Examination of reports from the first two years after licensure of a new vaccine against pneumococcal infections indicates that the majority of adverse effects are minor, but that continued surveillance is warranted, according to a study in the October 13 issue of JAMA.
The Food and Drug Administration (FDA) licensed the 7-valent pneumococcal conjugate vaccine (PCV, trade name Prevnar) on February 17, 2000, according to background information in the article. The recommended vaccination series includes doses at ages 2, 4, 6, and 12 to 15 months, with catch-up doses through 9 years of age. Pneumococcal conjugate vaccine has been rapidly adopted into routine pediatric practice, reflecting concern for the gravity of serious pneumococcal infections (such as meningitis or pneumonia) and confidence in the efficacy and safety of PCV.
Prior to licensure, almost 19,000 infants and children received PCV in randomized clinical trials that demonstrated good efficacy against invasive infections and a favorable safety profile. However, rare vaccine complications may not emerge before licensure for a variety of reasons, particularly the relatively limited sample sizes of trials.
Robert P. Wise, M.D., M.P.H., of the Food and Drug Administration, Rockville, Md., and colleagues analyzed the summary of data from the Vaccine Adverse Event Reporting System (VAERS), a national passive surveillance database, in the first 2 years after PCV licensure. Reports studied were for children younger than 18 years and vaccinated with PCV.
The researchers found that a total of 4,154 reports of events following PCV were submitted to VAERS, for a rate of 13.2 reports per 100,000 doses distributed. Multiple vaccines were given in 74.3 percent of reports. The most frequently reported symptoms and signs included fever, injection site reactions, fussiness and rashes. Serious events were described in 14.6 percent of reports (a rate similar to that for other vaccines), including 117 deaths and 34 cases of invasive pneumococcal infections possibly representing vaccine failure. Neurological symptoms occurred in 38 percent of reports. Seizures were described in 393 reports.
"In the first 2 years after PCV licensure, the great majority of VAERS reports portray minor adverse events already observed during clinical trials. Our focused follow-up of the first 98 seizure reports addressed a concern arising from the prelicensure trial. We found that the large majority of reported seizures were febrile [fever-related] or in patients with a previous history of seizures. Although allergic reactions, prolonged or abnormal crying, fussiness in infants, dyspnea [breathing difficulties], and GI distress are common childhood symptoms apart from immunizations, their occurrence with positive rechallenges after PCV increases the possibility of occasional causal relationship with vaccination and, therefore, warrants continued surveillance for these events," the authors write.