Protection for Pediatric Tx Patients

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7-valent pneumococcal vaccine is immunogenic, safe, and well tolerated, Canadian study shows.

 

The 7-valent pneumococcal conjugate vaccine (Prevnar) is safe and well tolerated in pediatric solid-organ transplant recipients, according to researchers at the Hospital for Sick Children in Toronto. The vaccine was immunogenic against most vaccine-containing serotypes.

 

“Pneumococcal infections have been found to be one of the leading causes of serious bacterial infections in solid-organ transplant recipients,” said investigator Michelle Barton-Forbes, MD. “Preventive strategies such as immunization are clearly important. In the past, the 23-valent [vaccine] was the only vaccine available; however, it had limitations with age and adequacy of responsiveness in these patients. Our findings support the use of this [7-valent] vaccine in this special population. Additionally, there appear to be enhanced responses when the vaccine is followed by a dose of the 23-valent vaccine.”

 

The results should be reassuring for nephrologists who manage pediatric kidney transplants, said Dr. Barton-Forbes, who is an infectious disease fellow. Until, now, it was uncertain what the potential risks and benefits were in using vaccines in pediatric kidney recipients. It is well established that the 7-valent pneumococcal conjugate vaccine is safe and immunogenic in healthy children, but little published data are available regarding its use in transplant recipients, who are known to be at elevated risk for severe pneumococcal infections.

 

The researchers, led by senior investigator Upton Allen, MD, studied the 7-valent vaccine in 82 transplant recipients (31 cardiac, 27 renal, 19 liver, and 5 lung). Three doses of vaccine were given eight weeks apart; eight to 12 weeks after the third dose, patients received the 23-valent vaccine.

 

The patients, who had a mean age of 8.5 years, were vaccinated at a median time of 1.4 years post-transplantation (range 0.34-5.5 years). Following 230 doses of the 7-valent vaccine, there were no vaccine-related severe adverse events and virtually no adverse effects at all associated with 72% of the doses. The most common adverse events were mild local reactions, which occurred after 19.1% of doses, most often in cardiac patients.

 

Among the 31 cardiac recipients, serotypes 19F, 14, and 6B were the most immunogenic and achieved geometric median concentrations of 6.59, 6.40 and 3.76 mg/mL, respectively, after dose 3. Overall, in the cardiac recipients, the conjugate vaccine series resulted in antibody titers of greater than twofold above baseline for 5 serotypes. In addition, the 23-valent vaccine boosted the two non-responding serotypes (14 and 19F) in 50% of the cases. Antibody titers that exceed 0.15 mg/mL are considered protective. For the purposes of the study, an adequate response to the vaccine was defined as a greater than twofold increase in baseline antibody titers.

 

Dr. Barton-Forbes concluded that, “The findings from this study, one of the largest we are aware of, provide reassuring news that not only is the vaccine safe, but that it is able to induce responses in these immunosuppressed children.”

 

A study published in Pediatric Transplantation (2005;9:183-186) found that invasive neumococcal disease in pediatric transplant patients occurs at an annual rate of 176 episodes per 100,000 children, compared with 35-68 episodes per 100,000 for generally healthy children younger than five years.

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