 5 the CDC issued another notice calling for suspension of both the third and fourth doses to healthy children (MMWR 2004;53:177-8).
In both documents, the CDC specified that both vaccine doses should be continued in children at high risk for pneumococcal disease, including those with sickle cell disease and other hemoglobinopathies, chronic cardiac or pulmonary disease, diabetes, and HIV or other immunosuppressive conditions.
However, a review of Southern California Kaiser Permanente's Immunization Tracking System—which contains more than 3 million current members plus previous members—revealed that physicians were withholding the doses equally among high- and low-risk children, said Dr. Tannenbaum, a staff pediatrician at Kaiser Permanente, Los Angeles.
The review covered all doses of pneumococcal conjugate vaccine (PCV) administered by 437 pediatricians and 706 family physicians to children younger than 17 months of age during January-December 2004. The study had a birth cohort design: For each month, 2,073-3,180 healthy children and 0-37 high-risk children turned 3, 5, 7, and 16 months of age. Among the 633 high-risk children, the most common ICD-9 diagnoses listed were congenital heart anomalies (77%), sickle cell anemia (5%), and pulmonary conditions (4.5%), he reported.
Coverage for the first dose—assessed at 3 months of age—remained consistently high for both groups throughout 2004, in the 90% -95% range for low-risk children, and close to 100% for high-risk children. Coverage rates dropped slightly for the second dose, measured at 5 months, but remained relatively high in both groups throughout the year.
Following the first CDC notice, coverage rates for dose 4—measured at 16 months of age—dropped slowly and similarly in both high- and low-risk groups. By May, receipt of the fourth dose was nearly identical in both groups, at 41% of high-risk and 45% of low-risk children. By the time the CDC reinstated dose 4 on Sept. 17, coverage was just 6% for the high-risk and 4% for low-risk children, said Dr. Tannenbaum, who conducted the study with Maureen S. Kolasa, R.N., of the CDC.
Physicians were quicker in withholding dose 3 when that recommendation came out. Overall coverage—measured at 7 months—dropped from 55% in March to just 15% in April. It continued to fall to a low of 7% in June before rising again after the CDC reinstated it on July 9.
Although dose 3 coverage was slightly greater for high-risk vs. low-risk children during the period of its deferral, at no time were the differences significant. In April, for example, only 19% of high-risk children received dose 3, compared with 15% of low-risk children. In May, while the proportion of low-risk children receiving dose 3 dropped to just 8%, it remained at only 19% among the high-risk children, Dr. Tannenbaum reported.
By December 2004, after resumption of all doses, coverage had still not returned to preshortage levels, at just 16% of low-risk and 25% of high-risk children for dose 4, and 68% and 69%, respectively, for dose 3.